v3.15.0

fix corner case in inline (#5311 )
fixes #5222
2022-01-26 01:33:13 +08:00 · 2022-01-26 00:47:24 +08:00 · 2022-01-23 00:45:11 +08:00 · 2022-01-21 09:40:33 +08:00 · 2022-01-21 05:13:26 +08:00 · 2022-01-19 08:14:19 +08:00
110 changed files with 21502 additions and 3793 deletions
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -8,7 +8,12 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        options: [ '-mb braces', '--ie8 -c', '-mc', '--toplevel -mc passes=3,pure_getters,unsafe' ]
+        options:
+          - '-mb braces'
+          - '--ie -c'
+          - '-mc'
+          - '-p acorn --toplevel -mco spidermonkey'
+          - '--toplevel -mc passes=3,pure_getters,unsafe'
        script:
          - acorn.sh
          - bootstrap.sh
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,14 +7,9 @@ jobs:
  test:
    strategy:
      matrix:
-        node: [ '0.8', '0.10', '0.12', '4', '6', '8', '10', '12', '14', latest ]
+        node: [ '0.10', '0.12', '4', '6', '8', '10', '12', '14', '16', latest ]
        os: [ ubuntu-latest, windows-latest ]
        script: [ compress, mocha, release/benchmark, release/jetstream ]
-        exclude:
-          - node: '0.8'
-            script: release/benchmark
-          - node: '0.8'
-            script: release/jetstream
    name: ${{ matrix.node }} ${{ matrix.os }} ${{ matrix.script }}
    runs-on: ${{ matrix.os }}
    env:
--- a/.github/workflows/ufuzz.yml
+++ b/.github/workflows/ufuzz.yml
@@ -2,11 +2,14 @@ name: Fuzzing
 on:
  pull_request:
  schedule:
-    - cron: '*/5 * * * *'
+    - cron: '*/15 * * * *'
+  workflow_dispatch:
+  workflow_run:
+    branches: [ master ]
+    types: [ completed ]
+    workflows: [ 'Build testing', CI ]
 env:
  BASE_URL: https://api.github.com/repos/${{ github.repository }}
-  CAUSE: ${{ github.event_name }}
-  RUN_NUM: ${{ github.run_number }}
  TOKEN: ${{ github.token }}
 jobs:
  ufuzz:
@@ -34,8 +37,8 @@ jobs:
        shell: bash
        run: |
          . ./test/release/install.sh
-          if [[ $CAUSE == "schedule" ]]; then
-            node test/ufuzz/job $BASE_URL $TOKEN $RUN_NUM
-          else
+          if [[ $GITHUB_EVENT_NAME == "pull_request" ]]; then
            node test/ufuzz/job 5000
+          else
+            node test/ufuzz/job $BASE_URL $TOKEN $GITHUB_RUN_NUMBER
          fi
--- a/README.md
+++ b/README.md
@@ -111,10 +111,11 @@ a double dash to prevent input files being used as option arguments:
    -d, --define <expr>[=value] Global definitions.
    -e, --enclose [arg[:value]] Embed everything in a big function, with configurable
                                argument(s) & value(s).
-    --ie8                       Support non-standard Internet Explorer 8.
-                                Equivalent to setting `ie8: true` in `minify()`
+    --ie                        Support non-standard Internet Explorer.
+                                Equivalent to setting `ie: true` in `minify()`
                                for `compress`, `mangle` and `output` options.
                                By default UglifyJS will not try to be IE-proof.
+    --keep-fargs                Do not mangle/drop function arguments.
    --keep-fnames               Do not mangle/drop function names.  Useful for
                                code relying on Function.prototype.name.
    --name-cache <file>         File to hold mangled name mappings.
@@ -502,7 +503,10 @@ if (result.error) throw result.error;
 - `compress` (default: `{}`) — pass `false` to skip compressing entirely.
  Pass an object to specify custom [compress options](#compress-options).

- `ie8` (default: `false`) — set to `true` to support IE8.
+- `ie` (default: `false`) — enable workarounds for Internet Explorer bugs.
+
+- `keep_fargs` (default: `false`) — pass `true` to prevent discarding or mangling
+  of function arguments.

 - `keep_fnames` (default: `false`) — pass `true` to prevent discarding or mangling
  of function names.  Useful for code relying on `Function.prototype.name`.
@@ -566,7 +570,6 @@ if (result.error) throw result.error;
    },
    nameCache: null, // or specify a name cache object
    toplevel: false,
-    ie8: false,
    warnings: false,
 }
 ```
@@ -708,7 +711,8 @@ to be `false` and all symbol names will be omitted.
  - `1` — inline simple functions
  - `2` — inline functions with arguments
  - `3` — inline functions with arguments and variables
-  - `true` — same as `3`
+  - `4` — inline functions with arguments, variables and statements
+  - `true` — same as `4`

 - `join_vars` (default: `true`) — join consecutive `var` statements

@@ -795,9 +799,8 @@ to be `false` and all symbol names will be omitted.
  variables (`"vars"`) in the top level scope (`false` by default, `true` to drop
  both unreferenced functions and variables)

- `typeofs` (default: `true`) — Transforms `typeof foo == "undefined"` into
-  `foo === void 0`.  Note: recommend to set this value to `false` for IE10 and
-  earlier versions due to known issues.
+- `typeofs` (default: `true`) — compress `typeof` expressions, e.g.
+  `typeof foo == "undefined" → void 0 === foo`

 - `unsafe` (default: `false`) — apply "unsafe" transformations (discussion below)

@@ -869,6 +872,9 @@ UglifyJS.minify(code, { mangle: { toplevel: true } }).code;
 - `debug` (default: `false`) — Mangle names with the original name still present.
  Pass an empty string `""` to enable, or a non-empty string to set the debug suffix.

+- `keep_fargs` (default: `false`) — Use `true` to prevent mangling of function
+  arguments.
+
 - `keep_quoted` (default: `false`) — Only mangle unquoted property names.

 - `regex` (default: `null`) — Pass a RegExp literal to only mangle property
@@ -1201,6 +1207,17 @@ To allow for better optimizations, the compiler makes various assumptions:
 - Object properties can be added, removed and modified (not prevented with
  `Object.defineProperty()`, `Object.defineProperties()`, `Object.freeze()`,
  `Object.preventExtensions()` or `Object.seal()`).
+- If array destructuring is present, index-like properties in `Array.prototype`
+  have not been overridden:
+  ```javascript
+  Object.prototype[0] = 42;
+  var [ a ] = [];
+  var { 0: b } = {};
+  // 42 undefined
+  console.log([][0], a);
+  // 42 42
+  console.log({}[0], b);
+  ```
 - Earlier versions of JavaScript will throw `SyntaxError` with the following:
  ```javascript
  ({
@@ -1309,3 +1326,48 @@ To allow for better optimizations, the compiler makes various assumptions:
  // Actual:   { '42': undefined }
  ```
  UglifyJS may modify the input which in turn may suppress those errors.
+- Later versions of JavaScript will throw `SyntaxError` with the following:
+  ```javascript
+  var await;
+  async function f() {
+      class A {
+          static p = await;
+      }
+  }
+  // SyntaxError: Unexpected reserved word
+  ```
+  UglifyJS may modify the input which in turn may suppress those errors.
+- Later versions of JavaScript will throw `SyntaxError` with the following:
+  ```javascript
+  var async;
+  for (async of []);
+  // SyntaxError: The left-hand side of a for-of loop may not be 'async'.
+  ```
+  UglifyJS may modify the input which in turn may suppress those errors.
+- Later versions of Chrome and Node.js will give incorrect results with the
+  following:
+  ```javascript
+  console.log({
+      ...console,
+      get 42() {
+          return "FAIL";
+      },
+      [42]: "PASS",
+  }[42]);
+  // Expected: "PASS"
+  // Actual:   "FAIL"
+  ```
+  UglifyJS may modify the input which in turn may suppress those errors.
+- Earlier versions of JavaScript will throw `TypeError` with the following:
+  ```javascript
+  (function() {
+      {
+          const a = "foo";
+      }
+      {
+          const a = "bar";
+      }
+  })();
+  // TypeError: const 'a' has already been declared
+  ```
+  UglifyJS may modify the input which in turn may suppress those errors.
--- a/bin/uglifyjs
+++ b/bin/uglifyjs
@@ -10,7 +10,9 @@ var info = require("../package.json");
 var path = require("path");
 var UglifyJS = require("../tools/node");

-var skip_keys = [ "cname", "fixed", "inlined", "parent_scope", "scope", "uses_eval", "uses_with" ];
+var skip_keys = [ "cname", "fixed", "in_arg", "inlined", "length_read", "parent_scope", "redef", "scope", "unused" ];
+var truthy_keys = [ "optional", "pure", "terminal", "uses_arguments", "uses_eval", "uses_with" ];
+
 var files = {};
 var options = {};
 var short_forms = {
@@ -70,6 +72,7 @@ function process_option(name, no_value) {
                } else {
                    if (padding.length < name.length) padding = Array(name.length + 1).join(" ");
                    toplevels.push([ {
+                        keep_fargs: "keep-fargs",
                        keep_fnames: "keep-fnames",
                        nameCache: "name-cache",
                    }[name] || name, option ]);
@@ -101,7 +104,8 @@ function process_option(name, no_value) {
                "  --config-file <file>                     Read minify() options from JSON file.",
                "  -d, --define <expr>[=value]              Global definitions.",
                "  -e, --enclose [arg[,...][:value[,...]]]  Embed everything in a big function, with configurable argument(s) & value(s).",
-                "  --ie8                                    Support non-standard Internet Explorer 8.",
+                "  --ie                                     Support non-standard Internet Explorer.",
+                "  --keep-fargs                             Do not mangle/drop function arguments.",
                "  --keep-fnames                            Do not mangle/drop function names. Useful for code relying on Function.prototype.name.",
                "  --name-cache <file>                      File to hold mangled name mappings.",
                "  --rename                                 Force symbol expansion.",
@@ -110,6 +114,7 @@ function process_option(name, no_value) {
                "  --source-map [options]                   Enable source map/specify source map options.",
                "  --timings                                Display operations run time on STDERR.",
                "  --toplevel                               Compress and/or mangle variables in toplevel scope.",
+                "  --v8                                     Support non-standard Chrome & Node.js.",
                "  --validate                               Perform validation during AST manipulations.",
                "  --verbose                                Print diagnostic messages.",
                "  --warn                                   Print warning messages.",
@@ -145,9 +150,11 @@ function process_option(name, no_value) {
        options[name] = read_value();
        break;
      case "annotations":
+      case "ie":
      case "ie8":
      case "timings":
      case "toplevel":
+      case "v8":
      case "validate":
      case "webkit":
        options[name] = true;
@@ -155,6 +162,9 @@ function process_option(name, no_value) {
      case "no-annotations":
        options.annotations = false;
        break;
+      case "keep-fargs":
+        options.keep_fargs = true;
+        break;
      case "keep-fnames":
        options.keep_fnames = true;
        break;
@@ -235,10 +245,11 @@ if (options.mangle && options.mangle.properties) {
        });
    }
 }
-if (output == "ast") options.output = {
-    ast: true,
-    code: false,
-};
+if (/^ast|spidermonkey$/.test(output)) {
+    if (typeof options.output != "object") options.output = {};
+    options.output.ast = true;
+    options.output.code = false;
+}
 if (options.parse && (options.parse.acorn || options.parse.spidermonkey)
    && options.sourceMap && options.sourceMap.content == "inline") {
    fatal("inline source map only works with built-in parser");
@@ -265,7 +276,9 @@ if (specified["self"]) {
    paths = UglifyJS.FILES;
 }
 if (specified["in-situ"]) {
-    if (output || specified["reduce-test"] || specified["self"]) fatal("incompatible options specified");
+    if (output && output != "spidermonkey" || specified["reduce-test"] || specified["self"]) {
+        fatal("incompatible options specified");
+    }
    paths.forEach(function(name) {
        print(name);
        if (/^ast|spidermonkey$/.test(name)) fatal("invalid file name specified");
@@ -311,13 +324,43 @@ function run() {
    try {
        if (options.parse) {
            if (options.parse.acorn) {
+                var annotations = Object.create(null);
                files = convert_ast(function(toplevel, name) {
-                    return require("acorn").parse(files[name], {
+                    var content = files[name];
+                    var list = annotations[name] = [];
+                    var prev = -1;
+                    return require("acorn").parse(content, {
+                        allowHashBang: true,
+                        ecmaVersion: "latest",
                        locations: true,
+                        onComment: function(block, text, start, end) {
+                            var match = /[@#]__PURE__/.exec(text);
+                            if (!match) {
+                                if (start != prev) return;
+                                match = [ list[prev] ];
+                            }
+                            while (/\s/.test(content[end])) end++;
+                            list[end] = match[0];
+                            prev = end;
+                        },
+                        preserveParens: true,
                        program: toplevel,
-                        sourceFile: name
+                        sourceFile: name,
+                        sourceType: "module",
                    });
                });
+                files.walk(new UglifyJS.TreeWalker(function(node) {
+                    if (!(node instanceof UglifyJS.AST_Call)) return;
+                    var list = annotations[node.start.file];
+                    var pure = list[node.start.pos];
+                    if (!pure) {
+                        var tokens = node.start.parens;
+                        if (tokens) for (var i = 0; !pure && i < tokens.length; i++) {
+                            pure = list[tokens[i].pos];
+                        }
+                    }
+                    if (pure) node.pure = pure;
+                }));
            } else if (options.parse.spidermonkey) {
                files = convert_ast(function(toplevel, name) {
                    var obj = JSON.parse(files[name]);
@@ -394,7 +437,7 @@ function run() {
              case "thedef":
                return symdef(value);
            }
-            if (skip_key(key)) return;
+            if (skip_property(key, value)) return;
            if (value instanceof UglifyJS.AST_Token) return;
            if (value instanceof UglifyJS.Dictionary) return;
            if (value instanceof UglifyJS.AST_Node) {
@@ -409,16 +452,19 @@ function run() {
            return value;
        }, 2));
    } else if (output == "spidermonkey") {
-        print(JSON.stringify(UglifyJS.minify(result.code, {
-            compress: false,
-            mangle: false,
-            output: {
-                ast: true,
-                code: false
-            },
-        }).ast.to_mozilla_ast(), null, 2));
+        print(JSON.stringify(result.ast.to_mozilla_ast(), null, 2));
    } else if (output) {
-        fs.writeFileSync(output, result.code);
+        var code;
+        if (result.ast) {
+            var opts = {};
+            for (var name in options.output) {
+                if (!/^ast|code$/.test(name)) opts[name] = options.output[name];
+            }
+            code = UglifyJS.AST_Node.from_mozilla_ast(result.ast.to_mozilla_ast()).print_to_string(opts);
+        } else {
+            code = result.code;
+        }
+        fs.writeFileSync(output, code);
        if (result.map) fs.writeFileSync(output + ".map", result.map);
    } else {
        print(result.code);
@@ -480,7 +526,7 @@ function read_file(path, default_value) {
 }

 function parse_js(value, options, flag) {
-    if (!options || typeof options != "object") options = {};
+    if (!options || typeof options != "object") options = Object.create(null);
    if (typeof value == "string") try {
        UglifyJS.parse(value, {
            expression: true
@@ -520,8 +566,10 @@ function parse_js(value, options, flag) {
    return options;
 }

-function skip_key(key) {
-    return skip_keys.indexOf(key) >= 0;
+function skip_property(key, value) {
+    return skip_keys.indexOf(key) >= 0
+        // only skip truthy_keys if their value is falsy
+        || truthy_keys.indexOf(key) >= 0 && !value;
 }

 function symdef(def) {
--- a/lib/ast.js
+++ b/lib/ast.js
@@ -50,41 +50,39 @@ function DEFNODE(type, props, methods, base) {
    if (base && base.PROPS) props = props.concat(base.PROPS);
    var code = [
        "return function AST_", type, "(props){",
+        // not essential, but speeds up compress by a few percent
+        "this._bits=0;",
        "if(props){",
    ];
    props.forEach(function(prop) {
        code.push("this.", prop, "=props.", prop, ";");
    });
    code.push("}");
-    var proto = base && new base;
-    if (proto && proto.initialize || methods && methods.initialize) code.push("this.initialize();");
-    code.push("}");
+    var proto = Object.create(base && base.prototype);
+    if (methods.initialize || proto.initialize) code.push("this.initialize();");
+    code.push("};");
    var ctor = new Function(code.join(""))();
-    if (proto) {
-        ctor.prototype = proto;
-        ctor.BASE = base;
-    }
-    if (base) base.SUBCLASSES.push(ctor);
+    ctor.prototype = proto;
    ctor.prototype.CTOR = ctor;
-    ctor.PROPS = props || null;
-    ctor.SELF_PROPS = self_props;
-    ctor.SUBCLASSES = [];
-    if (type) {
-        ctor.prototype.TYPE = ctor.TYPE = type;
-    }
-    if (methods) for (var name in methods) if (HOP(methods, name)) {
-        if (/^\$/.test(name)) {
-            ctor[name.substr(1)] = methods[name];
-        } else {
-            ctor.prototype[name] = methods[name];
-        }
+    ctor.prototype.TYPE = ctor.TYPE = type;
+    if (base) {
+        ctor.BASE = base;
+        base.SUBCLASSES.push(ctor);
    }
    ctor.DEFMETHOD = function(name, method) {
        this.prototype[name] = method;
    };
-    if (typeof exports !== "undefined") {
-        exports["AST_" + type] = ctor;
+    ctor.PROPS = props;
+    ctor.SELF_PROPS = self_props;
+    ctor.SUBCLASSES = [];
+    for (var name in methods) if (HOP(methods, name)) {
+        if (/^\$/.test(name)) {
+            ctor[name.substr(1)] = methods[name];
+        } else {
+            ctor.DEFMETHOD(name, methods[name]);
+        }
    }
+    if (typeof exports !== "undefined") exports["AST_" + type] = ctor;
    return ctor;
 }

@@ -139,6 +137,53 @@ var AST_Node = DEFNODE("Node", "start end", {
    },
 }, null);

+DEF_BITPROPS(AST_Node, [
+    "_optimized",
+    "_squeezed",
+    // AST_Call
+    "call_only",
+    // AST_Lambda
+    "collapse_scanning",
+    // AST_SymbolRef
+    "defined",
+    "evaluating",
+    "falsy",
+    // AST_SymbolRef
+    "in_arg",
+    // AST_Return
+    "in_bool",
+    // AST_SymbolRef
+    "is_undefined",
+    // AST_LambdaExpression
+    // AST_LambdaDefinition
+    "inlined",
+    // AST_Lambda
+    "length_read",
+    // AST_Yield
+    "nested",
+    // AST_Lambda
+    "new",
+    // AST_Call
+    // AST_PropAccess
+    "optional",
+    // AST_ClassProperty
+    "private",
+    // AST_Call
+    "pure",
+    // AST_Assign
+    "redundant",
+    // AST_ClassProperty
+    "static",
+    // AST_Call
+    // AST_PropAccess
+    "terminal",
+    "truthy",
+    // AST_Scope
+    "uses_eval",
+    // AST_Scope
+    "uses_with",
+]);
+
 (AST_Node.log_function = function(fn, verbose) {
    if (typeof fn != "function") {
        AST_Node.info = AST_Node.warn = noop;
@@ -257,13 +302,13 @@ var AST_SimpleStatement = DEFNODE("SimpleStatement", "body", {
    },
 }, AST_Statement);

-var AST_BlockScope = DEFNODE("BlockScope", "enclosed functions make_def parent_scope variables", {
+var AST_BlockScope = DEFNODE("BlockScope", "_var_names enclosed functions make_def parent_scope variables", {
    $documentation: "Base class for all statements introducing a lexical scope",
    $propdoc: {
        enclosed: "[SymbolDef*/S] a list of all symbol definitions that are accessed from this scope or any subscopes",
-        functions: "[Object/S] like `variables`, but only lists function declarations",
+        functions: "[Dictionary/S] like `variables`, but only lists function declarations",
        parent_scope: "[AST_Scope?/S] link to the parent scope",
-        variables: "[Object/S] a map of name ---> SymbolDef for all variables/functions defined in this scope",
+        variables: "[Dictionary/S] a map of name ---> SymbolDef for all variables/functions defined in this scope",
    },
    clone: function(deep) {
        var node = this._clone(deep);
@@ -488,7 +533,7 @@ var AST_With = DEFNODE("With", "expression", {

 /* -----[ scope and functions ]----- */

-var AST_Scope = DEFNODE("Scope", "uses_eval uses_with", {
+var AST_Scope = DEFNODE("Scope", "fn_defs may_call_this uses_eval uses_with", {
    $documentation: "Base class for all statements introducing a lexical scope",
    $propdoc: {
        uses_eval: "[boolean/S] tells whether this scope contains a direct call to the global `eval`",
@@ -506,7 +551,7 @@ var AST_Scope = DEFNODE("Scope", "uses_eval uses_with", {
 var AST_Toplevel = DEFNODE("Toplevel", "globals", {
    $documentation: "The toplevel scope",
    $propdoc: {
-        globals: "[Object/S] a map of name ---> SymbolDef for all undeclared names",
+        globals: "[Dictionary/S] a map of name ---> SymbolDef for all undeclared names",
    },
    wrap: function(name) {
        var body = this.body;
@@ -547,13 +592,13 @@ var AST_Toplevel = DEFNODE("Toplevel", "globals", {
    }
 }, AST_Scope);

-var AST_Lambda = DEFNODE("Lambda", "argnames length_read rest uses_arguments", {
+var AST_Lambda = DEFNODE("Lambda", "argnames length_read rest safe_ids uses_arguments", {
    $documentation: "Base class for functions",
    $propdoc: {
        argnames: "[(AST_DefaultValue|AST_Destructured|AST_SymbolFunarg)*] array of function arguments and/or destructured literals",
        length_read: "[boolean/S] whether length property of this function is accessed",
        rest: "[(AST_Destructured|AST_SymbolFunarg)?] rest parameter, or null if absent",
-        uses_arguments: "[boolean/S] whether this function accesses the arguments array",
+        uses_arguments: "[boolean|number/S] whether this function accesses the arguments array",
    },
    each_argname: function(visit) {
        var tw = new TreeWalker(function(node) {
@@ -1293,11 +1338,14 @@ function must_be_expressions(node, prop, allow_spread, allow_hole) {
    });
 }

-var AST_Call = DEFNODE("Call", "expression args pure", {
+var AST_Call = DEFNODE("Call", "args expression optional pure terminal", {
    $documentation: "A function call expression",
    $propdoc: {
+        args: "[AST_Node*] array of arguments",
        expression: "[AST_Node] expression to invoke as function",
-        args: "[AST_Node*] array of arguments"
+        optional: "[boolean] whether the expression is optional chaining",
+        pure: "[boolean/S] marker for side-effect-free call expression",
+        terminal: "[boolean] whether the chain has ended",
    },
    walk: function(visitor) {
        var node = this;
@@ -1315,7 +1363,11 @@ var AST_Call = DEFNODE("Call", "expression args pure", {
 });

 var AST_New = DEFNODE("New", null, {
-    $documentation: "An object instantiation.  Derives from a function call since it has exactly the same properties"
+    $documentation: "An object instantiation.  Derives from a function call since it has exactly the same properties",
+    _validate: function() {
+        if (this.optional) throw new Error("optional must be false");
+        if (this.terminal) throw new Error("terminal must be false");
+    },
 }, AST_Call);

 var AST_Sequence = DEFNODE("Sequence", "expressions", {
@@ -1337,22 +1389,23 @@ var AST_Sequence = DEFNODE("Sequence", "expressions", {
    },
 });

-var AST_PropAccess = DEFNODE("PropAccess", "expression property", {
+function root_expr(prop) {
+    while (prop instanceof AST_PropAccess) prop = prop.expression;
+    return prop;
+}
+
+var AST_PropAccess = DEFNODE("PropAccess", "expression optional property terminal", {
    $documentation: "Base class for property access expressions, i.e. `a.foo` or `a[\"foo\"]`",
    $propdoc: {
        expression: "[AST_Node] the “container” expression",
-        property: "[AST_Node|string] the property to access.  For AST_Dot this is always a plain string, while for AST_Sub it's an arbitrary AST_Node"
+        optional: "[boolean] whether the expression is optional chaining",
+        property: "[AST_Node|string] the property to access.  For AST_Dot this is always a plain string, while for AST_Sub it's an arbitrary AST_Node",
+        terminal: "[boolean] whether the chain has ended",
    },
-    getProperty: function() {
+    get_property: function() {
        var p = this.property;
-        if (p instanceof AST_Constant) {
-            return p.value;
-        }
-        if (p instanceof AST_UnaryPrefix
-            && p.operator == "void"
-            && p.expression instanceof AST_Constant) {
-            return;
-        }
+        if (p instanceof AST_Constant) return p.value;
+        if (p instanceof AST_UnaryPrefix && p.operator == "void" && p.expression instanceof AST_Constant) return;
        return p;
    },
    _validate: function() {
@@ -1485,6 +1538,12 @@ var AST_Assign = DEFNODE("Assign", null, {
                    throw new Error("left must be assignable: " + node.TYPE);
                }
            });
+        } else if (!(this.left instanceof AST_Infinity
+            || this.left instanceof AST_NaN
+            || this.left instanceof AST_PropAccess && !this.left.optional
+            || this.left instanceof AST_SymbolRef
+            || this.left instanceof AST_Undefined)) {
+            throw new Error("left must be assignable");
        }
    },
 }, AST_Binary);
@@ -1686,7 +1745,7 @@ var AST_ObjectMethod = DEFNODE("ObjectMethod", null, {
    _validate: function() {
        if (!(this.value instanceof AST_LambdaExpression)) throw new Error("value must be AST_LambdaExpression");
        if (is_arrow(this.value)) throw new Error("value cannot be AST_Arrow or AST_AsyncArrow");
-        if (this.value.name != null) throw new Error("name of class method's lambda must be null");
+        if (this.value.name != null) throw new Error("name of object method's lambda must be null");
    },
 }, AST_ObjectKeyVal);

@@ -1743,7 +1802,7 @@ var AST_SymbolVar = DEFNODE("SymbolVar", null, {
    $documentation: "Symbol defining a variable",
 }, AST_SymbolDeclaration);

-var AST_SymbolFunarg = DEFNODE("SymbolFunarg", null, {
+var AST_SymbolFunarg = DEFNODE("SymbolFunarg", "unused", {
    $documentation: "Symbol naming a function argument",
 }, AST_SymbolVar);

@@ -1757,11 +1816,11 @@ var AST_SymbolLambda = DEFNODE("SymbolLambda", null, {

 var AST_SymbolDefClass = DEFNODE("SymbolDefClass", null, {
    $documentation: "Symbol defining a class",
-}, AST_SymbolLet);
+}, AST_SymbolConst);

 var AST_SymbolClass = DEFNODE("SymbolClass", null, {
    $documentation: "Symbol naming a class expression",
-}, AST_SymbolLet);
+}, AST_SymbolConst);

 var AST_SymbolCatch = DEFNODE("SymbolCatch", null, {
    $documentation: "Symbol naming the exception in catch",
@@ -1919,27 +1978,27 @@ var AST_Atom = DEFNODE("Atom", null, {

 var AST_Null = DEFNODE("Null", null, {
    $documentation: "The `null` atom",
-    value: null
+    value: null,
 }, AST_Atom);

 var AST_NaN = DEFNODE("NaN", null, {
    $documentation: "The impossible value",
-    value: 0/0
+    value: 0/0,
 }, AST_Atom);

 var AST_Undefined = DEFNODE("Undefined", null, {
    $documentation: "The `undefined` value",
-    value: function(){}()
+    value: function(){}(),
 }, AST_Atom);

 var AST_Hole = DEFNODE("Hole", null, {
    $documentation: "A hole in an array",
-    value: function(){}()
+    value: function(){}(),
 }, AST_Atom);

 var AST_Infinity = DEFNODE("Infinity", null, {
    $documentation: "The `Infinity` value",
-    value: 1/0
+    value: 1/0,
 }, AST_Atom);

 var AST_Boolean = DEFNODE("Boolean", null, {
@@ -1951,12 +2010,12 @@ var AST_Boolean = DEFNODE("Boolean", null, {

 var AST_False = DEFNODE("False", null, {
    $documentation: "The `false` atom",
-    value: false
+    value: false,
 }, AST_Boolean);

 var AST_True = DEFNODE("True", null, {
    $documentation: "The `true` atom",
-    value: true
+    value: true,
 }, AST_Boolean);

 /* -----[ TreeWalker ]----- */
@@ -1995,7 +2054,7 @@ TreeWalker.prototype = {
    },
    find_parent: function(type) {
        var stack = this.stack;
-        for (var i = stack.length; --i >= 0;) {
+        for (var i = stack.length - 1; --i >= 0;) {
            var x = stack[i];
            if (x instanceof type) return x;
        }
--- a/lib/compress.js
+++ b/lib/compress.js
--- a/lib/minify.js
+++ b/lib/minify.js
@@ -28,7 +28,7 @@ function read_source_map(name, toplevel) {
        var match = /^# ([^\s=]+)=(\S+)\s*$/.exec(comment.value);
        if (!match) break;
        if (match[1] == "sourceMappingURL") {
-            match = /^data:application\/json(;.*?)?;base64,(\S+)$/.exec(match[2]);
+            match = /^data:application\/json(;.*?)?;base64,([^,]+)$/.exec(match[2]);
            if (!match) break;
            return to_ascii(match[2]);
        }
@@ -76,7 +76,9 @@ function minify(files, options) {
            annotations: undefined,
            compress: {},
            enclose: false,
+            ie: false,
            ie8: false,
+            keep_fargs: false,
            keep_fnames: false,
            mangle: {},
            nameCache: null,
@@ -96,17 +98,20 @@ function minify(files, options) {
        var timings = options.timings && { start: Date.now() };
        if (options.rename === undefined) options.rename = options.compress && options.mangle;
        if (options.annotations !== undefined) set_shorthand("annotations", options, [ "compress", "output" ]);
-        if (options.ie8) set_shorthand("ie8", options, [ "compress", "mangle", "output" ]);
+        if (options.ie8) options.ie = options.ie || options.ie8;
+        if (options.ie) set_shorthand("ie", options, [ "compress", "mangle", "output" ]);
+        if (options.keep_fargs) set_shorthand("keep_fargs", options, [ "compress", "mangle" ]);
        if (options.keep_fnames) set_shorthand("keep_fnames", options, [ "compress", "mangle" ]);
        if (options.toplevel) set_shorthand("toplevel", options, [ "compress", "mangle" ]);
        if (options.v8) set_shorthand("v8", options, [ "mangle", "output" ]);
-        if (options.webkit) set_shorthand("webkit", options, [ "mangle", "output" ]);
+        if (options.webkit) set_shorthand("webkit", options, [ "compress", "mangle", "output" ]);
        var quoted_props;
        if (options.mangle) {
            options.mangle = defaults(options.mangle, {
                cache: options.nameCache && (options.nameCache.vars || {}),
                eval: false,
-                ie8: false,
+                ie: false,
+                keep_fargs: false,
                keep_fnames: false,
                properties: false,
                reserved: [],
@@ -204,27 +209,29 @@ function minify(files, options) {
        if (options.mangle && options.mangle.properties) mangle_properties(toplevel, options.mangle.properties);
        if (timings) timings.output = Date.now();
        var result = {};
-        if (options.output.ast) {
-            result.ast = toplevel;
-        }
-        if (!HOP(options.output, "code") || options.output.code) {
+        var output = defaults(options.output, {
+            ast: false,
+            code: true,
+        });
+        if (output.ast) result.ast = toplevel;
+        if (output.code) {
            if (options.sourceMap) {
-                options.output.source_map = SourceMap(options.sourceMap);
+                output.source_map = SourceMap(options.sourceMap);
                if (options.sourceMap.includeSources) {
                    if (files instanceof AST_Toplevel) {
                        throw new Error("original source content unavailable");
                    } else for (var name in files) if (HOP(files, name)) {
-                        options.output.source_map.setSourceContent(name, files[name]);
+                        output.source_map.setSourceContent(name, files[name]);
                    }
                }
            }
-            delete options.output.ast;
-            delete options.output.code;
-            var stream = OutputStream(options.output);
+            delete output.ast;
+            delete output.code;
+            var stream = OutputStream(output);
            toplevel.print(stream);
            result.code = stream.get();
            if (options.sourceMap) {
-                result.map = options.output.source_map.toString();
+                result.map = output.source_map.toString();
                var url = options.sourceMap.url;
                if (url) {
                    result.code = result.code.replace(/\n\/\/# sourceMappingURL=\S+\s*$/, "");
--- a/lib/mozilla-ast.js
+++ b/lib/mozilla-ast.js
--- a/lib/output.js
+++ b/lib/output.js
@@ -49,8 +49,6 @@ function is_some_comments(comment) {
 }

 function OutputStream(options) {
-
-    var readonly = !options;
    options = defaults(options, {
        annotations      : false,
        ascii_only       : false,
@@ -58,7 +56,7 @@ function OutputStream(options) {
        braces           : false,
        comments         : false,
        galio            : false,
-        ie8              : false,
+        ie               : false,
        indent_level     : 4,
        indent_start     : 0,
        inline_script    : true,
@@ -103,12 +101,35 @@ function OutputStream(options) {
        }
    }

-    var indentation = options.indent_start;
    var current_col = 0;
    var current_line = 1;
    var current_pos = 0;
-    var OUTPUT = "";
+    var indentation = options.indent_start;
+    var last;
+    var line_end = 0;
+    var line_fixed = true;
+    var mappings = options.source_map && [];
+    var mapping_name;
+    var mapping_token;
+    var might_need_space;
+    var might_need_semicolon;
+    var need_newline_indented = false;
+    var need_space = false;
+    var newline_insert = -1;
+    var stack;
+    var OUTPUT;

+    function reset() {
+        last = "";
+        might_need_space = false;
+        might_need_semicolon = false;
+        stack = [];
+        var str = OUTPUT;
+        OUTPUT = "";
+        return str;
+    }
+
+    reset();
    var to_utf8 = options.ascii_only ? function(str, identifier) {
        if (identifier) str = str.replace(/[\ud800-\udbff][\udc00-\udfff]/g, function(ch) {
            return "\\u{" + (ch.charCodeAt(0) - 0xd7c0 << 10 | ch.charCodeAt(1) - 0xdc00).toString(16) + "}";
@@ -141,6 +162,25 @@ function OutputStream(options) {
        return j == 0 ? str : s + str.slice(j);
    };

+    function quote_single(str) {
+        return "'" + str.replace(/\x27/g, "\\'") + "'";
+    }
+
+    function quote_double(str) {
+        return '"' + str.replace(/\x22/g, '\\"') + '"';
+    }
+
+    var quote_string = [
+        null,
+        quote_single,
+        quote_double,
+        function(str, quote) {
+            return quote == "'" ? quote_single(str) : quote_double(str);
+        },
+    ][options.quote_style] || function(str, quote, dq, sq) {
+        return dq > sq ? quote_single(str) : quote_double(str);
+    };
+
    function make_string(str, quote) {
        var dq = 0, sq = 0;
        str = str.replace(/[\\\b\f\n\r\v\t\x22\x27\u2028\u2029\0\ufeff]/g, function(s, i) {
@@ -153,7 +193,7 @@ function OutputStream(options) {
              case "\t": return "\\t";
              case "\b": return "\\b";
              case "\f": return "\\f";
-              case "\x0B": return options.ie8 ? "\\x0B" : "\\v";
+              case "\x0B": return options.ie ? "\\x0B" : "\\v";
              case "\u2028": return "\\u2028";
              case "\u2029": return "\\u2029";
              case "\ufeff": return "\\ufeff";
@@ -162,54 +202,11 @@ function OutputStream(options) {
            }
            return s;
        });
-        function quote_single() {
-            return "'" + str.replace(/\x27/g, "\\'") + "'";
-        }
-        function quote_double() {
-            return '"' + str.replace(/\x22/g, '\\"') + '"';
-        }
-        str = to_utf8(str);
-        switch (options.quote_style) {
-          case 1:
-            return quote_single();
-          case 2:
-            return quote_double();
-          case 3:
-            return quote == "'" ? quote_single() : quote_double();
-          default:
-            return dq > sq ? quote_single() : quote_double();
-        }
-    }
-
-    function encode_string(str, quote) {
-        var ret = make_string(str, quote);
-        if (options.inline_script) {
-            ret = ret.replace(/<\x2f(script)([>\/\t\n\f\r ])/gi, "<\\/$1$2");
-            ret = ret.replace(/\x3c!--/g, "\\x3c!--");
-            ret = ret.replace(/--\x3e/g, "--\\x3e");
-        }
-        return ret;
-    }
-
-    function make_name(name) {
-        name = name.toString();
-        name = to_utf8(name, true);
-        return name;
+        return quote_string(to_utf8(str), quote, dq, sq);
    }

    /* -----[ beautification/minification ]----- */

-    var has_parens = false;
-    var line_end = 0;
-    var line_fixed = true;
-    var might_need_space = false;
-    var might_need_semicolon = false;
-    var need_newline_indented = false;
-    var need_space = false;
-    var newline_insert = -1;
-    var last = "";
-    var mapping_token, mapping_name, mappings = options.source_map && [];
-
    var adjust_mappings = mappings ? function(line, col) {
        mappings.forEach(function(mapping) {
            mapping.line += line;
@@ -257,8 +254,14 @@ function OutputStream(options) {

    var requireSemicolonChars = makePredicate("( [ + * / - , .");

-    function print(str) {
-        str = String(str);
+    var print = options.beautify
+        || options.comments
+        || options.max_line_len
+        || options.preserve_line
+        || options.shebang
+        || !options.semicolons
+        || options.source_map
+        || options.width ? function(str) {
        var ch = str.charAt(0);
        if (need_newline_indented && ch) {
            need_newline_indented = false;
@@ -328,7 +331,6 @@ function OutputStream(options) {
        }

        OUTPUT += str;
-        has_parens = str.slice(-1) == "(";
        current_pos += str.length;
        var a = str.split(/\r?\n/), n = a.length - 1;
        current_line += n;
@@ -338,7 +340,30 @@ function OutputStream(options) {
            current_col = a[n].length;
        }
        last = str;
-    }
+    } : function(str) {
+        var ch = str.charAt(0);
+        var prev = last.slice(-1);
+        if (might_need_semicolon) {
+            might_need_semicolon = false;
+            if (prev == ":" && ch == "}" || (!ch || ";}".indexOf(ch) < 0) && prev != ";") {
+                OUTPUT += ";";
+                might_need_space = false;
+            }
+        }
+        if (might_need_space) {
+            if (is_identifier_char(prev) && (is_identifier_char(ch) || ch == "\\")
+                || (ch == "/" && ch == prev)
+                || ((ch == "+" || ch == "-") && ch == last)
+                || str == "--" && last == "!"
+                || str == "in" && prev == "/"
+                || last == "--" && ch == ">") {
+                OUTPUT += " ";
+            }
+            if (prev != "<" || str != "!") might_need_space = false;
+        }
+        OUTPUT += str;
+        last = str;
+    };

    var space = options.beautify ? function() {
        print(" ");
@@ -351,14 +376,12 @@ function OutputStream(options) {
        print(repeat_string(" ", half ? indentation - (options.indent_level >> 1) : indentation));
    } : noop;

-    var with_indent = options.beautify ? function(col, cont) {
-        if (col === true) col = next_indent();
+    var with_indent = options.beautify ? function(cont) {
        var save_indentation = indentation;
-        indentation = col;
-        var ret = cont();
+        indentation += options.indent_level;
+        cont();
        indentation = save_indentation;
-        return ret;
-    } : function(col, cont) { return cont() };
+    } : function(cont) { cont() };

    var may_add_newline = options.max_line_len || options.preserve_line ? function() {
        fix_line();
@@ -387,41 +410,28 @@ function OutputStream(options) {
        print(";");
    }

-    function next_indent() {
-        return indentation + options.indent_level;
-    }
-
    function with_block(cont) {
-        var ret;
        print("{");
        newline();
-        with_indent(next_indent(), function() {
-            ret = cont();
-        });
+        with_indent(cont);
        indent();
        print("}");
-        return ret;
    }

    function with_parens(cont) {
        print("(");
        may_add_newline();
-        //XXX: still nice to have that for argument lists
-        //var ret = with_indent(current_col, cont);
-        var ret = cont();
+        cont();
        may_add_newline();
        print(")");
-        return ret;
    }

    function with_square(cont) {
        print("[");
        may_add_newline();
-        //var ret = with_indent(current_col, cont);
-        var ret = cont();
+        cont();
        may_add_newline();
        print("]");
-        return ret;
    }

    function comma() {
@@ -472,31 +482,37 @@ function OutputStream(options) {
        return true;
    }

+    function should_merge_comments(node, parent) {
+        if (parent instanceof AST_Binary) return parent.left === node;
+        if (parent.TYPE == "Call") return parent.expression === node;
+        if (parent instanceof AST_Conditional) return parent.condition === node;
+        if (parent instanceof AST_Dot) return parent.expression === node;
+        if (parent instanceof AST_Exit) return true;
+        if (parent instanceof AST_Sequence) return parent.expressions[0] === node;
+        if (parent instanceof AST_Sub) return parent.expression === node;
+        if (parent instanceof AST_UnaryPostfix) return true;
+        if (parent instanceof AST_Yield) return true;
+    }
+
    function prepend_comments(node) {
        var self = this;
-        var scan = node instanceof AST_Exit && node.value;
+        var scan;
+        if (node instanceof AST_Exit) {
+            scan = node.value;
+        } else if (node instanceof AST_Yield) {
+            scan = node.expression;
+        }
        var comments = dump(node);
        if (!comments) comments = [];

        if (scan) {
            var tw = new TreeWalker(function(node) {
-                var parent = tw.parent();
-                if (parent instanceof AST_Exit
-                    || parent instanceof AST_Binary && parent.left === node
-                    || parent.TYPE == "Call" && parent.expression === node
-                    || parent instanceof AST_Conditional && parent.condition === node
-                    || parent instanceof AST_Dot && parent.expression === node
-                    || parent instanceof AST_Sequence && parent.expressions[0] === node
-                    || parent instanceof AST_Sub && parent.expression === node
-                    || parent instanceof AST_UnaryPostfix) {
-                    var before = dump(node);
-                    if (before) comments = comments.concat(before);
-                } else {
-                    return true;
-                }
+                if (!should_merge_comments(node, tw.parent())) return true;
+                var before = dump(node);
+                if (before) comments = comments.concat(before);
            });
            tw.push(node);
-            node.value.walk(tw);
+            scan.walk(tw);
        }

        if (current_pos == 0) {
@@ -505,9 +521,7 @@ function OutputStream(options) {
                indent();
            }
            var preamble = options.preamble;
-            if (preamble) {
-                print(preamble.replace(/\r\n?|[\n\u2028\u2029]|\s*$/g, "\n"));
-            }
+            if (preamble) print(preamble.replace(/\r\n?|\u2028|\u2029|(^|\S)\s*$/g, "$1\n"));
        }

        comments = comments.filter(comment_filter, node);
@@ -553,15 +567,14 @@ function OutputStream(options) {
        if (OUTPUT.length > insert) newline_insert = insert;
    }

-    var stack = [];
    return {
        get             : get,
-        toString        : get,
+        reset           : reset,
        indent          : indent,
-        should_break    : readonly ? noop : function() {
-            return options.width && current_col - indentation >= options.width;
-        },
-        has_parens      : function() { return has_parens },
+        should_break    : options.width ? function() {
+            return current_col - indentation >= options.width;
+        } : return_false,
+        has_parens      : function() { return last.slice(-1) == "(" },
        newline         : newline,
        print           : print,
        space           : space,
@@ -571,20 +584,21 @@ function OutputStream(options) {
        semicolon       : semicolon,
        force_semicolon : force_semicolon,
        to_utf8         : to_utf8,
-        print_name      : function(name) { print(make_name(name)) },
-        print_string    : function(str, quote) { print(encode_string(str, quote)) },
-        next_indent     : next_indent,
+        print_name      : function(name) { print(to_utf8(name.toString(), true)) },
+        print_string    : options.inline_script ? function(str, quote) {
+            str = make_string(str, quote).replace(/<\x2f(script)([>\/\t\n\f\r ])/gi, "<\\/$1$2");
+            print(str.replace(/\x3c!--/g, "\\x3c!--").replace(/--\x3e/g, "--\\x3e"));
+        } : function(str, quote) {
+            print(make_string(str, quote));
+        },
        with_indent     : with_indent,
        with_block      : with_block,
        with_parens     : with_parens,
        with_square     : with_square,
        add_mapping     : add_mapping,
        option          : function(opt) { return options[opt] },
-        prepend_comments: readonly ? noop : prepend_comments,
-        append_comments : readonly || comment_filter === return_false ? noop : append_comments,
-        line            : function() { return current_line },
-        col             : function() { return current_col },
-        pos             : function() { return current_pos },
+        prepend_comments: options.comments || options.shebang ? prepend_comments : noop,
+        append_comments : options.comments ? append_comments : noop,
        push_node       : function(node) { stack.push(node) },
        pop_node        : options.preserve_line ? function() {
            var node = stack.pop();
@@ -629,10 +643,19 @@ function OutputStream(options) {
            stream.append_comments(self);
        }
    });
+    var readonly = OutputStream({
+        inline_script: false,
+        shebang: false,
+        width: false,
+    });
    AST_Node.DEFMETHOD("print_to_string", function(options) {
-        var s = OutputStream(options);
-        this.print(s);
-        return s.get();
+        if (options) {
+            var stream = OutputStream(options);
+            this.print(stream);
+            return stream.get();
+        }
+        this.print(readonly);
+        return readonly.reset();
    });

    /* -----[ PARENTHESES ]----- */
@@ -684,6 +707,8 @@ function OutputStream(options) {
        // (x++)[y]
        // (typeof x).y
        if (p instanceof AST_PropAccess) return p.expression === this;
+        // (~x)`foo`
+        if (p instanceof AST_Template) return p.tag === this;
    }
    PARENS(AST_Await, needs_parens_unary);
    PARENS(AST_Unary, needs_parens_unary);
@@ -757,39 +782,50 @@ function OutputStream(options) {
        if (p instanceof AST_Class) return true;
        // (foo && bar)["prop"], (foo && bar).prop
        if (p instanceof AST_PropAccess) return p.expression === this;
+        // (foo && bar)``
+        if (p instanceof AST_Template) return p.tag === this;
        // typeof (foo && bar)
        if (p instanceof AST_Unary) return true;
    });

+    function need_chain_parens(node, parent) {
+        if (!node.terminal) return false;
+        if (!(parent instanceof AST_Call || parent instanceof AST_PropAccess)) return false;
+        return parent.expression === node;
+    }
+
    PARENS(AST_PropAccess, function(output) {
        var node = this;
        var p = output.parent();
-        if (p instanceof AST_New && p.expression === node) {
-            // i.e. new (foo().bar)
-            //
-            // if there's one call into this subtree, then we need
-            // parens around it too, otherwise the call will be
-            // interpreted as passing the arguments to the upper New
-            // expression.
-            do {
-                node = node.expression;
-            } while (node instanceof AST_PropAccess);
-            return node.TYPE == "Call";
-        }
+        // i.e. new (foo().bar)
+        //
+        // if there's one call into this subtree, then we need
+        // parens around it too, otherwise the call will be
+        // interpreted as passing the arguments to the upper New
+        // expression.
+        if (p instanceof AST_New && p.expression === node && root_expr(node).TYPE == "Call") return true;
+        // (foo?.bar)()
+        // (foo?.bar).baz
+        // new (foo?.bar)()
+        return need_chain_parens(node, p);
    });

    PARENS(AST_Call, function(output) {
+        var node = this;
        var p = output.parent();
-        if (p instanceof AST_New) return p.expression === this;
+        if (p instanceof AST_New) return p.expression === node;
        // https://bugs.webkit.org/show_bug.cgi?id=123506
-        if (output.option("webkit")) {
+        if (output.option("webkit")
+            && node.expression instanceof AST_Function
+            && p instanceof AST_PropAccess
+            && p.expression === node) {
            var g = output.parent(1);
-            return this.expression instanceof AST_Function
-                && p instanceof AST_PropAccess
-                && p.expression === this
-                && g instanceof AST_Assign
-                && g.left === p;
+            if (g instanceof AST_Assign && g.left === p) return true;
        }
+        // (foo?.())()
+        // (foo?.()).bar
+        // new (foo?.())()
+        return need_chain_parens(node, p);
    });

    PARENS(AST_New, function(output) {
@@ -915,7 +951,7 @@ function OutputStream(options) {
    });
    function print_braced_empty(self, output) {
        output.print("{");
-        output.with_indent(output.next_indent(), function() {
+        output.with_indent(function() {
            output.append_comments(self, true);
        });
        output.print("}");
@@ -936,7 +972,6 @@ function OutputStream(options) {
    DEFPRINT(AST_Do, function(output) {
        var self = this;
        output.print("do");
-        output.space();
        make_block(self.body, output);
        output.space();
        output.print("while");
@@ -953,7 +988,6 @@ function OutputStream(options) {
        output.with_parens(function() {
            self.condition.print(output);
        });
-        output.space();
        force_statement(self.body, output);
    });
    DEFPRINT(AST_For, function(output) {
@@ -983,7 +1017,6 @@ function OutputStream(options) {
                self.step.print(output);
            }
        });
-        output.space();
        force_statement(self.body, output);
    });
    function print_for_enum(prefix, infix) {
@@ -998,7 +1031,6 @@ function OutputStream(options) {
                output.space();
                self.object.print(output);
            });
-            output.space();
            force_statement(self.body, output);
        };
    }
@@ -1012,7 +1044,6 @@ function OutputStream(options) {
        output.with_parens(function() {
            self.expression.print(output);
        });
-        output.space();
        force_statement(self.body, output);
    });
    DEFPRINT(AST_ExportDeclaration, function(output) {
@@ -1119,8 +1150,9 @@ function OutputStream(options) {
        });
    }
    function print_arrow(self, output) {
-        if (self.argnames.length == 1 && self.argnames[0] instanceof AST_SymbolFunarg && !self.rest) {
-            self.argnames[0].print(output);
+        var argname = self.argnames.length == 1 && !self.rest && self.argnames[0];
+        if (argname instanceof AST_SymbolFunarg && argname.name != "yield") {
+            argname.print(output);
        } else {
            print_funargs(self, output);
        }
@@ -1251,7 +1283,7 @@ function OutputStream(options) {
    function make_then(self, output) {
        var b = self.body;
        if (output.option("braces") && !(b instanceof AST_Const || b instanceof AST_Let)
-            || output.option("ie8") && b instanceof AST_Do)
+            || output.option("ie") && b instanceof AST_Do)
            return make_block(b, output);
        // The squeezer replaces "block"-s that contain only a single
        // statement with the statement itself; technically, the AST
@@ -1281,16 +1313,16 @@ function OutputStream(options) {
        output.with_parens(function() {
            self.condition.print(output);
        });
-        output.space();
        if (self.alternative) {
            make_then(self, output);
            output.space();
            output.print("else");
-            output.space();
-            if (self.alternative instanceof AST_If)
+            if (self.alternative instanceof AST_If) {
+                output.space();
                self.alternative.print(output);
-            else
+            } else {
                force_statement(self.alternative, output);
+            }
        } else {
            force_statement(self.body, output);
        }
@@ -1431,7 +1463,7 @@ function OutputStream(options) {
            parent = output.parent(level++);
            if (parent instanceof AST_Call && parent.expression === node) return;
        } while (parent instanceof AST_PropAccess && parent.expression === node);
-        output.print("/*" + self.pure + "*/");
+        output.print("/*@__PURE__*/");
    }
    function print_call_args(self, output) {
        if (self.expression instanceof AST_Call || self.expression instanceof AST_Lambda) {
@@ -1448,6 +1480,7 @@ function OutputStream(options) {
        var self = this;
        print_annotation(self, output);
        self.expression.print(output);
+        if (self.optional) output.print("?.");
        print_call_args(self, output);
    });
    DEFPRINT(AST_New, function(output) {
@@ -1475,27 +1508,24 @@ function OutputStream(options) {
        var expr = self.expression;
        expr.print(output);
        var prop = self.property;
-        if (output.option("ie8") && RESERVED_WORDS[prop]) {
-            output.print("[");
+        if (output.option("ie") && RESERVED_WORDS[prop]) {
+            output.print(self.optional ? "?.[" : "[");
            output.add_mapping(self.end);
            output.print_string(prop);
            output.print("]");
        } else {
-            if (expr instanceof AST_Number && expr.value >= 0) {
-                if (!/[xa-f.)]/i.test(output.last())) {
-                    output.print(".");
-                }
-            }
-            output.print(".");
+            if (expr instanceof AST_Number && !/[ex.)]/i.test(output.last())) output.print(".");
+            output.print(self.optional ? "?." : ".");
            // the name after dot would be mapped about here.
            output.add_mapping(self.end);
            output.print_name(prop);
        }
    });
    DEFPRINT(AST_Sub, function(output) {
-        this.expression.print(output);
-        output.print("[");
-        this.property.print(output);
+        var self = this;
+        self.expression.print(output);
+        output.print(self.optional ? "?.[" : "[");
+        self.property.print(output);
        output.print("]");
    });
    DEFPRINT(AST_Spread, function(output) {
@@ -1592,7 +1622,19 @@ function OutputStream(options) {
        var self = this;
        var key = print_property_key(self, output);
        var value = self.value;
-        if (key && value instanceof AST_SymbolDeclaration && key == get_symbol_name(value)) return;
+        if (key) {
+            if (value instanceof AST_DefaultValue) {
+                if (value.name instanceof AST_Symbol && key == get_symbol_name(value.name)) {
+                    output.space();
+                    output.print("=");
+                    output.space();
+                    value.value.print(output);
+                    return;
+                }
+            } else if (value instanceof AST_Symbol) {
+                if (key == get_symbol_name(value)) return;
+            }
+        }
        output.colon();
        value.print(output);
    });
@@ -1641,28 +1683,21 @@ function OutputStream(options) {

    function print_property_key(self, output) {
        var key = self.key;
-        if (key instanceof AST_Node) {
-            output.with_square(function() {
-                key.print(output);
-            });
-        } else if (output.option("quote_keys")) {
-            output.print_string(key);
+        if (key instanceof AST_Node) return output.with_square(function() {
+            key.print(output);
+        });
+        var quote = self.start && self.start.quote;
+        if (output.option("quote_keys") || quote && output.option("keep_quoted_props")) {
+            output.print_string(key, quote);
        } else if ("" + +key == key && key >= 0) {
            output.print(make_num(key));
+        } else if (self.private) {
+            output.print_name(key);
+        } else if (RESERVED_WORDS[key] ? !output.option("ie") : is_identifier_string(key)) {
+            output.print_name(key);
+            return key;
        } else {
-            var quote = self.start && self.start.quote;
-            if (self.private) {
-                output.print_name(key);
-            } else if (RESERVED_WORDS[key] ? !output.option("ie8") : is_identifier_string(key)) {
-                if (quote && output.option("keep_quoted_props")) {
-                    output.print_string(key, quote);
-                } else {
-                    output.print_name(key);
-                    return key;
-                }
-            } else {
-                output.print_string(key, quote);
-            }
+            output.print_string(key, quote);
        }
    }
    DEFPRINT(AST_ObjectKeyVal, function(output) {
@@ -1735,7 +1770,7 @@ function OutputStream(options) {
        output.print("`");
    });
    DEFPRINT(AST_Constant, function(output) {
-        output.print(this.value);
+        output.print("" + this.value);
    });
    DEFPRINT(AST_String, function(output) {
        output.print_string(this.value, this.quote);
@@ -1791,9 +1826,10 @@ function OutputStream(options) {
    function force_statement(stat, output) {
        if (output.option("braces") && !(stat instanceof AST_Const || stat instanceof AST_Let)) {
            make_block(stat, output);
-        } else if (!stat || stat instanceof AST_EmptyStatement) {
+        } else if (stat instanceof AST_EmptyStatement) {
            output.force_semicolon();
        } else {
+            output.space();
            stat.print(output);
        }
    }
@@ -1832,8 +1868,8 @@ function OutputStream(options) {
            len = match[0].length;
            digits = str.slice(len);
            candidates.push(digits + "e-" + (digits.length + len - 1));
-        } else if (match = /0+$/.exec(str)) {
-            len = match[0].length;
+        } else if (match = /[^0]0+$/.exec(str)) {
+            len = match[0].length - 1;
            candidates.push(str.slice(0, -len) + "e" + len);
        } else if (match = /^(\d)\.(\d+)e(-?\d+)$/.exec(str)) {
            candidates.push(match[1] + match[2] + "e" + (match[3] - match[2].length));
@@ -1842,11 +1878,12 @@ function OutputStream(options) {
    }

    function make_block(stmt, output) {
-        if (!stmt || stmt instanceof AST_EmptyStatement)
-            output.print("{}");
-        else if (stmt instanceof AST_BlockStatement)
+        output.space();
+        if (stmt instanceof AST_EmptyStatement) {
+            print_braced_empty(stmt, output);
+        } else if (stmt instanceof AST_BlockStatement) {
            stmt.print(output);
-        else output.with_block(function() {
+        } else output.with_block(function() {
            output.indent();
            stmt.print(output);
            output.newline();
@@ -1893,7 +1930,11 @@ function OutputStream(options) {
        output.add_mapping(this.start);
    });

-    DEFMAP([ AST_DestructuredKeyVal, AST_ObjectProperty ], function(output) {
+    DEFMAP([
+        AST_ClassProperty,
+        AST_DestructuredKeyVal,
+        AST_ObjectProperty,
+    ], function(output) {
        if (typeof this.key == "string") output.add_mapping(this.start, this.key);
    });
 })();
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -44,10 +44,10 @@

 "use strict";

-var KEYWORDS = "break case catch class const continue debugger default delete do else extends finally for function if in instanceof let new return switch throw try typeof var void while with";
+var KEYWORDS = "break case catch class const continue debugger default delete do else extends finally for function if in instanceof new return switch throw try typeof var void while with";
 var KEYWORDS_ATOM = "false null true";
 var RESERVED_WORDS = [
-    "abstract async await boolean byte char double enum export final float goto implements import int interface long native package private protected public short static super synchronized this throws transient volatile yield",
+    "abstract async await boolean byte char double enum export final float goto implements import int interface let long native package private protected public short static super synchronized this throws transient volatile yield",
    KEYWORDS_ATOM,
    KEYWORDS,
 ].join(" ");
@@ -104,12 +104,15 @@ var OPERATORS = makePredicate([
    ">>=",
    "<<=",
    ">>>=",
+    "&=",
    "|=",
    "^=",
-    "&=",
    "&&",
    "||",
    "??",
+    "&&=",
+    "||=",
+    "??=",
 ]);

 var NEWLINE_CHARS = "\n\r\u2028\u2029";
@@ -121,7 +124,7 @@ var PUNC_AFTER_EXPRESSION = PUNC_SEPARATORS + PUNC_CLOSERS;
 var PUNC_BEFORE_EXPRESSION = PUNC_OPENERS + PUNC_SEPARATORS;
 var PUNC_CHARS = PUNC_BEFORE_EXPRESSION + "`" + PUNC_CLOSERS;
 var WHITESPACE_CHARS = NEWLINE_CHARS + " \u00a0\t\f\u000b\u200b\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u202f\u205f\u3000\uFEFF";
-var NON_IDENTIFIER_CHARS = makePredicate(characters("./'\"" + OPERATOR_CHARS + PUNC_CHARS + WHITESPACE_CHARS));
+var NON_IDENTIFIER_CHARS = makePredicate(characters("./'\"#" + OPERATOR_CHARS + PUNC_CHARS + WHITESPACE_CHARS));

 NEWLINE_CHARS = makePredicate(characters(NEWLINE_CHARS));
 OPERATOR_CHARS = makePredicate(characters(OPERATOR_CHARS));
@@ -239,10 +242,10 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
        read_template   : with_eof_error("Unterminated template literal", function(strings) {
            var s = "";
            for (;;) {
-                var ch = next(true, true);
+                var ch = read();
                switch (ch) {
                  case "\\":
-                    ch += next(true, true);
+                    ch += read();
                    break;
                  case "`":
                    strings.push(s);
@@ -257,6 +260,11 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
                }
                s += ch;
            }
+
+            function read() {
+                var ch = next(true, true);
+                return ch == "\r" ? "\n" : ch;
+            }
        }),
    };
    var prev_was_dot = false;
@@ -348,7 +356,7 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {

    function read_while(pred) {
        var ret = "", ch;
-        while ((ch = peek()) && pred(ch)) ret += next();
+        while ((ch = peek()) && pred(ch, ret)) ret += next();
        return ret;
    }

@@ -356,24 +364,27 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
        js_error(err, filename, S.tokline, S.tokcol, S.tokpos);
    }

+    function is_octal(num) {
+        return /^0[0-7_]+$/.test(num);
+    }
+
    function read_num(prefix) {
        var has_e = false, after_e = false, has_x = false, has_dot = prefix == ".";
-        var num = read_while(function(ch) {
-            var code = ch.charCodeAt(0);
-            switch (code) {
-              case 120: case 88: // xX
+        var num = read_while(function(ch, str) {
+            switch (ch) {
+              case "x": case "X":
                return has_x ? false : (has_x = true);
-              case 101: case 69: // eE
+              case "e": case "E":
                return has_x ? true : has_e ? false : (has_e = after_e = true);
-              case 43: case 45: // +-
+              case "+": case "-":
                return after_e;
-              case (after_e = false, 46): // .
-                return (!has_dot && !has_x && !has_e) ? (has_dot = true) : false;
+              case (after_e = false, "."):
+                return has_dot || has_e || has_x || is_octal(str) ? false : (has_dot = true);
            }
-            return is_digit(code) || /[_0-9a-fo]/i.test(ch);
+            return /[_0-9a-dfo]/i.test(ch);
        });
        if (prefix) num = prefix + num;
-        if (/^0[0-7_]+$/.test(num)) {
+        if (is_octal(num)) {
            if (next_token.has_directive("use strict")) parse_error("Legacy octal literals are not allowed in strict mode");
        } else {
            num = num.replace(has_x ? /([1-9a-f]|.0)_(?=[0-9a-f])/gi : /([1-9]|.0)_(?=[0-9])/gi, "$1");
@@ -462,7 +473,7 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
    });

    function read_name() {
-        var backslash = false, name = "", ch, escaped = false, hex;
+        var backslash = false, ch, escaped = false, name = peek() == "#" ? next() : "";
        while (ch = peek()) {
            if (!backslash) {
                if (ch == "\\") escaped = backslash = true, next();
@@ -477,7 +488,7 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
            }
        }
        if (KEYWORDS[name] && escaped) {
-            hex = name.charCodeAt(0).toString(16).toUpperCase();
+            var hex = name.charCodeAt(0).toString(16).toUpperCase();
            name = "\\u" + "0000".substr(hex.length) + hex + name.slice(1);
        }
        return name;
@@ -612,7 +623,7 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
            if (PUNC_CHARS[ch]) return token("punc", next());
            if (looking_at("=>")) return token("punc", next() + next());
            if (OPERATOR_CHARS[ch]) return read_operator();
-            if (code == 92 || !NON_IDENTIFIER_CHARS[ch]) return read_word();
+            if (code == 35 || code == 92 || !NON_IDENTIFIER_CHARS[ch]) return read_word();
            break;
        }
        parse_error("Unexpected character '" + ch + "'");
@@ -653,7 +664,7 @@ var UNARY_PREFIX = makePredicate("typeof void delete -- ++ ! ~ - +");

 var UNARY_POSTFIX = makePredicate("-- ++");

-var ASSIGNMENT = makePredicate("= += -= /= *= %= **= >>= <<= >>>= |= ^= &=");
+var ASSIGNMENT = makePredicate("= += -= /= *= %= **= >>= <<= >>>= &= |= ^= &&= ||= ??=");

 var PRECEDENCE = function(a, ret) {
    for (var i = 0; i < a.length;) {
@@ -851,10 +862,20 @@ function parse($TEXT, options) {
                next();
                return export_();
              case "import":
-                if (!is_token(peek(), "punc", "(")) {
+                var token = peek();
+                if (!(token.type == "punc" && /^[(.]$/.test(token.value))) {
                    next();
                    return import_();
                }
+                break;
+              case "let":
+                if (is_vardefs()) {
+                    next();
+                    var node = let_();
+                    semicolon();
+                    return node;
+                }
+                break;
              case "yield":
                if (S.in_generator) return simple_statement();
                break;
@@ -940,12 +961,6 @@ function parse($TEXT, options) {
                next();
                return if_();

-              case "let":
-                next();
-                var node = let_();
-                semicolon();
-                return node;
-
              case "return":
                if (S.in_function == 0 && !options.bare_returns)
                    croak("'return' outside of function");
@@ -1182,10 +1197,10 @@ function parse($TEXT, options) {
        var await = is("name", "await") && next();
        expect("(");
        var init = null;
-        if (!is("punc", ";")) {
+        if (await || !is("punc", ";")) {
            init = is("keyword", "const")
                ? (next(), const_(true))
-                : is("keyword", "let")
+                : is("name", "let") && is_vardefs()
                ? (next(), let_(true))
                : is("keyword", "var")
                ? (next(), var_(true))
@@ -1233,6 +1248,7 @@ function parse($TEXT, options) {
    }

    function for_enum(ctor, init) {
+        handle_regexp();
        var obj = expression();
        expect(")");
        return new ctor({
@@ -1300,6 +1316,11 @@ function parse($TEXT, options) {
        }
        if (node instanceof AST_SymbolFunarg) return node;
        if (node instanceof AST_SymbolRef) return new AST_SymbolFunarg(node);
+        if (node instanceof AST_Yield) return new AST_SymbolFunarg({
+            start: node.start,
+            name: "yield",
+            end: node.end,
+        });
        token_error(node.start, "Invalid arrow parameter");
    }

@@ -1326,21 +1347,19 @@ function parse($TEXT, options) {
        if (is("punc", "{")) {
            body = block_();
            value = null;
-            if (S.input.has_directive("use strict")) {
-                argnames.forEach(strict_verify_symbol);
-            }
        } else {
            body = [];
            handle_regexp();
            value = maybe_assign();
        }
+        var is_strict = S.input.has_directive("use strict");
        S.input.pop_directives_stack();
        --S.in_function;
        S.in_loop = loop;
        S.labels = labels;
        S.in_generator = was_gen;
        S.in_async = was_async;
-        return new (async ? AST_AsyncArrow : AST_Arrow)({
+        var node = new (async ? AST_AsyncArrow : AST_Arrow)({
            start: start,
            argnames: argnames,
            rest: rest,
@@ -1348,6 +1367,8 @@ function parse($TEXT, options) {
            value: value,
            end: prev(),
        });
+        if (is_strict) node.each_argname(strict_verify_symbol);
+        return node;
    }

    var function_ = function(ctor) {
@@ -1380,23 +1401,24 @@ function parse($TEXT, options) {
        S.in_loop = 0;
        S.labels = [];
        var body = block_();
-        if (S.input.has_directive("use strict")) {
-            if (name) strict_verify_symbol(name);
-            argnames.forEach(strict_verify_symbol);
-            if (argnames.rest) strict_verify_symbol(argnames.rest);
-        }
+        var is_strict = S.input.has_directive("use strict");
        S.input.pop_directives_stack();
        --S.in_function;
        S.in_loop = loop;
        S.labels = labels;
        S.in_generator = was_gen;
        S.in_async = was_async;
-        return new ctor({
+        var node = new ctor({
            name: name,
            argnames: argnames,
            rest: argnames.rest || null,
            body: body
        });
+        if (is_strict) {
+            if (name) strict_verify_symbol(name);
+            node.each_argname(strict_verify_symbol);
+        }
+        return node;
    };

    function if_() {
@@ -1488,6 +1510,7 @@ function parse($TEXT, options) {
                body.start = start;
                body.end = prev();
            } else {
+                handle_regexp();
                body = expression();
                semicolon();
            }
@@ -1525,12 +1548,18 @@ function parse($TEXT, options) {
    }

    var export_decl = embed_tokens(function() {
-        if (is("name", "async")) {
+        if (is("name")) switch (S.token.value) {
+          case "async":
            next();
            expect_token("keyword", "function");
            if (!is("operator", "*")) return function_(AST_AsyncDefun);
            next();
            return function_(AST_AsyncGeneratorDefun);
+          case "let":
+            next();
+            var node = let_();
+            semicolon();
+            return node;
        } else if (is("keyword")) switch (S.token.value) {
          case "class":
            next();
@@ -1545,11 +1574,6 @@ function parse($TEXT, options) {
            if (!is("operator", "*")) return function_(AST_Defun);
            next();
            return function_(AST_GeneratorDefun);
-          case "let":
-            next();
-            var node = let_();
-            semicolon();
-            return node;
          case "var":
            next();
            var node = var_();
@@ -1710,6 +1734,11 @@ function parse($TEXT, options) {
        return a;
    }

+    function is_vardefs() {
+        var token = peek();
+        return is_token(token, "name") || is_token(token, "punc", "[") || is_token(token, "punc", "{");
+    }
+
    var const_ = function(no_in) {
        return new AST_Const({
            start       : prev(),
@@ -1808,10 +1837,7 @@ function parse($TEXT, options) {
        if (is("punc")) {
            switch (start.value) {
              case "`":
-                var tmpl = template(null);
-                tmpl.start = start;
-                tmpl.end = prev();
-                return subscripts(tmpl, allow_calls);
+                return subscripts(template(null), allow_calls);
              case "(":
                next();
                if (is("punc", ")")) {
@@ -2123,7 +2149,7 @@ function parse($TEXT, options) {
    }

    function strict_verify_symbol(sym) {
-        if (sym.name == "arguments" || sym.name == "eval")
+        if (sym.name == "arguments" || sym.name == "eval" || sym.name == "let")
            token_error(sym.start, "Unexpected " + sym.name + " in strict mode");
    }

@@ -2220,6 +2246,7 @@ function parse($TEXT, options) {
    }

    function template(tag) {
+        var start = tag ? tag.start : S.token;
        var read = S.input.context().read_template;
        var strings = [];
        var expressions = [];
@@ -2230,64 +2257,73 @@ function parse($TEXT, options) {
        }
        next();
        return new AST_Template({
+            start: start,
            expressions: expressions,
            strings: strings,
            tag: tag,
+            end: prev(),
        });
    }

-    var subscripts = function(expr, allow_calls) {
+    function subscripts(expr, allow_calls) {
        var start = expr.start;
-        if (is("punc", ".")) {
-            next();
-            return subscripts(new AST_Dot({
-                start      : start,
-                expression : expr,
-                property   : as_name(),
-                end        : prev()
-            }), allow_calls);
-        }
-        if (is("punc", "[")) {
-            next();
-            var prop = expression();
-            expect("]");
-            return subscripts(new AST_Sub({
-                start      : start,
-                expression : expr,
-                property   : prop,
-                end        : prev()
-            }), allow_calls);
-        }
-        if (allow_calls && is("punc", "(")) {
-            next();
-            var call = new AST_Call({
-                start      : start,
-                expression : expr,
-                args       : expr_list(")", !options.strict),
-                end        : prev()
-            });
-            return subscripts(call, true);
-        }
-        if (is("punc", "`")) {
-            var tmpl = template(expr);
-            tmpl.start = expr.start;
-            tmpl.end = prev();
-            return subscripts(tmpl, allow_calls);
+        var optional = null;
+        while (true) {
+            if (is("operator", "?") && is_token(peek(), "punc", ".")) {
+                next();
+                next();
+                optional = expr;
+            }
+            if (is("punc", "[")) {
+                next();
+                var prop = expression();
+                expect("]");
+                expr = new AST_Sub({
+                    start: start,
+                    optional: optional === expr,
+                    expression: expr,
+                    property: prop,
+                    end: prev(),
+                });
+            } else if (allow_calls && is("punc", "(")) {
+                next();
+                expr = new AST_Call({
+                    start: start,
+                    optional: optional === expr,
+                    expression: expr,
+                    args: expr_list(")", !options.strict),
+                    end: prev(),
+                });
+            } else if (optional === expr || is("punc", ".")) {
+                if (optional !== expr) next();
+                expr = new AST_Dot({
+                    start: start,
+                    optional: optional === expr,
+                    expression: expr,
+                    property: as_name(),
+                    end: prev(),
+                });
+            } else if (is("punc", "`")) {
+                if (optional) croak("Invalid template on optional chain");
+                expr = template(expr);
+            } else {
+                break;
+            }
        }
+        if (optional) expr.terminal = true;
        if (expr instanceof AST_Call && !expr.pure) {
            var start = expr.start;
            var comments = start.comments_before;
            var i = HOP(start, "comments_before_length") ? start.comments_before_length : comments.length;
            while (--i >= 0) {
-                var match = /[@#]__PURE__/.exec(comments[i].value);
-                if (match) {
-                    expr.pure = match[0];
+                if (/[@#]__PURE__/.test(comments[i].value)) {
+                    expr.pure = true;
                    break;
                }
            }
        }
        return expr;
-    };
+    }

    function maybe_unary(no_in) {
        var start = S.token;
@@ -2396,7 +2432,7 @@ function parse($TEXT, options) {
    };

    function is_assignable(expr) {
-        return expr instanceof AST_PropAccess || expr instanceof AST_SymbolRef;
+        return expr instanceof AST_PropAccess && !expr.optional || expr instanceof AST_SymbolRef;
    }

    function to_destructured(node) {
@@ -2518,7 +2554,7 @@ function parse($TEXT, options) {
        while (!is("eof"))
            body.push(statement());
        S.input.pop_directives_stack();
-        var end = prev();
+        var end = prev() || start;
        var toplevel = options.toplevel;
        if (toplevel) {
            toplevel.body = toplevel.body.concat(body);
--- a/lib/propmangle.js
+++ b/lib/propmangle.js
@@ -44,7 +44,7 @@
 "use strict";

 var builtins = function() {
-    var names = [];
+    var names = new Dictionary();
    // NaN will be included due to Number.NaN
    [
        "null",
@@ -72,16 +72,18 @@ var builtins = function() {
            Object.getOwnPropertyNames(ctor.prototype).map(add);
        }
    });
-    return makePredicate(names);
+    return names;

    function add(name) {
-        names.push(name);
+        names.set(name, true);
    }
 }();

 function reserve_quoted_keys(ast, reserved) {
    ast.walk(new TreeWalker(function(node) {
-        if (node instanceof AST_ObjectProperty) {
+        if (node instanceof AST_ClassProperty) {
+            if (node.start && node.start.quote) add(node.key);
+        } else if (node instanceof AST_ObjectProperty) {
            if (node.start && node.start.quote) add(node.key);
        } else if (node instanceof AST_Sub) {
            addStrings(node.property, add);
@@ -114,9 +116,9 @@ function mangle_properties(ast, options) {
        reserved: null,
    }, true);

-    var reserved = Object.create(options.builtins ? null : builtins);
+    var reserved = options.builtins ? new Dictionary() : builtins.clone();
    if (Array.isArray(options.reserved)) options.reserved.forEach(function(name) {
-        reserved[name] = true;
+        reserved.set(name, true);
    });

    var cname = -1;
@@ -124,7 +126,7 @@ function mangle_properties(ast, options) {
    if (options.cache) {
        cache = options.cache.props;
        cache.each(function(name) {
-            reserved[name] = true;
+            reserved.set(name, true);
        });
    } else {
        cache = new Dictionary();
@@ -139,8 +141,8 @@ function mangle_properties(ast, options) {
    var debug_suffix;
    if (debug) debug_suffix = options.debug === true ? "" : options.debug;

-    var names_to_mangle = Object.create(null);
-    var unmangleable = Object.create(reserved);
+    var names_to_mangle = new Dictionary();
+    var unmangleable = reserved.clone();

    // step 1: find candidates to mangle
    ast.walk(new TreeWalker(function(node) {
@@ -163,6 +165,8 @@ function mangle_properties(ast, options) {
                addStrings(node.args[0], add);
                break;
            }
+        } else if (node instanceof AST_ClassProperty) {
+            if (typeof node.key == "string") add(node.key);
        } else if (node instanceof AST_Dot) {
            add(node.property);
        } else if (node instanceof AST_ObjectProperty) {
@@ -193,6 +197,8 @@ function mangle_properties(ast, options) {
                mangleStrings(node.args[0]);
                break;
            }
+        } else if (node instanceof AST_ClassProperty) {
+            if (typeof node.key == "string") node.key = mangle(node.key);
        } else if (node instanceof AST_Dot) {
            node.property = mangle(node.property);
        } else if (node instanceof AST_ObjectProperty) {
@@ -205,26 +211,24 @@ function mangle_properties(ast, options) {
    // only function declarations after this line

    function can_mangle(name) {
-        if (unmangleable[name]) return false;
+        if (unmangleable.has(name)) return false;
        if (/^-?[0-9]+(\.[0-9]+)?(e[+-][0-9]+)?$/.test(name)) return false;
        return true;
    }

    function should_mangle(name) {
-        if (reserved[name]) return false;
+        if (reserved.has(name)) return false;
        if (regex && !regex.test(name)) return false;
-        return cache.has(name) || names_to_mangle[name];
+        return cache.has(name) || names_to_mangle.has(name);
    }

    function add(name) {
-        if (can_mangle(name)) names_to_mangle[name] = true;
-        if (!should_mangle(name)) unmangleable[name] = true;
+        if (can_mangle(name)) names_to_mangle.set(name, true);
+        if (!should_mangle(name)) unmangleable.set(name, true);
    }

    function mangle(name) {
-        if (!should_mangle(name)) {
-            return name;
-        }
+        if (!should_mangle(name)) return name;
        var mangled = cache.get(name);
        if (!mangled) {
            if (debug) {
@@ -236,6 +240,7 @@ function mangle_properties(ast, options) {
            if (!mangled) do {
                mangled = base54(++cname);
            } while (!can_mangle(mangled));
+            if (/^#/.test(name)) mangled = "#" + mangled;
            cache.set(name, mangled);
        }
        return mangled;
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -44,9 +44,9 @@
 "use strict";

 function SymbolDef(id, scope, orig, init) {
+    this._bits = 0;
+    this.defun = undefined;
    this.eliminated = 0;
-    this.exported = false;
-    this.global = false;
    this.id = id;
    this.init = init;
    this.mangled_name = null;
@@ -54,8 +54,8 @@ function SymbolDef(id, scope, orig, init) {
    this.orig = [ orig ];
    this.references = [];
    this.replaced = 0;
+    this.safe_ids = undefined;
    this.scope = scope;
-    this.undeclared = false;
 }

 SymbolDef.prototype = {
@@ -80,29 +80,47 @@ SymbolDef.prototype = {
        }
    },
    redefined: function() {
-        var scope = this.defun;
+        var self = this;
+        var scope = self.defun;
        if (!scope) return;
-        var name = this.name;
+        var name = self.name;
        var def = scope.variables.get(name)
            || scope instanceof AST_Toplevel && scope.globals.get(name)
-            || this.orig[0] instanceof AST_SymbolConst && find_if(function(def) {
+            || self.orig[0] instanceof AST_SymbolConst && find_if(function(def) {
                return def.name == name;
            }, scope.enclosed);
-        if (def && def !== this) return def.redefined() || def;
+        if (def && def !== self) return def.redefined() || def;
    },
    unmangleable: function(options) {
-        return this.global && !options.toplevel
-            || this.exported
-            || this.undeclared
-            || !options.eval && this.scope.pinned()
-            || options.keep_fnames
-                && (this.orig[0] instanceof AST_SymbolClass
-                    || this.orig[0] instanceof AST_SymbolDefClass
-                    || this.orig[0] instanceof AST_SymbolDefun
-                    || this.orig[0] instanceof AST_SymbolLambda);
+        if (this.exported) return true;
+        if (this.undeclared) return true;
+        if (!options.eval && this.scope.pinned()) return true;
+        if (options.keep_fargs && is_funarg(this)) return true;
+        if (options.keep_fnames) {
+            var sym = this.orig[0];
+            if (sym instanceof AST_SymbolClass) return true;
+            if (sym instanceof AST_SymbolDefClass) return true;
+            if (sym instanceof AST_SymbolDefun) return true;
+            if (sym instanceof AST_SymbolLambda) return true;
+        }
+        if (!options.toplevel && this.global) return true;
+        return false;
    },
 };

+DEF_BITPROPS(SymbolDef, [
+    "const_redefs",
+    "cross_loop",
+    "direct_access",
+    "exported",
+    "global",
+    "undeclared",
+]);
+
+function is_funarg(def) {
+    return def.orig[0] instanceof AST_SymbolFunarg || def.orig[1] instanceof AST_SymbolFunarg;
+}
+
 var unary_side_effects = makePredicate("delete ++ --");

 function is_lhs(node, parent) {
@@ -117,7 +135,7 @@ function is_lhs(node, parent) {
 AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
    options = defaults(options, {
        cache: null,
-        ie8: false,
+        ie: false,
    });

    // pass 1: setup scope chaining and handle definitions
@@ -204,20 +222,17 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
        } else if (node instanceof AST_SymbolDefun) {
            var def = defun.def_function(node, tw.parent());
            if (exported) def.exported = true;
-            entangle(defun, scope);
        } else if (node instanceof AST_SymbolFunarg) {
            defun.def_variable(node);
-            entangle(defun, scope);
        } else if (node instanceof AST_SymbolLambda) {
            var def = defun.def_function(node, node.name == "arguments" ? undefined : defun);
-            if (options.ie8) def.defun = defun.parent_scope.resolve();
+            if (options.ie) def.defun = defun.parent_scope.resolve();
        } else if (node instanceof AST_SymbolLet) {
            var def = scope.def_variable(node);
            if (exported) def.exported = true;
        } else if (node instanceof AST_SymbolVar) {
            var def = defun.def_variable(node, node instanceof AST_SymbolImport ? undefined : null);
            if (exported) def.exported = true;
-            entangle(defun, scope);
        }

        function walk_scope(descend) {
@@ -230,16 +245,6 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
            scope = save_scope;
            defun = save_defun;
        }
-
-        function entangle(defun, scope) {
-            if (defun === scope) return;
-            node.mark_enclosed(options);
-            var def = scope.find_variable(node.name);
-            if (node.thedef === def) return;
-            node.thedef = def;
-            def.orig.push(node);
-            node.mark_enclosed(options);
-        }
    });
    self.make_def = function(orig, init) {
        return new SymbolDef(++next_def_id, this, orig, init);
@@ -260,6 +265,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
        }
        if (node instanceof AST_Lambda) {
            in_arg.push(node);
+            if (node.name) node.name.walk(tw);
            node.argnames.forEach(function(argname) {
                argname.walk(tw);
            });
@@ -273,17 +279,29 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
            return true;
        }
        if (node instanceof AST_SymbolDeclaration) {
+            var def = node.definition();
+            def.preinit = def.references.length;
            if (node instanceof AST_SymbolCatch) {
                // ensure mangling works if `catch` reuses a scope variable
-                var def = node.definition().redefined();
-                if (def) for (var s = node.scope; s; s = s.parent_scope) {
-                    push_uniq(s.enclosed, def);
-                    if (s === def.scope) break;
+                var redef = def.redefined();
+                if (redef) for (var s = node.scope; s; s = s.parent_scope) {
+                    push_uniq(s.enclosed, redef);
+                    if (s === redef.scope) break;
                }
            } else if (node instanceof AST_SymbolConst) {
                // ensure compression works if `const` reuses a scope variable
-                var redef = node.definition().redefined();
+                var redef = def.redefined();
                if (redef) redef.const_redefs = true;
+            } else if (def.scope !== node.scope && (node instanceof AST_SymbolDefun
+                || node instanceof AST_SymbolFunarg
+                || node instanceof AST_SymbolVar)) {
+                node.mark_enclosed(options);
+                var redef = node.scope.find_variable(node.name);
+                if (node.thedef !== redef) {
+                    node.thedef = redef;
+                    redef.orig.push(node);
+                    node.mark_enclosed(options);
+                }
            }
            if (node.name != "arguments") return true;
            var parent = node instanceof AST_SymbolVar && tw.parent();
@@ -348,7 +366,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
    self.walk(tw);

    // pass 3: fix up any scoping issue with IE8
-    if (options.ie8) self.walk(new TreeWalker(function(node) {
+    if (options.ie) self.walk(new TreeWalker(function(node) {
        if (node instanceof AST_SymbolCatch) {
            var scope = node.thedef.defun;
            if (scope.name instanceof AST_SymbolLambda && scope.name.name == node.name) {
@@ -360,7 +378,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
        if (node instanceof AST_SymbolLambda) {
            var def = node.thedef;
            if (!redefine(node, node.scope.parent_scope.resolve())) {
-                delete def.defun;
+                def.defun = undefined;
            } else if (typeof node.thedef.init !== "undefined") {
                node.thedef.init = false;
            } else if (def.init) {
@@ -394,13 +412,14 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
        } else {
            new_def = scope.def_variable(node);
        }
+        if (new_def.undeclared) self.variables.set(name, new_def);
+        if (name == "arguments" && is_arguments(old_def) && node instanceof AST_SymbolLambda) return true;
        old_def.defun = new_def.scope;
        old_def.forEach(function(node) {
            node.redef = old_def;
            node.thedef = new_def;
            node.reference(options);
        });
-        if (new_def.undeclared) self.variables.set(name, new_def);
        return true;
    }
 });
@@ -461,9 +480,12 @@ AST_Symbol.DEFMETHOD("mark_enclosed", function(options) {
    for (var s = this.scope; s; s = s.parent_scope) {
        push_uniq(s.enclosed, def);
        if (!options) {
-            delete s._var_names;
-        } else if (options.keep_fnames) {
-            s.functions.each(function(d) {
+            s._var_names = undefined;
+        } else {
+            if (options.keep_fargs && s instanceof AST_Lambda) s.each_argname(function(arg) {
+                push_uniq(def.scope.enclosed, arg.definition());
+            });
+            if (options.keep_fnames) s.functions.each(function(d) {
                push_uniq(def.scope.enclosed, d);
            });
        }
@@ -506,12 +528,12 @@ function names_in_use(scope, options) {
    if (!names) {
        scope.cname = -1;
        scope.cname_holes = [];
-        scope.names_in_use = names = Object.create(null);
+        scope.names_in_use = names = new Dictionary();
        var cache = options.cache && options.cache.props;
        scope.enclosed.forEach(function(def) {
-            if (def.unmangleable(options)) names[def.name] = true;
+            if (def.unmangleable(options)) names.set(def.name, true);
            if (def.global && cache && cache.has(def.name)) {
-                names[cache.get(def.name)] = true;
+                names.set(cache.get(def.name), true);
            }
        });
    }
@@ -522,34 +544,33 @@ function next_mangled_name(def, options) {
    var scope = def.scope;
    var in_use = names_in_use(scope, options);
    var holes = scope.cname_holes;
-    var names = Object.create(null);
+    var names = new Dictionary();
    var scopes = [ scope ];
    def.forEach(function(sym) {
        var scope = sym.scope;
        do {
-            if (scopes.indexOf(scope) < 0) {
-                for (var name in names_in_use(scope, options)) {
-                    names[name] = true;
-                }
-                scopes.push(scope);
-            } else break;
+            if (member(scope, scopes)) break;
+            names_in_use(scope, options).each(function(marker, name) {
+                names.set(name, marker);
+            });
+            scopes.push(scope);
        } while (scope = scope.parent_scope);
    });
    var name;
    for (var i = 0; i < holes.length; i++) {
        name = base54(holes[i]);
-        if (names[name]) continue;
+        if (names.has(name)) continue;
        holes.splice(i, 1);
-        in_use[name] = true;
+        in_use.set(name, true);
        return name;
    }
    while (true) {
        name = base54(++scope.cname);
-        if (in_use[name] || RESERVED_WORDS[name] || options.reserved.has[name]) continue;
-        if (!names[name]) break;
+        if (in_use.has(name) || RESERVED_WORDS[name] || options.reserved.has[name]) continue;
+        if (!names.has(name)) break;
        holes.push(scope.cname);
    }
-    in_use[name] = true;
+    in_use.set(name, true);
    return name;
 }

@@ -568,7 +589,8 @@ AST_Symbol.DEFMETHOD("definition", function() {
 function _default_mangler_options(options) {
    options = defaults(options, {
        eval        : false,
-        ie8         : false,
+        ie          : false,
+        keep_fargs  : false,
        keep_fnames : false,
        reserved    : [],
        toplevel    : false,
@@ -576,32 +598,30 @@ function _default_mangler_options(options) {
        webkit      : false,
    });
    if (!Array.isArray(options.reserved)) options.reserved = [];
-    // Never mangle arguments
+    // Never mangle `arguments`
    push_uniq(options.reserved, "arguments");
    options.reserved.has = makePredicate(options.reserved);
    return options;
 }

+// We only need to mangle declaration nodes. Special logic wired into the code
+// generator will display the mangled name if it is present (and for
+// `AST_SymbolRef`s it will use the mangled name of the `AST_SymbolDeclaration`
+// that it points to).
 AST_Toplevel.DEFMETHOD("mangle_names", function(options) {
    options = _default_mangler_options(options);
-
-    // We only need to mangle declaration nodes.  Special logic wired
-    // into the code generator will display the mangled name if it's
-    // present (and for AST_SymbolRef-s it'll use the mangled name of
-    // the AST_SymbolDeclaration that it points to).
-    var lname = -1;
-
    if (options.cache && options.cache.props) {
        var mangled_names = names_in_use(this, options);
        options.cache.props.each(function(mangled_name) {
-            mangled_names[mangled_name] = true;
+            mangled_names.set(mangled_name, true);
        });
    }
-
+    var cutoff = 10;
+    var lname = -1;
    var redefined = [];
    var tw = new TreeWalker(function(node, descend) {
        if (node instanceof AST_LabeledStatement) {
-            // lname is incremented when we get to the AST_Label
+            // `lname` is incremented when we get to the `AST_Label`
            var save_nesting = lname;
            descend();
            if (!options.v8 || !in_label(tw)) lname = save_nesting;
@@ -623,9 +643,9 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options) {
                    });
                }, true);
            }
-            node.to_mangle = [];
+            var to_mangle = node.to_mangle = [];
            node.variables.each(function(def) {
-                if (!defer_redef(def)) node.to_mangle.push(def);
+                if (!defer_redef(def)) to_mangle.push(def);
            });
            descend();
            if (options.cache && node instanceof AST_Toplevel) {
@@ -636,7 +656,23 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options) {
                sym.scope = node;
                sym.reference(options);
            }
-            node.to_mangle.forEach(mangle);
+            if (to_mangle.length > cutoff) {
+                var indices = to_mangle.map(function(def, index) {
+                    return index;
+                }).sort(function(i, j) {
+                    return to_mangle[j].references.length - to_mangle[i].references.length || i - j;
+                });
+                to_mangle = indices.slice(0, cutoff).sort(function(i, j) {
+                    return i - j;
+                }).map(function(index) {
+                    return to_mangle[index];
+                }).concat(indices.slice(cutoff).sort(function(i, j) {
+                    return i - j;
+                }).map(function(index) {
+                    return to_mangle[index];
+                }));
+            }
+            to_mangle.forEach(mangle);
            return true;
        }
        if (node instanceof AST_Label) {
@@ -798,6 +834,7 @@ var base54 = (function() {
    var leading = init("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$_");
    var chars, frequency;
    function reset() {
+        chars = null;
        frequency = Object.create(freq);
    }
    base54.consider = function(str, delta) {
@@ -809,19 +846,15 @@ var base54 = (function() {
        return frequency[b] - frequency[a];
    }
    base54.sort = function() {
-        chars = leading.sort(compare).concat(digits.sort(compare));
+        chars = leading.sort(compare).concat(digits).sort(compare);
    };
    base54.reset = reset;
    reset();
    function base54(num) {
-        var ret = "", base = 54;
-        num++;
-        do {
-            num--;
-            ret += chars[num % base];
-            num = Math.floor(num / base);
-            base = 64;
-        } while (num > 0);
+        var ret = leading[num % 54];
+        for (num = Math.floor(num / 54); --num >= 0; num >>= 6) {
+            ret += chars[num & 0x3F];
+        }
        return ret;
    }
    return base54;
--- a/lib/sourcemap.js
+++ b/lib/sourcemap.js
@@ -77,21 +77,23 @@ function vlq_encode(num) {
 }

 function create_array_map() {
-    var map = Object.create(null);
+    var map = new Dictionary();
    var array = [];
    array.index = function(name) {
-        if (!HOP(map, name)) {
-            map[name] = array.length;
+        var index = map.get(name);
+        if (!(index >= 0)) {
+            index = array.length;
            array.push(name);
+            map.set(name, index);
        }
-        return map[name];
+        return index;
    };
    return array;
 }

 function SourceMap(options) {
    var sources = create_array_map();
-    var sources_content = options.includeSources && Object.create(null);
+    var sources_content = options.includeSources && new Dictionary();
    var names = create_array_map();
    var mappings = "";
    if (options.orig) Object.keys(options.orig).forEach(function(name) {
@@ -110,7 +112,7 @@ function SourceMap(options) {
        if (!sources_content || !map.sourcesContent) return;
        for (var i = 0; i < map.sources.length; i++) {
            var content = map.sourcesContent[i];
-            if (content) sources_content[map.sources[i]] = content;
+            if (content) sources_content.set(map.sources[i], content);
        }
    });
    var prev_source;
@@ -144,8 +146,8 @@ function SourceMap(options) {
            add(source, gen_line, gen_col, orig_line, orig_col, name);
        } : add,
        setSourceContent: sources_content ? function(source, content) {
-            if (!(source in sources_content)) {
-                sources_content[source] = content;
+            if (!sources_content.has(source)) {
+                sources_content.set(source, content);
            }
        } : noop,
        toString: function() {
@@ -155,7 +157,7 @@ function SourceMap(options) {
                sourceRoot: options.root || undefined,
                sources: sources,
                sourcesContent: sources_content ? sources.map(function(source) {
-                    return sources_content[source] || null;
+                    return sources_content.get(source) || null;
                }) : undefined,
                names: names,
                mappings: mappings,
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -96,15 +96,6 @@ function defaults(args, defs, croak) {
    return defs;
 }

-function merge(obj, ext) {
-    var count = 0;
-    for (var i in ext) if (HOP(ext, i)) {
-        obj[i] = ext[i];
-        count++;
-    }
-    return count;
-}
-
 function noop() {}
 function return_false() { return false; }
 function return_true() { return true; }
@@ -143,7 +134,7 @@ function push_uniq(array, el) {
 }

 function string_template(text, props) {
-    return text.replace(/\{([^}]+)\}/g, function(str, p) {
+    return text.replace(/\{([^{}]+)\}/g, function(str, p) {
        var value = props[p];
        return value instanceof AST_Node ? value.print_to_string() : value;
    });
@@ -171,63 +162,80 @@ function all(array, predicate) {
 }

 function Dictionary() {
-    this._values = Object.create(null);
-    this._size = 0;
+    this.values = Object.create(null);
 }
 Dictionary.prototype = {
    set: function(key, val) {
-        if (!this.has(key)) ++this._size;
-        this._values["$" + key] = val;
+        if (key == "__proto__") {
+            this.proto_value = val;
+        } else {
+            this.values[key] = val;
+        }
        return this;
    },
    add: function(key, val) {
-        if (this.has(key)) {
-            this.get(key).push(val);
+        var list = this.get(key);
+        if (list) {
+            list.push(val);
        } else {
            this.set(key, [ val ]);
        }
        return this;
    },
-    get: function(key) { return this._values["$" + key] },
+    get: function(key) {
+        return key == "__proto__" ? this.proto_value : this.values[key];
+    },
    del: function(key) {
-        if (this.has(key)) {
-            --this._size;
-            delete this._values["$" + key];
+        if (key == "__proto__") {
+            delete this.proto_value;
+        } else {
+            delete this.values[key];
        }
        return this;
    },
-    has: function(key) { return ("$" + key) in this._values },
+    has: function(key) {
+        return key == "__proto__" ? "proto_value" in this : key in this.values;
+    },
    all: function(predicate) {
-        for (var i in this._values)
-            if (!predicate(this._values[i], i.substr(1)))
-                return false;
+        for (var i in this.values)
+            if (!predicate(this.values[i], i)) return false;
+        if ("proto_value" in this && !predicate(this.proto_value, "__proto__")) return false;
        return true;
    },
    each: function(f) {
-        for (var i in this._values)
-            f(this._values[i], i.substr(1));
+        for (var i in this.values)
+            f(this.values[i], i);
+        if ("proto_value" in this) f(this.proto_value, "__proto__");
    },
    size: function() {
-        return this._size;
+        return Object.keys(this.values).length + ("proto_value" in this);
    },
    map: function(f) {
        var ret = [];
-        for (var i in this._values)
-            ret.push(f(this._values[i], i.substr(1)));
+        for (var i in this.values)
+            ret.push(f(this.values[i], i));
+        if ("proto_value" in this) ret.push(f(this.proto_value, "__proto__"));
        return ret;
    },
    clone: function() {
        var ret = new Dictionary();
-        for (var i in this._values)
-            ret._values[i] = this._values[i];
-        ret._size = this._size;
+        this.each(function(value, i) {
+            ret.set(i, value);
+        });
        return ret;
    },
-    toObject: function() { return this._values }
+    toObject: function() {
+        var obj = {};
+        this.each(function(value, i) {
+            obj["$" + i] = value;
+        });
+        return obj;
+    },
 };
 Dictionary.fromObject = function(obj) {
    var dict = new Dictionary();
-    dict._size = merge(dict._values, obj);
+    for (var i in obj)
+        if (HOP(obj, i)) dict.set(i.slice(1), obj[i]);
    return dict;
 };

@@ -265,3 +273,21 @@ function first_in_statement(stack, arrow, export_default) {
        return false;
    }
 }
+
+function DEF_BITPROPS(ctor, props) {
+    if (props.length > 31) throw new Error("Too many properties: " + props.length + "\n" + props.join(", "));
+    props.forEach(function(name, pos) {
+        var mask = 1 << pos;
+        Object.defineProperty(ctor.prototype, name, {
+            get: function() {
+                return !!(this._bits & mask);
+            },
+            set: function(val) {
+                if (val)
+                    this._bits |= mask;
+                else
+                    this._bits &= ~mask;
+            },
+        });
+    });
+}
--- a/package.json
+++ b/package.json
@@ -3,7 +3,7 @@
  "description": "JavaScript parser, mangler/compressor and beautifier toolkit",
  "author": "Mihai Bazon <mihai.bazon@gmail.com> (http://lisperator.net/)",
  "license": "BSD-2-Clause",
-  "version": "3.13.2",
+  "version": "3.15.0",
  "engines": {
    "node": ">=0.8.0"
  },
@@ -23,7 +23,7 @@
    "LICENSE"
  ],
  "devDependencies": {
-    "acorn": "~7.1.0",
+    "acorn": "~8.2.1",
    "semver": "~6.3.0"
  },
  "scripts": {
--- a/test/benchmark.js
+++ b/test/benchmark.js
@@ -16,7 +16,7 @@ var urls = [
    "https://code.angularjs.org/1.7.8/angular.js",
    "https://unpkg.com/mathjs@6.2.3/dist/math.js",
    "https://unpkg.com/react@15.3.2/dist/react.js",
-    "https://cdnjs.cloudflare.com/ajax/libs/d3/5.12.0/d3.js",
+    "https://cdnjs.cloudflare.com/ajax/libs/d3/6.7.0/d3.js",
    "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.js",
    "https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js",
    "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.12.2/ember.prod.js",
--- a/test/compress/annotations.js
+++ b/test/compress/annotations.js
@@ -256,6 +256,7 @@ issue_3858: {
        collapse_vars: true,
        inline: true,
        keep_fargs: false,
+        unsafe: true,
        unused: true,
    }
    input: {
@@ -441,9 +442,9 @@ compress_annotations_disabled_output_annotations_enabled: {
    }
    expect_exact: [
        "/*@__PURE__*/a(3),",
-        "/*#__PURE__*/b(5),",
+        "/*@__PURE__*/b(5),",
        "c(side_effect),",
-        "/*#__PURE__*/d(effect());",
+        "/*@__PURE__*/d(effect());",
    ]
 }

--- a/test/compress/arguments.js
+++ b/test/compress/arguments.js
@@ -254,6 +254,25 @@ duplicate_argname: {
    expect_stdout: "bar 42 foo 42 bar"
 }

+fraction: {
+    options = {
+        arguments: true,
+        keep_fargs: false,
+        reduce_vars: true,
+    }
+    input: {
+        console.log(function() {
+            return arguments[0.3];
+        }("FAIL") || "PASS");
+    }
+    expect: {
+        console.log(function() {
+            return arguments[0.3];
+        }("FAIL") || "PASS");
+    }
+    expect_stdout: "PASS"
+}
+
 issue_3273: {
    options = {
        arguments: true,
--- a/test/compress/arrows.js
+++ b/test/compress/arrows.js
@@ -363,6 +363,28 @@ negate: {
 }

 inline_this: {
+    options = {
+        inline: true,
+    }
+    input: {
+        var p = "PASS";
+        console.log({
+            p: "FAIL",
+            q: (() => this.p)(),
+        }.q);
+    }
+    expect: {
+        var p = "PASS";
+        console.log({
+            p: "FAIL",
+            q: this.p,
+        }.q);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+dont_inline_this: {
    options = {
        inline: true,
    }
@@ -421,6 +443,7 @@ collapse_value: {
        arrows: true,
        collapse_vars: true,
        keep_fargs: false,
+        unsafe: true,
        unused: true,
    }
    input: {
@@ -485,7 +508,7 @@ drop_value: {
        ((a, b) => a + b)(console.log(42));
    }
    expect: {
-        ((a, b) => {})(console.log(42));
+        void console.log(42);
    }
    expect_stdout: "42"
    node_version: ">=4"
@@ -555,6 +578,75 @@ reduce_iife_3: {
    node_version: ">=4"
 }

+reduce_lambda_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var f = () => {
+            console.log(a, b);
+        };
+        var a = "foo", b = 42;
+        f();
+        b = "bar";
+        f();
+    }
+    expect: {
+        var f = () => {
+            console.log("foo", b);
+        };
+        var b = 42;
+        f();
+        b = "bar";
+        f();
+    }
+    expect_stdout: [
+        "foo 42",
+        "foo bar",
+    ]
+    node_version: ">=4"
+}
+
+reduce_lambda_2: {
+    options = {
+        evaluate: true,
+        passes: 2,
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        (function(f, a, b) {
+            f = () => {
+                console.log(a, b);
+            };
+            a = "foo", b = 42;
+            f();
+            b = "bar";
+            f();
+        })();
+    }
+    expect: {
+        (function(f, a, b) {
+            f = () => {
+                console.log("foo", b);
+            };
+            b = 42;
+            f();
+            b = "bar";
+            f();
+        })();
+    }
+    expect_stdout: [
+        "foo 42",
+        "foo bar",
+    ]
+    node_version: ">=4"
+}
+
 single_use_recursive: {
    options = {
        reduce_vars: true,
@@ -814,3 +906,24 @@ issue_4772: {
    expect_stdout: "PASS"
    node_version: ">=4"
 }
+
+issue_5251: {
+    options = {
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        (() => {
+            while (console.log(arguments))
+                var arguments = "FAIL";
+        })();
+    }
+    expect: {
+        (() => {
+            while (console.log(arguments))
+                var arguments = "FAIL";
+        })();
+    }
+    expect_stdout: true
+    node_version: ">=4"
+}
--- a/test/compress/assignments.js
+++ b/test/compress/assignments.js
@@ -475,3 +475,332 @@ issue_4521: {
    }
    expect_stdout: "42"
 }
+
+logical_assignments: {
+    input: {
+        var a = 42, b = null, c;
+        a &&= "foo";
+        b ||= "bar";
+        c ??= "baz";
+        console.log(a, b, c);
+    }
+    expect_exact: 'var a=42,b=null,c;a&&="foo";b||="bar";c??="baz";console.log(a,b,c);'
+    expect_stdout: "foo bar baz"
+    node_version: ">=15"
+}
+
+logical_collapse_vars_1: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = "FAIL", b = false;
+        a = "PASS";
+        b ??= a;
+        console.log(a);
+    }
+    expect: {
+        var a = "FAIL", b = false;
+        a = "PASS";
+        b ??= a;
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+logical_collapse_vars_2: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = "PASS";
+        (function(b) {
+            b ||= (a = "FAIL", {});
+            return b;
+        })(console).log(a);
+    }
+    expect: {
+        var a = "PASS";
+        (function(b) {
+            return b ||= (a = "FAIL", {});
+        })(console).log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+logical_collapse_vars_3: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = 6;
+        a *= 7;
+        a ??= "FAIL";
+        console.log(a);
+    }
+    expect: {
+        var a = 6;
+        a = a * 7 ?? "FAIL";
+        console.log(a);
+    }
+    expect_stdout: "42"
+    node_version: ">=15"
+}
+
+logical_reduce_vars: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS", b = 42;
+        b ??= a = "FAIL";
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS", b = 42;
+        b ??= a = "FAIL";
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+logical_side_effects: {
+    options = {
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS", b = 42;
+        b ??= a = "FAIL";
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS", b = 42;
+        b ??= a = "FAIL";
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+evaluate_lazy_assignment: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = 42;
+        console.log(a &&= "PASS");
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+issue_4815_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        42..p &&= a = "FAIL";
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS";
+        42..p &&= a = "FAIL";
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+issue_4815_2: {
+    options = {
+        pure_getters: "strict",
+        side_effects: true,
+    }
+    input: {
+        var a = "PASS";
+        42..p &&= a = "FAIL";
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS";
+        42..p &&= a = "FAIL";
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+issue_4819: {
+    options = {
+        comparisons: true,
+    }
+    input: {
+        console.log(void 0 === ([].p &&= 42));
+    }
+    expect: {
+        console.log(void 0 === ([].p &&= 42));
+    }
+    expect_stdout: "true"
+    node_version: ">=15"
+}
+
+issue_4827_1: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+    }
+    input: {
+        A = "FAIL";
+        var a = A, b = "PASS", c;
+        c &&= b = a, console.log(b);
+    }
+    expect: {
+        A = "FAIL";
+        var a = A, b = "PASS", c;
+        c &&= b = a, console.log(b);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+issue_4827_2: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = 0, b = "PASS";
+        function f(c) {
+            a++,
+            c &&= b = a;
+        }
+        f();
+        console.log(b);
+    }
+    expect: {
+        var a = 0, b = "PASS";
+        a++,
+        c &&= b = a;
+        var c;
+        console.log(b);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+issue_4827_3: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 0, b, c;
+        a++;
+        c &&= b = a;
+        console.log(b);
+    }
+    expect: {
+        var a = 0, b, c;
+        a++;
+        c &&= b = a;
+        console.log(b);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=15"
+}
+
+issue_4876: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        try {
+            var a = null;
+            var b = a &&= 42;
+            b.p;
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            var a = null;
+            var b = a &&= 42;
+            b.p;
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+issue_4924_1: {
+    options = {
+        collapse_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a, b;
+        console.log("PASS");
+        a = function() {};
+        b = function() {}(b ||= a);
+    }
+    expect: {
+        var b;
+        console.log("PASS");
+        b = void (b ||= function() {});
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+issue_4924_2: {
+    options = {
+        collapse_vars: true,
+        dead_code: true,
+        passes: 2,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a, b;
+        console.log("PASS");
+        a = function() {};
+        b = function() {}(b ||= a);
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
--- a/test/compress/awaits.js
+++ b/test/compress/awaits.js
--- a/test/compress/bigint.js
+++ b/test/compress/bigint.js
@@ -4,7 +4,7 @@ arithmetic: {
    }
    expect_exact: "console.log((1n+0x2n)*(0o3n- -4n)>>5n-6n);"
    expect_stdout: "42n"
-    node_version: ">=10"
+    node_version: ">=10.4.0"
 }

 minus_dot: {
@@ -13,7 +13,7 @@ minus_dot: {
    }
    expect_exact: "console.log(typeof-42n.toString(),typeof(-42n).toString());"
    expect_stdout: "number string"
-    node_version: ">=10"
+    node_version: ">=10.4.0"
 }

 evaluate: {
@@ -28,7 +28,7 @@ evaluate: {
        console.log(0xdeadbeefn.toString(16));
    }
    expect_stdout: "deadbeef"
-    node_version: ">=10"
+    node_version: ">=10.4.0"
 }

 Number: {
@@ -42,7 +42,7 @@ Number: {
        console.log(+("" + -0xfeed_dead_beef_badn));
    }
    expect_stdout: "-1148098955808013200"
-    node_version: ">=10"
+    node_version: ">=10.4.0"
 }

 issue_4590: {
@@ -58,7 +58,7 @@ issue_4590: {
        0n || console.log("PASS");
    }
    expect_stdout: "PASS"
-    node_version: ">=10"
+    node_version: ">=10.4.0"
 }

 issue_4801: {
@@ -88,5 +88,5 @@ issue_4801: {
        }
    }
    expect_stdout: "PASS"
-    node_version: ">=10"
+    node_version: ">=10.4.0"
 }
--- a/test/compress/booleans.js
+++ b/test/compress/booleans.js
@@ -29,6 +29,404 @@ iife_boolean_context: {
    ]
 }

+de_morgan_1a: {
+    options = {
+        booleans: true,
+    }
+    input: {
+        function f(a) {
+            return a || a;
+        }
+        console.log(f(null), f(42));
+    }
+    expect: {
+        function f(a) {
+            return a;
+        }
+        console.log(f(null), f(42));
+    }
+    expect_stdout: "null 42"
+}
+
+de_morgan_1b: {
+    options = {
+        booleans: true,
+    }
+    input: {
+        function f(a) {
+            return a && a;
+        }
+        console.log(f(null), f(42));
+    }
+    expect: {
+        function f(a) {
+            return a;
+        }
+        console.log(f(null), f(42));
+    }
+    expect_stdout: "null 42"
+}
+
+de_morgan_1c: {
+    options = {
+        booleans: true,
+    }
+    input: {
+        console.log(delete (NaN && NaN));
+    }
+    expect: {
+        console.log(delete (0, NaN));
+    }
+    expect_stdout: "true"
+}
+
+de_morgan_2a: {
+    options = {
+        booleans: true,
+        conditionals: true,
+    }
+    input: {
+        function f(a, b) {
+            return a || (a || b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a || b;
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "undefined {}",
+        "42 42",
+    ]
+}
+
+de_morgan_2b: {
+    options = {
+        booleans: true,
+        evaluate: true,
+    }
+    input: {
+        function f(a, b) {
+            return a || (a && b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a;
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "null null",
+        "42 42",
+    ]
+}
+
+de_morgan_2c: {
+    options = {
+        booleans: true,
+        evaluate: true,
+    }
+    input: {
+        function f(a, b) {
+            return a && (a || b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a;
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "null null",
+        "42 42",
+    ]
+}
+
+de_morgan_2d: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        function f(a, b) {
+            return a && (a && b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a && b;
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "null null",
+        "undefined {}",
+    ]
+}
+
+de_morgan_3a: {
+    options = {
+        booleans: true,
+        conditionals: true,
+    }
+    input: {
+        function f(a, b, c) {
+            return a || ((a || b) || c);
+        }
+        console.log(f(null, false), f(null, false, {}), f(null, true), f(null, true, {}));
+        console.log(f(42, false), f(42, false, {}), f(42, true), f(42, true, {}));
+    }
+    expect: {
+        function f(a, b, c) {
+            return a || b || c;
+        }
+        console.log(f(null, !1), f(null, !1, {}), f(null, !0), f(null, !0, {}));
+        console.log(f(42, !1), f(42, !1, {}), f(42, !0), f(42, !0, {}));
+    }
+    expect_stdout: [
+        "undefined {} true true",
+        "42 42 42 42",
+    ]
+}
+
+de_morgan_3b: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        function f(a, b, c) {
+            return a || ((a || b) && c);
+        }
+        console.log(f(null, false), f(null, false, {}), f(null, true), f(null, true, {}));
+        console.log(f(42, false), f(42, false, {}), f(42, true), f(42, true, {}));
+    }
+    expect: {
+        function f(a, b, c) {
+            return a || b && c;
+        }
+        console.log(f(null, !1), f(null, !1, {}), f(null, !0), f(null, !0, {}));
+        console.log(f(42, !1), f(42, !1, {}), f(42, !0), f(42, !0, {}));
+    }
+    expect_stdout: [
+        "false false undefined {}",
+        "42 42 42 42",
+    ]
+}
+
+de_morgan_3c: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        function f(a, b, c) {
+            return a || ((a && b) || c);
+        }
+        console.log(f(null, false), f(null, false, {}), f(null, true), f(null, true, {}));
+        console.log(f(42, false), f(42, false, {}), f(42, true), f(42, true, {}));
+    }
+    expect: {
+        function f(a, b, c) {
+            return a || c;
+        }
+        console.log(f(null, !1), f(null, !1, {}), f(null, !0), f(null, !0, {}));
+        console.log(f(42, !1), f(42, !1, {}), f(42, !0), f(42, !0, {}));
+    }
+    expect_stdout: [
+        "undefined {} undefined {}",
+        "42 42 42 42",
+    ]
+}
+
+de_morgan_3d: {
+    options = {
+        booleans: true,
+        evaluate: true,
+    }
+    input: {
+        function f(a, b, c) {
+            return a || ((a && b) && c);
+        }
+        console.log(f(null, false), f(null, false, {}), f(null, true), f(null, true, {}));
+        console.log(f(42, false), f(42, false, {}), f(42, true), f(42, true, {}));
+    }
+    expect: {
+        function f(a, b, c) {
+            return a;
+        }
+        console.log(f(null, !1), f(null, !1, {}), f(null, !0), f(null, !0, {}));
+        console.log(f(42, !1), f(42, !1, {}), f(42, !0), f(42, !0, {}));
+    }
+    expect_stdout: [
+        "null null null null",
+        "42 42 42 42",
+    ]
+}
+
+de_morgan_3e: {
+    options = {
+        booleans: true,
+        evaluate: true,
+    }
+    input: {
+        function f(a, b, c) {
+            return a && ((a || b) || c);
+        }
+        console.log(f(null, false), f(null, false, {}), f(null, true), f(null, true, {}));
+        console.log(f(42, false), f(42, false, {}), f(42, true), f(42, true, {}));
+    }
+    expect: {
+        function f(a, b, c) {
+            return a;
+        }
+        console.log(f(null, !1), f(null, !1, {}), f(null, !0), f(null, !0, {}));
+        console.log(f(42, !1), f(42, !1, {}), f(42, !0), f(42, !0, {}));
+    }
+    expect_stdout: [
+        "null null null null",
+        "42 42 42 42",
+    ]
+}
+
+de_morgan_3f: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        function f(a, b, c) {
+            return a && ((a || b) && c);
+        }
+        console.log(f(null, false), f(null, false, {}), f(null, true), f(null, true, {}));
+        console.log(f(42, false), f(42, false, {}), f(42, true), f(42, true, {}));
+    }
+    expect: {
+        function f(a, b, c) {
+            return a && c;
+        }
+        console.log(f(null, !1), f(null, !1, {}), f(null, !0), f(null, !0, {}));
+        console.log(f(42, !1), f(42, !1, {}), f(42, !0), f(42, !0, {}));
+    }
+    expect_stdout: [
+        "null null null null",
+        "undefined {} undefined {}",
+    ]
+}
+
+de_morgan_3g: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        function f(a, b, c) {
+            return a && ((a && b) || c);
+        }
+        console.log(f(null, false), f(null, false, {}), f(null, true), f(null, true, {}));
+        console.log(f(42, false), f(42, false, {}), f(42, true), f(42, true, {}));
+    }
+    expect: {
+        function f(a, b, c) {
+            return a && (b || c);
+        }
+        console.log(f(null, !1), f(null, !1, {}), f(null, !0), f(null, !0, {}));
+        console.log(f(42, !1), f(42, !1, {}), f(42, !0), f(42, !0, {}));
+    }
+    expect_stdout: [
+        "null null null null",
+        "undefined {} true true",
+    ]
+}
+
+de_morgan_3h: {
+    options = {
+        booleans: true,
+        conditionals: true,
+    }
+    input: {
+        function f(a, b, c) {
+            return a && ((a && b) && c);
+        }
+        console.log(f(null, false), f(null, false, {}), f(null, true), f(null, true, {}));
+        console.log(f(42, false), f(42, false, {}), f(42, true), f(42, true, {}));
+    }
+    expect: {
+        function f(a, b, c) {
+            return a && b && c;
+        }
+        console.log(f(null, !1), f(null, !1, {}), f(null, !0), f(null, !0, {}));
+        console.log(f(42, !1), f(42, !1, {}), f(42, !0), f(42, !0, {}));
+    }
+    expect_stdout: [
+        "null null null null",
+        "false false undefined {}",
+    ]
+}
+
+conditional_chain: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        evaluate: true,
+    }
+    input: {
+        function f(a, b) {
+            return a ? a : b ? b : 42;
+        }
+        console.log(f("PASS", "FAIL"));
+    }
+    expect: {
+        function f(a, b) {
+            return a || b || 42;
+        }
+        console.log(f("PASS", "FAIL"));
+    }
+    expect_stdout: "PASS"
+}
+
+negated_if: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(function(a) {
+            if (!a)
+                return a ? "FAIL" : "PASS";
+        }(!console));
+    }
+    expect: {
+        console.log(function(a) {
+            if (!a)
+                return "PASS";
+        }(!console));
+    }
+    expect_stdout: "PASS"
+}
+
 issue_3465_1: {
    options = {
        booleans: true,
@@ -181,3 +579,148 @@ issue_4374: {
    }
    expect_stdout: "0"
 }
+
+issue_5028_1: {
+    options = {
+        booleans: true,
+        conditionals: true,
+    }
+    input: {
+        var a = 1;
+        console.log(function() {
+            return a-- ? a-- ? "FAIL 1" : "PASS" : "FAIL 2";
+        }());
+    }
+    expect: {
+        var a = 1;
+        console.log(function() {
+            return a-- ? a-- ? "FAIL 1" : "PASS" : "FAIL 2";
+        }());
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5028_2: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        dead_code: true,
+        if_return: true,
+    }
+    input: {
+        var a = 1;
+        (function() {
+            if (a--)
+                if (a--)
+                    a = "FAIL";
+                else
+                    return;
+        })();
+        console.log(a);
+    }
+    expect: {
+        var a = 1;
+        (function() {
+            a-- && a-- && (a = "FAIL");
+        })();
+        console.log(a);
+    }
+    expect_stdout: "-1"
+}
+
+issue_5028_3: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        evaluate: true,
+        if_return: true,
+    }
+    input: {
+        var a = 1;
+        (function() {
+            if (a--)
+                if (a--)
+                    a = "FAIL";
+                else
+                    return;
+        })();
+        console.log(a);
+    }
+    expect: {
+        var a = 1;
+        (function() {
+            a-- && a-- && (a = "FAIL");
+        })();
+        console.log(a);
+    }
+    expect_stdout: "-1"
+}
+
+issue_5041_1: {
+    options = {
+        booleans: true,
+        conditionals: true,
+    }
+    input: {
+        var a = 42;
+        if (a)
+            if ([ a = null ])
+                if (a)
+                    console.log("FAIL");
+                else
+                    console.log("PASS");
+    }
+    expect: {
+        var a = 42;
+        a && [ a = null ] && (a ? console.log("FAIL") : console.log("PASS"));
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5041_2: {
+    options = {
+        booleans: true,
+        conditionals: true,
+    }
+    input: {
+        var a;
+        if (!a)
+            if (a = 42)
+                if (a)
+                    console.log("PASS");
+                else
+                    console.log("FAIL");
+    }
+    expect: {
+        var a;
+        a || (a = 42) && (a ? console.log("PASS") : console.log("FAIL"));
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5228: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        inline: true,
+        passes: 2,
+    }
+    input: {
+        console.log(function() {
+            return !function() {
+                do {
+                    return null;
+                } while (console);
+            }();
+        }());
+    }
+    expect: {
+        console.log(function() {
+            do {
+                return !0;
+            } while (console);
+            return !0;
+        }());
+    }
+    expect_stdout: "true"
+}
--- a/test/compress/classes.js
+++ b/test/compress/classes.js
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
--- a/test/compress/concat-strings.js
+++ b/test/compress/concat-strings.js
@@ -289,3 +289,18 @@ issue_3689: {
    }
    expect_stdout: "00"
 }
+
+issue_5145: {
+    options = {
+        strings: true,
+    }
+    input: {
+        var a = [];
+        console.log("" + a + ((a[0] = 4) + "2"));
+    }
+    expect: {
+        var a = [];
+        console.log("" + a + (a[0] = 4) + "2");
+    }
+    expect_stdout: "42"
+}
--- a/test/compress/conditionals.js
+++ b/test/compress/conditionals.js
@@ -822,6 +822,33 @@ cond_13: {
    }
 }

+cond_14: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        side_effects: true,
+    }
+    input: {
+        function f(a) {
+            if (a)
+                if (a)
+                    console.log("PASS");
+                else
+                    console.log("FAIL");
+        }
+        f(null);
+        f(42);
+    }
+    expect: {
+        function f(a) {
+            a && console.log("PASS");
+        }
+        f(null);
+        f(42);
+    }
+    expect_stdout: "PASS"
+}
+
 ternary_boolean_consequent: {
    options = {
        booleans: true,
@@ -1897,3 +1924,86 @@ object_super: {
    expect_stdout: "PASS"
    node_version: ">=4"
 }
+
+issue_5232_1: {
+    options = {
+        conditionals: true,
+    }
+    input: {
+        (function() {
+            if (Math) {
+                function f() {}
+                for (var a in [ 42 ])
+                    console.log(typeof f);
+            } else {
+                var b = null;
+                return true;
+            }
+        })();
+    }
+    expect: {
+        (function() {
+            var b;
+            if (!Math)
+                return b = null, true;
+            function f() {}
+            for (var a in [ 42 ]) console.log(typeof f);
+        })();
+    }
+    expect_stdout: "function"
+}
+
+issue_5232_2: {
+    options = {
+        conditionals: true,
+    }
+    input: {
+        console.log(function() {
+            if (!Math);
+            else {
+                var b = null;
+                return "PASS";
+            }
+        }());
+    }
+    expect: {
+        console.log(function() {
+            var b;
+            if (Math)
+                return b = null, "PASS";
+        }());
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5232_3: {
+    options = {
+        conditionals: true,
+    }
+    input: {
+        console.log(function() {
+            return function() {
+                if (console)
+                    console.log("PASS");
+                else {
+                    var a = null;
+                    return "FAIL";
+                }
+            };
+        }()());
+    }
+    expect: {
+        console.log(function() {
+            return function() {
+                var a;
+                if (!console)
+                    return a = null, "FAIL";
+                console.log("PASS");
+            };
+        }()());
+    }
+    expect_stdout: [
+        "PASS",
+        "undefined",
+    ]
+}
--- a/test/compress/const.js
+++ b/test/compress/const.js
@@ -220,6 +220,32 @@ merge_vars_3: {
    expect_stdout: true
 }

+merge_vars_4: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 1;
+        console.log(typeof a);
+        {
+            var b = console;
+            console.log(typeof b);
+            const a = 0;
+        }
+    }
+    expect: {
+        var a = 1;
+        console.log(typeof a);
+        {
+            var b = console;
+            console.log(typeof b);
+            const a = 0;
+        }
+    }
+    expect_stdout: true
+}
+
 use_before_init_1: {
    options = {
        reduce_vars: true,
@@ -486,7 +512,7 @@ do_continue: {

 catch_ie8_1: {
    options = {
-        ie8: true,
+        ie: true,
        unused: true,
    }
    input: {
@@ -506,7 +532,7 @@ catch_ie8_1: {
 catch_ie8_2: {
    options = {
        dead_code: true,
-        ie8: true,
+        ie: true,
        passes: 2,
        toplevel: true,
        unused: true,
@@ -727,7 +753,7 @@ issue_4193: {

 issue_4195: {
    mangle = {
-        ie8: true,
+        ie: true,
    }
    input: {
        console.log(function f(a) {
@@ -838,12 +864,10 @@ issue_4202: {
    expect: {
        {
            const o = {};
-            (function() {
-                function f() {
-                    o.p = 42;
-                }
-                f(f);
-            })();
+            function f() {
+                o.p = 42;
+            }
+            f(f);
            console.log(o.p++);
        }
    }
@@ -1131,7 +1155,7 @@ issue_4225: {

 issue_4229: {
    options = {
-        ie8: true,
+        ie: true,
        side_effects: true,
    }
    input: {
@@ -1151,7 +1175,7 @@ issue_4229: {

 issue_4231: {
    options = {
-        ie8: true,
+        ie: true,
        side_effects: true,
    }
    input: {
@@ -1219,9 +1243,9 @@ issue_4248: {
    expect_stdout: "PASS"
 }

-issue_4261: {
+issue_4261_1: {
    options = {
-        inline: true,
+        inline: 3,
        reduce_funcs: true,
        reduce_vars: true,
        toplevel: true,
@@ -1259,6 +1283,43 @@ issue_4261: {
    expect_stdout: "42"
 }

+issue_4261_2: {
+    options = {
+        if_return: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        {
+            const a = 42;
+            (function() {
+                function f() {
+                    console.log(a);
+                }
+                function g() {
+                    while (f());
+                }
+                (function() {
+                    while (g());
+                })();
+            })();
+        }
+    }
+    expect: {
+        {
+            const a = 42;
+            function g() {
+                while (void console.log(a));
+            }
+            while (g());
+        }
+    }
+    expect_stdout: "42"
+}
+
 issue_4274_1: {
    options = {
        loops: true,
@@ -1498,3 +1559,257 @@ issue_4691: {
    }
    expect_stdout: "PASS"
 }
+
+issue_4848: {
+    options = {
+        if_return: true,
+    }
+    input: {
+        function f(a) {
+            a(function() {
+                console.log(b);
+            });
+            if (!console)
+                return;
+            const b = "PASS";
+        }
+        var g;
+        f(function(h) {
+            g = h;
+        });
+        g();
+    }
+    expect: {
+        function f(a) {
+            a(function() {
+                console.log(b);
+            });
+            if (!console)
+                return;
+            const b = "PASS";
+        }
+        var g;
+        f(function(h) {
+            g = h;
+        });
+        g();
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4954_1: {
+    rename = true
+    input: {
+        "use strict";
+        (function() {
+            {
+                const a = "foo";
+                console.log(a);
+            }
+            {
+                const a = "bar";
+                console.log(a);
+            }
+        })();
+    }
+    expect: {
+        "use strict";
+        (function() {
+            {
+                const a = "foo";
+                console.log(a);
+            }
+            {
+                const b = "bar";
+                console.log(b);
+            }
+        })();
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+    node_version: ">=4"
+}
+
+issue_4954_2: {
+    mangle = {}
+    input: {
+        "use strict";
+        const a = null;
+        (function(b) {
+            for (const a in null);
+            for (const a in b)
+                console.log("PASS");
+        })([ null ]);
+    }
+    expect: {
+        "use strict";
+        const a = null;
+        (function(o) {
+            for (const n in null);
+            for (const n in o)
+                console.log("PASS");
+        })([ null ]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_4960: {
+    mangle = {}
+    input: {
+        "use strict";
+        var a;
+        (function() {
+            {
+                const a = console.log("PASS");
+            }
+            try {} catch (e) {
+                const a = console.log("FAIL");
+            }
+        })();
+    }
+    expect: {
+        "use strict";
+        var a;
+        (function() {
+            {
+                const o = console.log("PASS");
+            }
+            try {} catch (o) {
+                const c = console.log("FAIL");
+            }
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_4965_1: {
+    mangle = {}
+    input: {
+        "use strict";
+        try {
+            c;
+        } catch (a) {
+            {
+                const a = 1;
+            }
+            {
+                const a = console.log(typeof c);
+            }
+        }
+    }
+    expect: {
+        "use strict";
+        try {
+            c;
+        } catch (t) {
+            {
+                const c = 1;
+            }
+            {
+                const t = console.log(typeof c);
+            }
+        }
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}
+
+issue_4965_2: {
+    mangle = {}
+    input: {
+        "use strict";
+        try {
+            throw 1;
+        } catch (e) {
+            try {
+                {
+                    const e = 2;
+                }
+            } finally {
+                const e = 3;
+                console.log(typeof t);
+            }
+        }
+    }
+    expect: {
+        "use strict";
+        try {
+            throw 1;
+        } catch (o) {
+            try {
+                {
+                    const t = 2;
+                }
+            } finally {
+                const o = 3;
+                console.log(typeof t);
+            }
+        }
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}
+
+issue_5254: {
+    options = {
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        do {
+            (function() {
+                const a = console.log;
+                a && a("foo");
+            })();
+        } while (console.log("bar"));
+    }
+    expect: {
+        do {
+            const a = console.log;
+            a && a("foo");
+        } while (console.log("bar"));
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+}
+
+issue_5260: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        "use strict";
+        var a = "foo", o;
+        while (console.log("bar"));
+        o = {
+            baz: function(b) {
+                console.log(a, b);
+            },
+        };
+        for (const a in o)
+            o[a](a);
+    }
+    expect: {
+        "use strict";
+        var a = "foo", o;
+        while (console.log("bar"));
+        o = {
+            baz: function(b) {
+                console.log(a, b);
+            },
+        };
+        for (const a in o)
+            o[a](a);
+    }
+    expect_stdout: [
+        "bar",
+        "foo baz",
+    ]
+    node_version: ">=4"
+}
--- a/test/compress/dead-code.js
+++ b/test/compress/dead-code.js
@@ -939,6 +939,185 @@ catch_return_assign: {
    expect_stdout: "PASS"
 }

+catch_return_assign_may_throw: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        function f() {
+            try {
+                throw "FAIL";
+            } catch (e) {
+                return e = console.log("PASS");
+            }
+        }
+        f();
+    }
+    expect: {
+        function f() {
+            try {
+                throw "FAIL";
+            } catch (e) {
+                return console.log("PASS");
+            }
+        }
+        f();
+    }
+    expect_stdout: "PASS"
+}
+
+finally_return_assign: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        console.log(function(a) {
+            try {
+                throw "FAIL";
+            } finally {
+                return a = "PASS";
+            }
+        }());
+    }
+    expect: {
+        console.log(function(a) {
+            try {
+                throw "FAIL";
+            } finally {
+                return "PASS";
+            }
+        }());
+    }
+    expect_stdout: "PASS"
+}
+
+last_assign_statement: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        function f(a) {
+            a = a("PASS");
+        }
+        f(console.log);
+    }
+    expect: {
+        function f(a) {
+            a("PASS");
+        }
+        f(console.log);
+    }
+    expect_stdout: "PASS"
+}
+
+last_assign_if_else: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        function f(a) {
+            if (a)
+                a = console.log("foo");
+            else {
+                console.log("bar");
+                a = console.log("baz");
+            }
+        }
+        f(42);
+        f(null);
+    }
+    expect: {
+        function f(a) {
+            if (a)
+                console.log("foo");
+            else {
+                console.log("bar");
+                console.log("baz");
+            }
+        }
+        f(42);
+        f(null);
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+        "baz",
+    ]
+}
+
+last_assign_catch: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        function f() {
+            try {
+                throw "FAIL";
+            } catch (e) {
+                e = console.log("PASS");
+            }
+        }
+        f();
+    }
+    expect: {
+        function f() {
+            try {
+                throw "FAIL";
+            } catch (e) {
+                console.log("PASS");
+            }
+        }
+        f();
+    }
+    expect_stdout: "PASS"
+}
+
+last_assign_finally: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        function f(a) {
+            try {
+                throw a.log;
+            } catch (e) {
+                a = e;
+            } finally {
+                a = a("PASS");
+            }
+        }
+        f(console);
+    }
+    expect: {
+        function f(a) {
+            try {
+                throw a.log;
+            } catch (e) {
+                a = e;
+            } finally {
+                a("PASS");
+            }
+        }
+        f(console);
+    }
+    expect_stdout: "PASS"
+}
+
+consecutive_assignments: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        while (a = void 0, a = "PASS", console.log(a));
+        var a;
+    }
+    expect: {
+        while (void 0, a = "PASS", console.log(a));
+        var a;
+    }
+    expect_stdout: "PASS"
+}
+
 issue_3578: {
    options = {
        dead_code: true,
@@ -1420,3 +1599,73 @@ issue_4570: {
    }
    expect_stdout: "NaN"
 }
+
+issue_5030: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        (function(a, b) {
+            a = function f() {
+                if (a)
+                    if (b--)
+                        setImmediate(f);
+                    else
+                        console.log("FAIL");
+                else
+                    console.log("PASS");
+            }();
+        })(42, 1);
+    }
+    expect: {
+        (function(a, b) {
+            a = function f() {
+                if (a)
+                    if (b--)
+                        setImmediate(f);
+                    else
+                        console.log("FAIL");
+                else
+                    console.log("PASS");
+            }();
+        })(42, 1);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=0.12"
+}
+
+issue_5106_1: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        console.log(typeof function(a) {
+            return a = arguments;
+        }("FAIL")[0]);
+    }
+    expect: {
+        console.log(typeof function(a) {
+            return a = arguments;
+        }("FAIL")[0]);
+    }
+    expect_stdout: "object"
+}
+
+issue_5106_2: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        "use strict";
+        console.log(function(a) {
+            return a = arguments;
+        }("PASS")[0]);
+    }
+    expect: {
+        "use strict";
+        console.log(function(a) {
+            return arguments;
+        }("PASS")[0]);
+    }
+    expect_stdout: "PASS"
+}
--- a/test/compress/default-values.js
+++ b/test/compress/default-values.js
@@ -70,7 +70,7 @@ object_shorthand_assign: {
        ({ a = "PASS" } = 42);
        console.log(a);
    }
-    expect_exact: '({a:a="PASS"}=42);console.log(a);'
+    expect_exact: '({a="PASS"}=42);console.log(a);'
    expect_stdout: "PASS"
    node_version: ">=6"
 }
@@ -80,7 +80,7 @@ object_shorthand_declaration: {
        var { a = "PASS" } = 42;
        console.log(a);
    }
-    expect_exact: 'var{a:a="PASS"}=42;console.log(a);'
+    expect_exact: 'var{a="PASS"}=42;console.log(a);'
    expect_stdout: "PASS"
    node_version: ">=6"
 }
@@ -91,7 +91,7 @@ object_shorthand_function: {
            console.log(a);
        })(42);
    }
-    expect_exact: '(function({a:a="PASS"}){console.log(a)})(42);'
+    expect_exact: '(function({a="PASS"}){console.log(a)})(42);'
    expect_stdout: "PASS"
    node_version: ">=6"
 }
@@ -149,7 +149,7 @@ process_boolean_returns: {
    }
    expect: {
        console.log(function(a = console.log("FAIL 1")) {
-            return a() ? "PASS" : "FAIL 2";
+            return 42 ? "PASS" : "FAIL 2";
        }(function() {
            return 1;
        }));
@@ -158,6 +158,28 @@ process_boolean_returns: {
    node_version: ">=6"
 }

+collapse_arg_sequence: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a = (console.log("bar"), console.log)) {
+            a("foo");
+        })();
+    }
+    expect: {
+        (function(a = console.log("bar")) {
+            (0, console.log)("foo");
+        })();
+    }
+    expect_stdout: [
+        "bar",
+        "foo",
+    ]
+    node_version: ">=6"
+}
+
 collapse_value_1: {
    options = {
        collapse_vars: true,
@@ -245,21 +267,64 @@ maintain_if: {
    node_version: ">=6"
 }

-reduce_value: {
+reduce_funarg: {
    options = {
        evaluate: true,
+        keep_fargs: false,
        reduce_vars: true,
        unused: true,
    }
    input: {
-        console.log(function(a = "PASS") {
-            return a;
-        }());
+        console.log(...function(a = "foo", b = "bar", c = "baz") {
+            return [ a, b, c ];
+        }(void 0, null));
    }
    expect: {
-        console.log("PASS");
+        console.log(...function() {
+            return [ "foo", null, "baz" ];
+        }());
    }
-    expect_stdout: "PASS"
+    expect_stdout: "foo null baz"
+    node_version: ">=6"
+}
+
+reduce_array: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var [ a = "foo", b = "bar", c = "baz" ] = [ void 0, null ];
+        console.log(a, b, c);
+    }
+    expect: {
+        var [ c = "baz" ] = [];
+        console.log("foo", null, c);
+    }
+    expect_stdout: "foo null baz"
+    node_version: ">=6"
+}
+
+reduce_object: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var { a = "foo", b = "bar", c = "baz" } = { a: void 0, b: null };
+        console.log(a, b, c);
+    }
+    expect: {
+        var { c = "baz" } = {};
+        console.log("foo", null, c);
+    }
+    expect_stdout: "foo null baz"
    node_version: ">=6"
 }

@@ -422,7 +487,9 @@ inline_loop_1: {
 inline_loop_2: {
    options = {
        inline: true,
+        sequences: true,
        toplevel: true,
+        unused: true,
    }
    input: {
        while (function(a = [ "PASS" ]) {
@@ -432,10 +499,11 @@ inline_loop_2: {
        }());
    }
    expect: {
-        while (a = [ "PASS" ], a = function f(b) {
-            console.log(a[b]);
-        }(0), void 0) ;
-        var a;
+        while (a = [ "PASS" ],
+            b = void 0,
+            b = 0,
+            void (a = void console.log(a[b])));
+        var a, b;
    }
    expect_stdout: "PASS"
    node_version: ">=6"
@@ -522,6 +590,20 @@ retain_empty_iife: {
    node_version: ">=6"
 }

+drop_new_function: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        new function(a = console.log("PASS")) {}();
+    }
+    expect: {
+        void console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 retain_fargs: {
    options = {
        unused: true,
@@ -598,6 +680,7 @@ unused_var_1: {

 unused_var_2: {
    options = {
+        pure_getters: "strict",
        toplevel: true,
        unused: true,
    }
@@ -609,11 +692,7 @@ unused_var_2: {
        };
    }
    expect: {
-        var {
-            p: [] = [ console.log("FAIL") ],
-        } = {
-            p: [ console.log("PASS") ],
-        };
+        console.log("PASS");
    }
    expect_stdout: "PASS"
    node_version: ">=6"
@@ -676,7 +755,7 @@ unused_value_var_2: {
        console.log(a);
    }
    expect: {
-        var [ a ] = [ "PASS" ];
+        var a = [ "PASS" ][0];
        console.log(a);
    }
    expect_stdout: "PASS"
@@ -980,7 +1059,7 @@ mangle_arrow_1: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.3"
 }

 mangle_arrow_1_toplevel: {
@@ -1016,7 +1095,7 @@ mangle_arrow_1_toplevel: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.3"
 }

 mangle_arrow_2: {
@@ -1052,7 +1131,7 @@ mangle_arrow_2: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.3"
 }

 mangle_arrow_2_toplevel: {
@@ -1088,7 +1167,7 @@ mangle_arrow_2_toplevel: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.3"
 }

 issue_4444: {
@@ -1257,7 +1336,7 @@ issue_4468: {
    expect: {
        (function() {
            var {
-                [console.log("PASS")]: b = 0,
+                [console.log("PASS")]: b,
            } = 0;
        })();
    }
@@ -1416,6 +1495,7 @@ issue_4502_1: {
    expect: {
        (function() {
            var a = "PASS";
+            void 0,
            console.log(a),
            a++,
            void 0;
@@ -1439,6 +1519,7 @@ issue_4502_2: {
    expect: {
        (function() {
            var a = "PASS";
+            void 0,
            console.log(a),
            a++,
            void 0;
@@ -1528,7 +1609,7 @@ issue_4510_2: {
        };
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4523: {
@@ -1661,3 +1742,342 @@ issue_4588_2_evaluate: {
    expect_stdout: "1"
    node_version: ">=6"
 }
+
+issue_4817: {
+    options = {
+        ie: true,
+        inline: true,
+        unused: true,
+    }
+    input: {
+        (function f(a = console.log(typeof f)) {
+            return 42;
+        })();
+    }
+    expect: {
+        (function f(a = console.log(typeof f)) {
+            return 42;
+        })();
+    }
+    expect_stdout: "function"
+    node_version: ">=6"
+}
+
+issue_4854: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            (function(b = a = "foo") {
+                [] = "foo";
+            })();
+            a;
+        }());
+    }
+    expect: {
+        console.log(void 0);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+issue_4916: {
+    options = {
+        collapse_vars: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+    }
+    input: {
+        var log = console.log;
+        (function(b = "foo") {
+            b.value = "FAIL";
+            b;
+            log(b.value);
+        })();
+    }
+    expect: {
+        var log = console.log;
+        (function(b = "foo") {
+            b.value = "FAIL";
+            b;
+            log(b.value);
+        })();
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+issue_4994: {
+    options = {
+        loops: true,
+        unused: true,
+    }
+    input: {
+        var a = "FAIL";
+        (function(b = function() {
+            for (a in { PASS: 42 });
+        }()) {
+            var a;
+        })();
+        console.log(a);
+    }
+    expect: {
+        var a = "FAIL";
+        (function(b = function() {
+            for (a in { PASS: 42 });
+        }()) {})();
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5057_1: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        sequences: true,
+        unused: true,
+    }
+    input: {
+        var a = 42;
+        (function() {
+            var b = function(c = (console.log("foo"), b = a)) {
+                a && console.log("bar");
+            }();
+        })();
+    }
+    expect: {
+        var a = 42;
+        console.log("foo"),
+        void (a && console.log("bar"));
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+    node_version: ">=6"
+}
+
+issue_5057_2: {
+    options = {
+        inline: true,
+        unused: true,
+    }
+    input: {
+        (function f(a) {
+            (function(b = console.log("FAIL")) {})(a);
+        })(42);
+        console.log(typeof b);
+    }
+    expect: {
+        (function(a) {
+            [ b = console.log("FAIL") ] = [ a ],
+            void 0;
+            var b;
+        })(42);
+        console.log(typeof b);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+issue_5057_3: {
+    options = {
+        inline: 3,
+        unused: true,
+    }
+    input: {
+        (function(a) {
+            (function f(b) {
+                (function(a = console.log("FAIL 1")) {})(b);
+                console.log(a);
+            })("FAIL 2");
+        })("PASS");
+    }
+    expect: {
+        (function(a) {
+            (function(b) {
+                (function(a = console.log("FAIL 1")) {})(b);
+                console.log(a);
+            })("FAIL 2");
+        })("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5057_4: {
+    options = {
+        if_return: true,
+        inline: true,
+        unused: true,
+    }
+    input: {
+        (function(a) {
+            (function f(b) {
+                (function(a = console.log("FAIL 1")) {})(b);
+                console.log(a);
+            })("FAIL 2");
+        })("PASS");
+    }
+    expect: {
+        (function(a) {
+            var b = "FAIL 2";
+            (function(a = console.log("FAIL 1")) {})(b);
+            console.log(a);
+        })("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5065: {
+    options = {
+        pure_getters: "strict",
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var [ a = console.log("PASS") ] = [ (A = 42).p ];
+    }
+    expect: {
+        var [ a = console.log("PASS") ] = [ (A = 42).p ];
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5138_1: {
+    options = {
+        evaluate: true,
+    }
+    input: {
+        console.log(function(a, b = a = "FAIL") {
+            return a;
+        }() && "PASS");
+    }
+    expect: {
+        console.log(function(a, b = a = "FAIL") {
+            return a;
+        }() && "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5138_2: {
+    options = {
+        evaluate: true,
+    }
+    input: {
+        console.log(function(a, b = a = "FAIL 1") {
+            return a;
+        }(null, "FAIL 2") || "PASS");
+    }
+    expect: {
+        console.log((null, "PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5192: {
+    options = {
+        dead_code: true,
+        ie: true,
+    }
+    input: {
+        (function a(a,  [] = a = "PASS") {
+            console.log(a);
+        })("FAIL");
+    }
+    expect: {
+        (function a(a,  [] = a = "PASS") {
+            console.log(a);
+        })("FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5246_1: {
+    options = {
+        pure_getters: true,
+        unused: true,
+    }
+    input: {
+        console.log(function({} = 42) {
+            return "PASS";
+        }("foo"));
+    }
+    expect: {
+        console.log(function({} = 0) {
+            return "PASS";
+        }("foo"));
+    }
+    expect_stdout: "PASS"
+    expect_warnings: [
+        "INFO: Dropping unused default argument value {}=42 [test/compress/default-values.js:1,29]",
+        "INFO: Dropping unused default argument value {}=0 [test/compress/default-values.js:1,29]",
+    ]
+    node_version: ">=6"
+}
+
+issue_5246_2: {
+    options = {
+        unused: true,
+    }
+    input: {
+        (function f(a = "FAIL", [] = 42) {
+            console.log(a);
+        })("PASS", []);
+    }
+    expect: {
+        (function(a = "FAIL", []) {
+            console.log(a);
+        })("PASS", []);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5246_3: {
+    options = {
+        default_values: true,
+        unused: true,
+    }
+    input: {
+        console.log(function f([ , {} ] = null){}([ , {} ]));
+    }
+    expect: {
+        console.log(function([ {} ]){}([ {} ]));
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+issue_5256: {
+    options = {
+        inline: true,
+    }
+    input: {
+        (function(arguments = console.log) {
+            console;
+        })();
+        console.log(typeof arguments);
+    }
+    expect: {
+        // Syntax error on Node.js v6
+        (function(arguments = console.log) {
+            console;
+        })();
+        console.log(typeof arguments);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=8"
+}
--- a/test/compress/destructured.js
+++ b/test/compress/destructured.js
@@ -220,7 +220,7 @@ funarg_side_effects_2: {
        }
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.2"
 }

 funarg_side_effects_3: {
@@ -254,7 +254,7 @@ funarg_side_effects_3: {
        }
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.2"
 }

 funarg_unused_1: {
@@ -395,7 +395,8 @@ funarg_unused_6_keep_fargs: {
    }
    expect: {
        (function() {
-            var {} = (console, 42);
+            console;
+            var {} = 42;
        })();
        console.log(typeof a);
    }
@@ -1010,6 +1011,42 @@ collapse_vars_8: {
    node_version: ">=6"
 }

+collapse_vars_9: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        console.log(function(a) {
+            try {
+                var b = function([ c ]) {
+                    if (c)
+                        return "FAIL 1";
+                }();
+                a = "FAIL 2";
+                return b;
+            } catch (e) {
+                return a;
+            }
+        }("PASS"));
+    }
+    expect: {
+        console.log(function(a) {
+            try {
+                var b = function([ c ]) {
+                    if (c)
+                        return "FAIL 1";
+                }();
+                a = "FAIL 2";
+                return b;
+            } catch (e) {
+                return a;
+            }
+        }("PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 conditionals: {
    options = {
        conditionals: true,
@@ -1069,7 +1106,7 @@ drop_unused_1: {
            try {
                throw 42;
            } catch (a) {
-                var [ a ] = [];
+                var a = [][0];
            }
        }
    }
@@ -1102,6 +1139,175 @@ drop_unused_2: {
    node_version: ">=6"
 }

+drop_hole: {
+    options = {
+        unused: true,
+    }
+    input: {
+        var [ a ] = [ , ];
+        console.log(a);
+    }
+    expect: {
+        var a = [][0];
+        console.log(a);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+keep_key_1: {
+    options = {
+        evaluate: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        ({} = {
+            [(console.log("PASS"), 42)]: null,
+        });
+    }
+    expect: {
+        ({} = {
+            [(console.log("PASS"), 42)]: 0,
+        });
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+keep_key_2: {
+    options = {
+        evaluate: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var { 42: a } = { [(console.log("PASS"), 42)](){} };
+    }
+    expect: {
+        var {} = { [(console.log("PASS"), 42)]: 0 };
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+keep_key_2_pure_getters: {
+    options = {
+        evaluate: true,
+        pure_getters: "strict",
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var { 42: a } = { [(console.log("PASS"), 42)](){} };
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+keep_reference: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = [ {}, 42 ];
+        var [ b, c ] = a;
+        console.log(a[0] === b ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = [ {}, 42 ];
+        var [ b ] = a;
+        console.log(a[0] === b ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+maintain_position_assign: {
+    options = {
+        unused: true,
+    }
+    input: {
+        console.log(([ , ] = [ , "PASS" ])[1]);
+    }
+    expect: {
+        console.log([ , "PASS" ][1]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+maintain_position_var: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        A = "FAIL";
+        var [ a, b ] = [ A ];
+        console.log(b || "PASS");
+    }
+    expect: {
+        A = "FAIL";
+        var [ , b ] = [ A ];
+        console.log(b || "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+side_effects_array: {
+    options = {
+        unused: true,
+    }
+    input: {
+        try {
+            var [ a ] = 42;
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            var [ a ] = 42;
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+side_effects_object: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = null, b = console, { c } = 42;
+        try {
+            c[a = "PASS"];
+        } catch (e) {
+            console.log(a);
+        }
+    }
+    expect: {
+        var a = null, c = (console, 42["c"]);
+        try {
+            c[a = "PASS"];
+        } catch (e) {
+            console.log(a);
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 join_vars: {
    options = {
        conditionals: true,
@@ -1376,6 +1582,75 @@ hoist_vars: {
    node_version: ">=6"
 }

+singleton_1: {
+    options = {
+        pure_getters: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var [ a ] = "P", b, o = {};
+        [ { 1: o.p } ] = [ "FAIL" ];
+        ({ foo: [ o.q ] } = { foo: "S" });
+        [ b = "S" ] = [];
+        console.log(a + o.p + o.q + b);
+    }
+    expect: {
+        var b, a = "P"[0], o = {};
+        o.p = [ "FAIL"["1"] ][0];
+        o.q = { foo: "S"[0] }["foo"];
+        [ b = "S" ] = [];
+        console.log(a + o.p + o.q + b);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+singleton_2: {
+    options = {
+        evaluate: true,
+        passes: 2,
+        pure_getters: true,
+        side_effects: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var [ a ] = "P", b, o = {};
+        [ { 1: o.p } ] = [ "FAIL" ];
+        ({ foo: [ o.q ] } = { foo: "S" });
+        [ b = "S" ] = [];
+        console.log(a + o.p + o.q + b);
+    }
+    expect: {
+        var b, a = "P", o = {};
+        o.p = "A";
+        o.q = "S";
+        [ b = "S" ] = [];
+        console.log(a + o.p + o.q + b);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+singleton_side_effects: {
+    options = {
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        [ 42[console.log("foo")] ] = [ console.log("bar") ];
+    }
+    expect: {
+        [ 42[console.log("foo")] ] = [ console.log("bar") ];
+    }
+    expect_stdout: [
+        "bar",
+        "foo",
+    ]
+    node_version: ">=6"
+}
+
 issue_4280: {
    options = {
        evaluate: true,
@@ -1570,13 +1845,13 @@ issue_4294: {
    expect: {
        A = "PASS";
        (function() {
-            var b = function({
-                [b]: {},
+            var a = function({
+                [a]: {},
            }) {}({
-                [b]: 0,
+                [a]: 0,
            });
-            var b = A;
-            console.log(b);
+            var a = A;
+            console.log(a);
        })();
    }
    expect_stdout: "PASS"
@@ -1795,7 +2070,7 @@ issue_4319: {

 issue_4321: {
    options = {
-        inline: true,
+        inline: 3,
        keep_fargs: false,
    }
    input: {
@@ -1824,7 +2099,7 @@ issue_4321: {

 issue_4323: {
    options = {
-        ie8: true,
+        ie: true,
        inline: true,
        merge_vars: true,
        reduce_vars: true,
@@ -1922,7 +2197,7 @@ issue_4372_2: {
    }
    expect: {
        var a;
-        [ a ] = [ "PASS", "FAIL" ];
+        [ a ] = a = [ "PASS", "FAIL" ];
        console.log(a);
    }
    expect_stdout: "PASS"
@@ -2556,3 +2831,598 @@ issue_4608_2: {
    expect_stdout: "f"
    node_version: ">=6"
 }
+
+issue_4994: {
+    options = {
+        loops: true,
+        unused: true,
+    }
+    input: {
+        var a = "FAIL";
+        (function([
+            {
+                [function() {
+                    for (a in { PASS: null });
+                }()]: b,
+            },
+        ]) {
+            var a;
+        })([ 42 ]);
+        console.log(a);
+    }
+    expect: {
+        var a = "FAIL";
+        (function([
+            {
+                [function() {
+                    for (a in { PASS: null });
+                }()]: b,
+            },
+        ]) {})([ 42 ]);
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5017: {
+    options = {
+        collapse_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = function() {};
+        var b = c = a;
+        var c = [ c ] = [ c ];
+        console.log(c[0] === a ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = function() {};
+        var b = a;
+        var c = [ c ] = [ c = a ];
+        console.log(c[0] === a ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5071_1: {
+    options = {
+        unused: true,
+    }
+    input: {
+        var a;
+        console.log(([ , a ] = [ "PA", , ]).join("SS"));
+    }
+    expect: {
+        var a;
+        console.log(([ , a ] = [ "PA", , ]).join("SS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5071_2: {
+    options = {
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        var a;
+        ([ a ] = []).p = console.log("PASS");
+    }
+    expect: {
+        var a;
+        ([ a ] = []).p = console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5074_getter: {
+    options = {
+        evaluate: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        ({} = { get [(console.log("PASS"), 42)]() {} });
+    }
+    expect: {
+        ({} = { [(console.log("PASS"), 42)]: 0 });
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5074_getter_pure_getters: {
+    options = {
+        evaluate: true,
+        pure_getters: "strict",
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        ({} = { get [(console.log("PASS"), 42)]() {} });
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5074_setter: {
+    options = {
+        evaluate: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        ({} = { set [(console.log("PASS"), 42)](v) {} });
+    }
+    expect: {
+        ({} = { [(console.log("PASS"), 42)]: 0 });
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5074_setter_pure_getters: {
+    options = {
+        evaluate: true,
+        pure_getters: "strict",
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        ({} = { set [(console.log("PASS"), 42)](v) {} });
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5074_method: {
+    options = {
+        evaluate: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        ({} = { [(console.log("PASS"), 42)]() {} });
+    }
+    expect: {
+        ({} = { [(console.log("PASS"), 42)]: 0 });
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5074_method_pure_getters: {
+    options = {
+        evaluate: true,
+        pure_getters: "strict",
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        ({} = { [(console.log("PASS"), 42)]() {} });
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5085_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        var [ b ] = [ 42, a ], c = b ? 0 : a = "FAIL";
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS";
+        var b = [ 42 ][0];
+        b;
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5085_2: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        side_effects: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        (function(b) {
+            [ b ] = [ 42, a ];
+            var c = b ? 0 : a = "FAIL";
+        })();
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS";
+        (function(b) {
+            b = [ 42 ][0];
+        })();
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5087_1: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        properties: true,
+        sequences: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        (function() {
+            (function() {
+                (function([ b ]) {
+                    b && console.log(b);
+                })([ a ]);
+            })();
+        })();
+    }
+    expect: {
+        var a = "PASS";
+        (function() {
+            var b;
+            (b = a) && console.log(b);
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5087_2: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        passes: 2,
+        properties: true,
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        (function() {
+            (function() {
+                (function([ b ]) {
+                    b && console.log(b);
+                })([ a ]);
+            })();
+        })();
+    }
+    expect: {
+        var a = "PASS";
+        a && console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5114_1: {
+    options = {
+        inline: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        (function({}, a) {})(42);
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS";
+        [ {} ] = [ 42 ],
+        void 0;
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5114_2: {
+    options = {
+        inline: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        (function f([], a) {
+            f.length;
+        })([]);
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS";
+        0;
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5114_3: {
+    options = {
+        inline: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        (function f(a, {}) {
+            f.length;
+        })(null, 42);
+        console.log(a);
+    }
+    expect: {
+        var a = "PASS";
+        0;
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5153_array_assign: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        var a = function*() {
+            yield b;
+        }(), b;
+        [ b ] = b = a;
+        console.log(a === b ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = function*() {
+            yield b;
+        }(), b;
+        [ b ] = b = a;
+        console.log(a === b ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5153_array_var: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        var a = function*() {
+            yield b;
+        }(), [ b ] = b = a;
+        console.log(a === b ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = function*() {
+            yield b;
+        }(), [ b ] = b = a;
+        console.log(a === b ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5153_object_assign: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        var a = {
+            get p() {
+                return b;
+            },
+        }, b;
+        ({
+            p: b
+        } = b = a);
+        console.log(a === b ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = {
+            get p() {
+                return b;
+            },
+        }, b;
+        ({
+            p: b
+        } = b = a);
+        console.log(a === b ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5153_object_var: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        var a = {
+            get p() {
+                return b;
+            },
+        }, {
+            p: b
+        } = b = a;
+        console.log(a === b ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = {
+            get p() {
+                return b;
+            },
+        }, {
+            p: b
+        } = b = a;
+        console.log(a === b ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5168: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        (function a({
+            [console.log(typeof function() {
+                ++a;
+                return a;
+            }())]: b,
+        }) {
+            var a;
+        })({});
+    }
+    expect: {
+        (function a({
+            [console.log(typeof function() {
+                ++a;
+                return a;
+            }())]: b,
+        }) {
+            var a;
+        })({});
+    }
+    expect_stdout: "function"
+    node_version: ">=6"
+}
+
+issue_5189_1: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = 42;
+        [ a.p ] = a = "PASS";
+        console.log(a);
+    }
+    expect: {
+        var a;
+        [ a.p ] = a = "PASS";
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5189_2: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = 42;
+        ({ p: a.q } = a = "PASS");
+        console.log(a);
+    }
+    expect: {
+        var a;
+        ({ p: a.q } = a = "PASS");
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5222: {
+    options = {
+        hoist_props: true,
+        inline: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            do {
+                (function() {
+                    var a = {
+                        p: [ a ] = [],
+                    };
+                })();
+            } while (console.log("PASS"));
+        }
+        f();
+    }
+    expect: {
+        do {
+            a = void 0,
+            a = {
+                p: [ a ] = [],
+            };
+        } while (console.log("PASS"));
+        var a;
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5288: {
+    options = {
+        conditionals: true,
+        inline: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+        varify: true,
+    }
+    input: {
+        while (function([]) {}([ function f() {
+            if (console)
+                return console.log("PASS");
+            else {
+                let a = 0;
+            }
+        }() ]));
+    }
+    expect: {
+        while ([ [ console ? console.log("PASS") : 0 ] ], void 0);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -795,9 +795,9 @@ issue_1656: {
        beautify: true,
    }
    input: {
-        for(var a=0;;);
+        for (var a=0;;);
    }
-    expect_exact: "for (;;) ;"
+    expect_exact: "for (;;);"
 }

 issue_1709: {
@@ -1110,7 +1110,7 @@ issue_1838: {
    }
    expect_exact: [
        "function f() {",
-        "    for (a; c; ) ;",
+        "    for (a; c; );",
        "}",
    ]
 }
@@ -1233,8 +1233,11 @@ issue_2105_2: {
 issue_2105_3: {
    options = {
        inline: true,
-        passes: 2,
+        join_vars: true,
+        passes: 3,
        reduce_vars: true,
+        side_effects: true,
+        sequences: true,
        unused: true,
    }
    input: {
@@ -1258,12 +1261,12 @@ issue_2105_3: {
        });
    }
    expect: {
-        !void void {
+        ({
            prop: function() {
-                console.log;
-                void console.log("PASS");
-            }
-        }.prop();
+                console.log,
+                console.log("PASS");
+            },
+        }).prop();
    }
    expect_stdout: "PASS"
 }
@@ -1557,9 +1560,9 @@ issue_2665: {
    }
    expect: {
        var a = 1;
-        !function g() {
+        (function g() {
            a-- && g();
-        }();
+        })();
        console.log(a);
    }
    expect_stdout: "-1"
@@ -1728,7 +1731,8 @@ issue_2768: {
    }
    expect: {
        var a = "FAIL";
-        var c = (d = a, void (d && (a = "PASS")));
+        d = a;
+        var c = void (d && (a = "PASS"));
        var d;
        console.log(a, typeof c);
    }
@@ -1765,7 +1769,7 @@ issue_2846: {
 issue_805_1: {
    options = {
        inline: true,
-        passes: 2,
+        passes: 3,
        pure_getters: "strict",
        reduce_vars: true,
        sequences: true,
@@ -1798,7 +1802,7 @@ issue_805_1: {
 issue_805_2: {
    options = {
        inline: true,
-        passes: 2,
+        passes: 3,
        pure_getters: "strict",
        reduce_vars: true,
        sequences: true,
@@ -2345,7 +2349,7 @@ function_argument_reference: {

 function_parameter_ie8: {
    options = {
-        ie8: true,
+        ie: true,
        reduce_vars: true,
        unused: true,
    }
@@ -2371,6 +2375,7 @@ function_parameter_ie8: {
 issue_3664: {
    options = {
        pure_getters: "strict",
+        side_effects: true,
        unused: true,
    }
    input: {
@@ -2381,7 +2386,8 @@ issue_3664: {
    }
    expect: {
        console.log(function() {
-            var b = ([ b && console.log("FAIL") ].p = 0, 0);
+            a = (a = [ b && console.log("FAIL") ]).p = 0;
+            var a, b = 0;
            return "PASS";
        }());
    }
@@ -2391,6 +2397,7 @@ issue_3664: {
 issue_3673: {
    options = {
        pure_getters: "strict",
+        sequences: true,
        side_effects: true,
        toplevel: true,
        unused: true,
@@ -2401,8 +2408,6 @@ issue_3673: {
        console.log("PASS");
    }
    expect: {
-        var a;
-        (a = [ a ]).p = 42;
        console.log("PASS");
    }
    expect_stdout: "PASS"
@@ -2551,10 +2556,9 @@ issue_3899: {
        console.log(typeof a);
    }
    expect: {
-        function a() {
+        console.log(typeof function() {
            return 2;
-        }
-        console.log(typeof a);
+        });
    }
    expect_stdout: "function"
 }
@@ -2916,7 +2920,7 @@ issue_4133: {
        console.log(a);
    }
    expect: {
-        var b = 1;
+        var a = 1;
        console.log(0);
    }
    expect_stdout: "0"
@@ -3062,7 +3066,7 @@ issue_4184: {
    expect_stdout: "42"
 }

-issue_4235: {
+issue_4235_1: {
    options = {
        inline: true,
        reduce_vars: true,
@@ -3080,12 +3084,35 @@ issue_4235: {
        })();
    }
    expect: {
+        void function() {
+            var f = console.log(f);
+        }();
+    }
+    expect_stdout: "undefined"
+}
+
+issue_4235_2: {
+    options = {
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+        varify: true,
+    }
+    input: {
        (function() {
-            f = console.log(f),
-            void 0;
-            var f;
+            {
+                const f = 0;
+            }
+            (function f() {
+                var f = console.log(f);
+            })();
        })();
    }
+    expect: {
+        console.log(void 0);
+    }
    expect_stdout: "undefined"
 }

@@ -3231,7 +3258,7 @@ issue_4558_1: {
 issue_4558_2: {
    options = {
        evaluate: true,
-        ie8: true,
+        ie: true,
        reduce_vars: true,
        unused: true,
    }
@@ -3357,3 +3384,209 @@ issue_4806_3: {
    }
    expect_stdout: "PASS"
 }
+
+issue_4834: {
+    options = {
+        inline: true,
+        keep_fargs: false,
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        try {
+            new function(a, b) {
+                b;
+                b.p;
+            }(42);
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            b.p;
+        } catch (e) {
+            console.log("PASS");
+        }
+        var b;
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4912_1: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = A = function() {};
+        A;
+        a.prototype = {
+            f: function() {
+                console.log("PASS");
+            },
+        };
+        new A().f();
+    }
+    expect: {
+        var a = A = function() {};
+        A;
+        a.prototype = {
+            f: function() {
+                console.log("PASS");
+            },
+        };
+        new A().f();
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4912_2: {
+    options = {
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var g, f = function() {};
+            f.p = {};
+            (g = f.p.q = function() {}).r = "PASS";
+            return f;
+        }().p.q.r);
+    }
+    expect: {
+        console.log(function() {
+            var g, f = function() {};
+            f.p = {};
+            (f.p.q = function() {}).r = "PASS";
+            return f;
+        }().p.q.r);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4912_3: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(f, g) {
+            f = function() {};
+            f.p = {};
+            g = f.p.q = function() {};
+            g.r = "PASS";
+            return f;
+        }().p.q.r);
+    }
+    expect: {
+        console.log(function(f, g) {
+            f = function() {};
+            f.p = {};
+            g = f.p.q = function() {};
+            g.r = "PASS";
+            return f;
+        }().p.q.r);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5079: {
+    options = {
+        collapse_vars: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        do {
+            (a = 123456).p = a;
+            a.q = null;
+        } while (console.log("PASS"));
+    }
+    expect: {
+        do {
+            0, 0, null;
+        } while (console.log("PASS"));
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5224: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            try {
+                var b = function() {
+                    var a = "FAIL 1";
+                    null && a;
+                    a = console.log(a);
+                }(new function(c, d) {
+                    console.log(d);
+                    a;
+                }("FAIL 2", Infinity));
+            } finally {
+                return f;
+            }
+        }
+        f();
+    }
+    expect: {
+        (function f() {
+            try {
+                (function() {
+                    var a = "FAIL 1";
+                    null;
+                    a = console.log(a);
+                })(function() {
+                    console.log(1 / 0);
+                    a;
+                }());
+            } finally {
+                return f;
+            }
+        })();
+    }
+    expect_stdout: "Infinity"
+}
+
+issue_5271: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            do {
+                var a = b = 0 ^ f, b = b;
+            } while (console.log(42 - b));
+        }
+        f();
+    }
+    expect: {
+        (function f() {
+            do {
+                var b;
+                b = 0 ^ f;
+            } while (console.log(42 - b));
+        })();
+    }
+    expect_stdout: "42"
+}
--- a/test/compress/evaluate.js
+++ b/test/compress/evaluate.js
@@ -684,26 +684,47 @@ prototype_function: {
        side_effects: true,
    }
    input: {
-        var a = ({valueOf: 0}) < 1;
-        var b = ({toString: 0}) < 1;
-        var c = ({valueOf: 0}) + "";
-        var d = ({toString: 0}) + "";
-        var e = (({valueOf: 0}) + "")[2];
-        var f = (({toString: 0}) + "")[2];
-        var g = ({valueOf: 0}).valueOf();
-        var h = ({toString: 0}).toString();
+        function v() {
+            return this.valueOf === v ? "PASS" : "FAIL";
+        }
+        console.log(({ valueOf: v }) < 1);
+        console.log(({ valueOf: v }) + "");
+        console.log((( {valueOf: v }) + "")[2]);
+        console.log(({ valueOf: v }).valueOf());
+        function t() {
+            return this.toString === t ? "PASS" : "FAIL";
+        }
+        console.log(({ toString: t }) < 1);
+        console.log(({ toString: t }) + "");
+        console.log((( {toString: t }) + "")[2]);
+        console.log(({ toString: t }).toString());
    }
    expect: {
-        var a = ({valueOf: 0}) < 1;
-        var b = ({toString: 0}) < 1;
-        var c = ({valueOf: 0}) + "";
-        var d = ({toString: 0}) + "";
-        var e = (({valueOf: 0}) + "")[2];
-        var f = (({toString: 0}) + "")[2];
-        var g = 0();
-        var h = 0();
+        function v() {
+            return this.valueOf === v ? "PASS" : "FAIL";
+        }
+        console.log(({ valueOf: v }) < 1);
+        console.log(({ valueOf: v }) + "");
+        console.log((( {valueOf: v }) + "")[2]);
+        console.log(({ valueOf: v }).valueOf());
+        function t() {
+            return this.toString === t ? "PASS" : "FAIL";
+        }
+        console.log(({ toString: t }) < 1);
+        console.log(({ toString: t }) + "");
+        console.log((( {toString: t }) + "")[2]);
+        console.log(({ toString: t }).toString());
    }
-    expect_stdout: true
+    expect_stdout: [
+        "false",
+        "PASS",
+        "S",
+        "PASS",
+        "false",
+        "PASS",
+        "S",
+        "PASS",
+    ]
 }

 call_args: {
@@ -2731,8 +2752,7 @@ issue_3944: {
    }
    expect: {
        void function f() {
-            while (a = 0 == (a = void 0), console.log(a), void 0);
-            var a;
+            while (0 == void 0, console.log(false), void 0);
            f;
        }();
    }
@@ -3181,3 +3201,43 @@ issue_4552: {
    }
    expect_stdout: "NaN"
 }
+
+issue_4886_1: {
+    options = {
+        evaluate: true,
+        unsafe: true,
+    }
+    input: {
+        console.log("length" in {
+            __proto__: function() {},
+            length: void 0,
+        });
+    }
+    expect: {
+        console.log("length" in {
+            __proto__: function() {},
+            length: void 0,
+        });
+    }
+    expect_stdout: "true"
+}
+
+issue_4886_2: {
+    options = {
+        evaluate: true,
+        unsafe: true,
+    }
+    input: {
+        console.log("foo" in {
+            "foo": null,
+            __proto__: 42,
+        });
+    }
+    expect: {
+        console.log("foo" in {
+            "foo": null,
+            __proto__: 42,
+        });
+    }
+    expect_stdout: "true"
+}
--- a/test/compress/exponentiation.js
+++ b/test/compress/exponentiation.js
@@ -62,7 +62,7 @@ assignment_2: {
    }
    expect_exact: "var a=8n;a**=a;console.log(a);"
    expect_stdout: "16777216n"
-    node_version: ">=10"
+    node_version: ">=10.4.0"
 }

 evaluate: {
@@ -100,7 +100,7 @@ issue_4664: {
        (function f() {
            new function(a) {
                console.log(typeof f, 2 ** 30, typeof this);
-            }(0, A = 0);
+            }(A = 0);
        })();
    }
    expect_stdout: "function 1073741824 object"
--- a/test/compress/exports.js
+++ b/test/compress/exports.js
@@ -91,6 +91,13 @@ defaults_parentheses_6: {
    expect_exact: 'export default(function(){while(!console);})()?"FAIL":"PASS";'
 }

+defaults_regexp: {
+    input: {
+        export default /foo/;
+    }
+    expect_exact: "export default/foo/;"
+}
+
 foreign: {
    input: {
        export * from "foo";
@@ -242,7 +249,7 @@ hoist_exports_2: {
        }
    }
    expect: {
-        let e, { foo: a } = 42;
+        let e, a = 42["foo"];
        function f(t, { [e]: o }) {
            t(o, f);
        }
--- a/test/compress/functions.js
+++ b/test/compress/functions.js
--- a/test/compress/hoist_props.js
+++ b/test/compress/hoist_props.js
@@ -217,7 +217,8 @@ name_collision_1: {
        var obj_foo = 1;
        var obj_bar = 2;
        function f() {
-            var obj_foo$0 = 3,
+            var obj,
+                obj_foo$0 = 3,
                obj_bar = 4,
                obj_b_r = 5,
                obj_b_r$0 = 6,
@@ -249,7 +250,8 @@ name_collision_2: {
        console.log(o.p === o.p, o["+"](4), o["-"](5), o__$0, o__$1);
    }
    expect: {
-        var o_p = 1,
+        var o,
+            o_p = 1,
            o__ = function(x) {
                return x;
            },
@@ -283,7 +285,8 @@ name_collision_3: {
        console.log(o.p === o.p, o["+"](4), o["-"](5));
    }
    expect: {
-        var o_p = 1,
+        var o,
+            o_p = 1,
            o__ = function(x) {
                return x;
            },
@@ -315,7 +318,7 @@ name_collision_4: {
    }
    expect: {
        console.log(function() {
-            var o_p$0 = 0, o_q = "PASS";
+            var o, o_p$0 = 0, o_q = "PASS";
            return function(o_p) {
                if (!o_p$0) return o_p;
            }(o_q);
@@ -768,7 +771,7 @@ issue_3046: {
    expect: {
        console.log(function(a) {
            do {
-                var b_c = a++;
+                var b, b_c = a++;
            } while (b_c && a);
            return a;
        }(0));
@@ -777,6 +780,32 @@ issue_3046: {
 }

 issue_3071_1: {
+    options = {
+        evaluate: true,
+        hoist_props: true,
+        inline: true,
+        join_vars: true,
+        passes: 3,
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        (function() {
+            var obj = {};
+            obj.one = 1;
+            obj.two = 2;
+            console.log(obj.one, obj.two);
+        })();
+    }
+    expect: {
+        console.log(1, 2);
+    }
+    expect_stdout: "1 2"
+}
+
+issue_3071_1_toplevel: {
    options = {
        evaluate: true,
        hoist_props: true,
@@ -905,7 +934,7 @@ issue_3411: {
    expect: {
        var c = 1;
        !function f() {
-            var o_p = --c && f();
+            var o, o_p = --c && f();
            +{} || console.log("PASS");
        }();
    }
@@ -1016,9 +1045,7 @@ issue_3945_1: {
    expect: {
        function f() {
            o.p;
-            var o = {
-                q: 0,
-            };
+            var o, o_q = 0;
        }
    }
 }
@@ -1037,9 +1064,7 @@ issue_3945_2: {
    }
    expect: {
        console.log(typeof o);
-        var o = {
-            p: 0,
-        };
+        var o, o_p = 0;
    }
    expect_stdout: "undefined"
 }
@@ -1094,3 +1119,60 @@ object_super: {
    expect_stdout: "PASS"
    node_version: ">=4"
 }
+
+issue_4985: {
+    options = {
+        hoist_props: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = { p: 42 };
+        console.log(function() {
+            a;
+        }());
+    }
+    expect: {
+        var a, a_p = 42;
+        console.log(function() {
+            ({});
+        }());
+    }
+    expect_stdout: "undefined"
+}
+
+issue_5182: {
+    options = {
+        hoist_props: true,
+        merge_vars: true,
+        passes: 2,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var o = console;
+        log = o.log;
+        o = {
+            p: function(a) {
+                console.log(a ? "PASS" : "FAIL");
+                return a;
+            },
+        };
+        log(o.p(42));
+    }
+    expect: {
+        var o = console;
+        log = o.log;
+        o = function(a) {
+            console.log(a ? "PASS" : "FAIL");
+            return a;
+        };
+        log(o(42));
+    }
+    expect_stdout: [
+        "PASS",
+        "42",
+    ]
+}
--- a/test/compress/hoist_vars.js
+++ b/test/compress/hoist_vars.js
@@ -135,7 +135,31 @@ issue_2295: {
    }
 }

-issue_4487: {
+issue_4487_1: {
+    options = {
+        functions: true,
+        hoist_vars: true,
+        keep_fnames: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = function f() {
+            var f = console.log(typeof f);
+        };
+        var b = a();
+    }
+    expect: {
+        var a = function f() {
+            var f = console.log(typeof f);
+        };
+        a();
+    }
+    expect_stdout: "undefined"
+}
+
+issue_4487_2: {
    options = {
        functions: true,
        hoist_vars: true,
@@ -160,6 +184,30 @@ issue_4487: {
    expect_stdout: "undefined"
 }

+issue_4487_3: {
+    options = {
+        functions: true,
+        hoist_vars: true,
+        keep_fnames: true,
+        passes: 3,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = function f() {
+            var f = console.log(typeof f);
+        };
+        var b = a();
+    }
+    expect: {
+        (function a() {
+            console.log(typeof void 0);
+        })();
+    }
+    expect_stdout: "undefined"
+}
+
 issue_4489: {
    options = {
        collapse_vars: true,
@@ -234,9 +282,221 @@ issue_4736: {
        (function() {
            (function() {
                0,
-                console.log(1073741824);
+                console.log(1 << 30);
            })();
        })();
    }
    expect_stdout: "1073741824"
 }
+
+issue_4839: {
+    options = {
+        evaluate: true,
+        hoist_vars: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var log = console.log, o = function(a, b) {
+            return b && b;
+        }("foo");
+        for (var k in o)
+            throw "FAIL";
+        log("PASS");
+    }
+    expect: {
+        var k, log = console.log;
+        for (k in void 0)
+            throw "FAIL";
+        log("PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4859: {
+    options = {
+        evaluate: true,
+        hoist_vars: true,
+        keep_infinity: true,
+        merge_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f(a) {
+            var b = (a = 2, 1 / 0), c = 3;
+            var d = a + b;
+            console.log(d);
+            return f;
+        }
+        f();
+    }
+    expect: {
+        (function f(a) {
+            console.log(2 + 1 / 0);
+            return f;
+        })();
+    }
+    expect_stdout: "Infinity"
+}
+
+issue_4893_1: {
+    options = {
+        collapse_vars: true,
+        evaluate: true,
+        hoist_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            function g() {}
+            var a = null;
+            var b = null;
+            var c = null;
+            b.p += a = 42;
+            f;
+        }
+        try {
+            f();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try{
+            (function f() {
+                null.p += 42;
+                f;
+            })();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4893_2: {
+    options = {
+        collapse_vars: true,
+        hoist_vars: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            function g() {}
+            var a = null;
+            var b = null;
+            var c = null;
+            b.p += a = 42;
+            f;
+        }
+        try {
+            f();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try{
+            (function() {
+                var b;
+                b = null;
+                b.p += 42;
+            })();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4898: {
+    options = {
+        collapse_vars: true,
+        evaluate: true,
+        hoist_vars: true,
+        loops: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        do {
+            var b = [ console.log("PASS") ];
+            var c = b;
+        } while (c.p = 0);
+    }
+    expect: {
+        var b;
+        b = [ console.log("PASS") ];
+        b.p = 0;
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5187: {
+    options = {
+        hoist_props: true,
+        hoist_vars: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var a = 42;
+            do {
+                var b = { 0: a++ };
+            } while (console.log(b[b ^= 0]));
+        }
+        f();
+    }
+    expect: {
+        (function() {
+            var b, a = 42;
+            do {
+                b = { 0: a++ };
+            } while (console.log(b[b ^= 0]));
+        })();
+    }
+    expect_stdout: "42"
+}
+
+issue_5195: {
+    options = {
+        hoist_props: true,
+        hoist_vars: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var a;
+            do {
+                var b = { p: a };
+            } while (console.log(b += ""));
+        }
+        f();
+    }
+    expect: {
+        (function() {
+            var a, b;
+            do {
+                b = { p: a };
+            } while (console.log(b += ""));
+        })();
+    }
+    expect_stdout: "[object Object]"
+}
--- a/test/compress/ie8.js
+++ b/test/compress/ie8.js
--- a/test/compress/if_return.js
+++ b/test/compress/if_return.js
@@ -545,7 +545,36 @@ if_body_return_3: {
    ]
 }

-issue_3600: {
+issue_3600_1: {
+    options = {
+        if_return: true,
+        inline: 3,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var c = 0;
+        (function() {
+            if ([ ][c++]); else return;
+            return void function() {
+                var b = --b, a = c = 42;
+                return c;
+            }();
+        })();
+        console.log(c);
+    }
+    expect: {
+        var c = 0;
+        (function() {
+            if ([][c++]) b = --b, c = 42;
+            var b;
+        })();
+        console.log(c);
+    }
+    expect_stdout: "1"
+}
+
+issue_3600_2: {
    options = {
        if_return: true,
        inline: true,
@@ -566,7 +595,9 @@ issue_3600: {
    expect: {
        var c = 0;
        (function() {
-            if ([][c++]) b = --b, c = 42;
+            if ([][c++])
+                b = --b,
+                c = 42;
            var b;
        })();
        console.log(c);
--- a/test/compress/imports.js
+++ b/test/compress/imports.js
@@ -54,13 +54,22 @@ dynamic_nought: {
    expect_exact: "import(foo);"
 }

-import_meta: {
+import_meta_1: {
    input: {
        console.log(import.meta, import.meta.url);
    }
    expect_exact: "console.log(import.meta,import.meta.url);"
 }

+import_meta_2: {
+    input: {
+        import.meta.url.split("/").forEach(function(part, index) {
+            console.log(index, part);
+        });
+    }
+    expect_exact: 'import.meta.url.split("/").forEach(function(part,index){console.log(index,part)});'
+}
+
 same_quotes: {
    beautify = {
        beautify: true,
@@ -85,13 +94,31 @@ drop_unused: {
    }
    input: {
        import a, * as b from "foo";
-        import { c, bar as d } from "baz";
-        console.log(c);
+        import { c } from "bar";
+        import { d, _ as e } from "baz";
+        console.log(d);
    }
    expect: {
        import "foo";
-        import { c as c } from "baz";
-        console.log(c);
+        import "bar";
+        import { d as d } from "baz";
+        console.log(d);
+    }
+}
+
+drop_side_effect_free: {
+    options = {
+        imports: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        import foo from "bar";
+        var a = foo;
+    }
+    expect: {
+        import "bar";
    }
 }

--- a/test/compress/issue-1446.js
+++ b/test/compress/issue-1446.js
@@ -24,7 +24,7 @@ typeof_eq_undefined: {
 typeof_eq_undefined_ie8: {
    options = {
        comparisons: true,
-        ie8: true,
+        ie: true,
        typeofs: true,
    }
    input: {
--- a/test/compress/issue-1588.js
+++ b/test/compress/issue-1588.js
@@ -1,9 +1,9 @@
 screw_ie8: {
    options = {
-        ie8: false,
+        ie: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
    }
    input: {
        try { throw "foo"; } catch (x) { console.log(x); }
@@ -16,10 +16,10 @@ screw_ie8: {

 support_ie8: {
    options = {
-        ie8: true,
+        ie: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
    }
    input: {
        try { throw "foo"; } catch (x) { console.log(x); }
--- a/test/compress/issue-1704.js
+++ b/test/compress/issue-1704.js
@@ -1,10 +1,10 @@
 mangle_catch: {
    options = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -22,11 +22,11 @@ mangle_catch: {

 mangle_catch_ie8: {
    options = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -44,11 +44,11 @@ mangle_catch_ie8: {

 mangle_catch_var: {
    options = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -66,11 +66,11 @@ mangle_catch_var: {

 mangle_catch_var_ie8: {
    options = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -88,11 +88,11 @@ mangle_catch_var_ie8: {

 mangle_catch_toplevel: {
    options = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -110,11 +110,11 @@ mangle_catch_toplevel: {

 mangle_catch_ie8_toplevel: {
    options = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -132,11 +132,11 @@ mangle_catch_ie8_toplevel: {

 mangle_catch_var_toplevel: {
    options = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -154,11 +154,11 @@ mangle_catch_var_toplevel: {

 mangle_catch_var_ie8_toplevel: {
    options = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -176,11 +176,11 @@ mangle_catch_var_ie8_toplevel: {

 mangle_catch_redef_1: {
    options = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -198,11 +198,11 @@ mangle_catch_redef_1: {

 mangle_catch_redef_1_ie8: {
    options = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -220,11 +220,11 @@ mangle_catch_redef_1_ie8: {

 mangle_catch_redef_1_toplevel: {
    options = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -242,11 +242,11 @@ mangle_catch_redef_1_toplevel: {

 mangle_catch_redef_1_ie8_toplevel: {
    options = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -264,11 +264,11 @@ mangle_catch_redef_1_ie8_toplevel: {

 mangle_catch_redef_2: {
    options = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -285,11 +285,11 @@ mangle_catch_redef_2: {

 mangle_catch_redef_2_ie8: {
    options = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -306,11 +306,11 @@ mangle_catch_redef_2_ie8: {

 mangle_catch_redef_2_toplevel: {
    options = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -327,11 +327,11 @@ mangle_catch_redef_2_toplevel: {

 mangle_catch_redef_2_ie8_toplevel: {
    options = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -348,7 +348,7 @@ mangle_catch_redef_2_ie8_toplevel: {

 mangle_catch_redef_3: {
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -356,6 +356,7 @@ mangle_catch_redef_3: {
        try {
            throw 0;
        } catch (o) {
+            // prints "FAIL" if inlined on Node.js v4-
            (function() {
                function f() {
                    o = "FAIL";
@@ -366,12 +367,13 @@ mangle_catch_redef_3: {
        console.log(o);
    }
    expect_exact: 'var o="PASS";try{throw 0}catch(o){(function(){function c(){o="FAIL"}c(),c()})()}console.log(o);'
-    expect_stdout: true
+    expect_stdout: "PASS"
+    node_version: ">=6"
 }

 mangle_catch_redef_3_toplevel: {
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -379,6 +381,7 @@ mangle_catch_redef_3_toplevel: {
        try {
            throw 0;
        } catch (o) {
+            // prints "FAIL" if inlined on Node.js v4-
            (function() {
                function f() {
                    o = "FAIL";
@@ -389,12 +392,13 @@ mangle_catch_redef_3_toplevel: {
        console.log(o);
    }
    expect_exact: 'var c="PASS";try{throw 0}catch(c){(function(){function o(){c="FAIL"}o(),o()})()}console.log(c);'
-    expect_stdout: true
+    expect_stdout: "PASS"
+    node_version: ">=6"
 }

 mangle_catch_redef_3_ie8: {
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -402,6 +406,7 @@ mangle_catch_redef_3_ie8: {
        try {
            throw 0;
        } catch (o) {
+            // prints "FAIL" if inlined on Node.js v4-
            (function() {
                function f() {
                    o = "FAIL";
@@ -412,12 +417,13 @@ mangle_catch_redef_3_ie8: {
        console.log(o);
    }
    expect_exact: 'var o="PASS";try{throw 0}catch(o){(function(){function c(){o="FAIL"}c(),c()})()}console.log(o);'
-    expect_stdout: true
+    expect_stdout: "PASS"
+    node_version: ">=6"
 }

 mangle_catch_redef_3_ie8_toplevel: {
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -425,6 +431,7 @@ mangle_catch_redef_3_ie8_toplevel: {
        try {
            throw 0;
        } catch (o) {
+            // prints "FAIL" if inlined on Node.js v4-
            (function() {
                function f() {
                    o = "FAIL";
@@ -435,5 +442,6 @@ mangle_catch_redef_3_ie8_toplevel: {
        console.log(o);
    }
    expect_exact: 'var c="PASS";try{throw 0}catch(c){(function(){function o(){c="FAIL"}o(),o()})()}console.log(c);'
-    expect_stdout: true
+    expect_stdout: "PASS"
+    node_version: ">=6"
 }
--- a/test/compress/issue-1733.js
+++ b/test/compress/issue-1733.js
@@ -1,6 +1,6 @@
 function_iife_catch: {
    mangle = {
-        ie8: false,
+        ie: false,
    }
    input: {
        function f(n) {
@@ -21,7 +21,7 @@ function_iife_catch: {

 function_iife_catch_ie8: {
    mangle = {
-        ie8: true,
+        ie: true,
    }
    input: {
        function f(n) {
@@ -42,7 +42,7 @@ function_iife_catch_ie8: {

 function_catch_catch: {
    mangle = {
-        ie8: false,
+        ie: false,
    }
    input: {
        var o = 0;
@@ -70,7 +70,7 @@ function_catch_catch: {

 function_catch_catch_ie8: {
    mangle = {
-        ie8: true,
+        ie: true,
    }
    input: {
        var o = 0;
--- a/test/compress/issue-892.js
+++ b/test/compress/issue-892.js
@@ -1,6 +1,4 @@
 dont_mangle_arguments: {
-    mangle = {
-    };
    options = {
        booleans: true,
        comparisons: true,
@@ -21,12 +19,13 @@ dont_mangle_arguments: {
        side_effects: true,
        unused: true,
    }
+    mangle = {}
    input: {
        (function(){
            var arguments = arguments, not_arguments = 9;
            console.log(not_arguments, arguments);
-        })(5,6,7);
+        })(5, 6, 7);
    }
-    expect_exact: "(function(){var arguments=arguments,o=9;console.log(o,arguments)})(5,6,7);"
+    expect_exact: "(function(){var arguments,o=9;console.log(o,arguments)})(5,6,7);"
    expect_stdout: true
 }
--- a/test/compress/join_vars.js
+++ b/test/compress/join_vars.js
@@ -489,6 +489,160 @@ join_object_assignments_regex: {
    expect_stdout: "1"
 }

+chained_assignments: {
+    options = {
+        join_vars: true,
+    }
+    input: {
+        var a, b = a = {};
+        b.p = "PASS";
+        console.log(a.p);
+    }
+    expect: {
+        var a, b = a = {
+            p: "PASS",
+        };
+        console.log(a.p);
+    }
+    expect_stdout: "PASS"
+}
+
+folded_assignments_1: {
+    options = {
+        evaluate: true,
+        join_vars: true,
+    }
+    input: {
+        var a = {};
+        a[a.PASS = 42] = "PASS";
+        console.log(a[42], a.PASS);
+    }
+    expect: {
+        var a = {
+            PASS: 42,
+            42: "PASS",
+        };
+        console.log(a[42], a.PASS);
+    }
+    expect_stdout: "PASS 42"
+}
+
+folded_assignments_2: {
+    options = {
+        evaluate: true,
+        join_vars: true,
+    }
+    input: {
+        "use strict";
+        var a = {};
+        a[42] = "FAIL";
+        a[a.PASS = 42] = "PASS";
+        console.log(a[42], a.PASS);
+    }
+    expect: {
+        "use strict";
+        var a = {
+            42: "FAIL",
+            PASS: 42,
+        };
+        a[42] = "PASS";
+        console.log(a[42], a.PASS);
+    }
+    expect_stdout: "PASS 42"
+}
+
+inlined_assignments: {
+    options = {
+        join_vars: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        (a = {}).p = "PASS";
+        console.log(a.p);
+    }
+    expect: {
+        var a = {
+            p: "PASS",
+        };
+        console.log(a.p);
+    }
+    expect_stdout: "PASS"
+}
+
+inilne_for: {
+    options = {
+        inline: true,
+        join_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = function() {
+            for (; console.log("PASS"););
+        };
+        a();
+    }
+    expect: {
+        for (; console.log("PASS"););
+    }
+    expect_stdout: "PASS"
+}
+
+inilne_var: {
+    options = {
+        inline: true,
+        join_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        A = "PASS";
+        var a = function() {
+            var b = A;
+            for (b in console.log(b));
+        };
+        a();
+    }
+    expect: {
+        A = "PASS";
+        var b = A;
+        for (b in console.log(b));
+    }
+    expect_stdout: "PASS"
+}
+
+typescript_enum: {
+    rename = true
+    options = {
+        assignments: true,
+        collapse_vars: true,
+        evaluate: true,
+        hoist_props: true,
+        inline: true,
+        join_vars: true,
+        passes: 4,
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var Enum;
+        (function (Enum) {
+            Enum[Enum.PASS = 42] = "PASS";
+        })(Enum || (Enum = {}));
+        console.log(Enum[42], Enum.PASS);
+    }
+    expect: {
+        console.log("PASS", 42);
+    }
+    expect_stdout: "PASS 42"
+}
+
 issue_2816: {
    options = {
        join_vars: true,
@@ -1015,7 +1169,7 @@ issue_3856: {
        console.log(function() {
            (function() {
                var a, b;
-                if (a) return !!a;
+                if (a) return a, 1;
                for (a = 0; !console;);
                return 0;
            })();
@@ -1024,7 +1178,7 @@ issue_3856: {
    expect_stdout: "undefined"
 }

-issue_3916: {
+issue_3916_1: {
    options = {
        join_vars: true,
    }
@@ -1044,8 +1198,8 @@ issue_3916: {
        var o = {
            p: "PASS",
            __proto__: 42,
-            q: "FAIL",
        };
+        o.q = "FAIL";
        o.__proto__ = {
            p: "FAIL",
            q: "PASS",
@@ -1056,6 +1210,62 @@ issue_3916: {
    expect_stdout: "object PASS true PASS"
 }

+issue_3916_2: {
+    options = {
+        join_vars: true,
+    }
+    input: {
+        var log = console.log, o = {};
+        o.p = "FAIL 1";
+        o.__proto__ = {
+            get p() {
+                return "FAIL 2";
+            },
+            set p(u) {
+                log("FAIL 3");
+            },
+            set q(v) {
+                log("PASS 1");
+            },
+            get q() {
+                return "PASS 3";
+            },
+        };
+        o.p = "PASS 2";
+        o.q = "FAIL 4";
+        log(o.p);
+        log(o.q);
+    }
+    expect: {
+        var log = console.log, o = {
+            p: "FAIL 1",
+            __proto__: {
+                get p() {
+                    return "FAIL 2";
+                },
+                set p(u) {
+                    log("FAIL 3");
+                },
+                set q(v) {
+                    log("PASS 1");
+                },
+                get q() {
+                    return "PASS 3";
+                },
+            },
+        };
+        o.p = "PASS 2";
+        o.q = "FAIL 4";
+        log(o.p);
+        log(o.q);
+    }
+    expect_stdout: [
+        "PASS 1",
+        "PASS 2",
+        "PASS 3",
+    ]
+}
+
 assign_var: {
    options = {
        join_vars: true,
@@ -1116,10 +1326,7 @@ assign_sequence_var: {
        console.log(a, b, c);
    }
    expect: {
-        var a = 0, b = 1;
-        console.log(a),
-        a++;
-        var b = 2, c = 3;
+        var a = 0, b = 1, c = (console.log(a), a++, b = 2, 3);
        console.log(a, b, c);
    }
    expect_stdout: [
@@ -1127,3 +1334,26 @@ assign_sequence_var: {
        "1 2 3",
    ]
 }
+
+issue_5175: {
+    options = {
+        join_vars: true,
+    }
+    input: {
+        function log(f) {
+            console.log(f(), A.p);
+        }
+        log(function() {
+            return (A = {}).p = "PASS";
+        });
+    }
+    expect: {
+        function log(f) {
+            console.log(f(), A.p);
+        }
+        log(function() {
+            return (A = {}).p = "PASS";
+        });
+    }
+    expect_stdout: "PASS PASS"
+}
--- a/test/compress/keep_fargs.js
+++ b/test/compress/keep_fargs.js
@@ -117,6 +117,7 @@ issue_1858: {
        collapse_vars: true,
        keep_fargs: false,
        pure_getters: true,
+        reduce_vars: true,
        unused: true,
    }
    input: {
@@ -180,10 +181,10 @@ issue_2203_2: {
            a: "FAIL",
            b: function() {
                return function() {
-                    return (String, (Object, function() {
+                    return (Object, function() {
                        return this;
-                    }())).a;
-                }();
+                    }()).a;
+                }(String);
            }
        }.b());
    }
@@ -924,6 +925,28 @@ duplicate_lambda_defun_name_2: {
    expect_stdout: "0"
 }

+function_argument_mangle: {
+    mangle = {
+        keep_fargs: true,
+        toplevel: true,
+    }
+    input: {
+        A = "PASS";
+        var a = A;
+        (function(o) {
+            console.log(a);
+        })("FAIL");
+    }
+    expect: {
+        A = "PASS";
+        var n = A;
+        (function(o) {
+            console.log(n);
+        })("FAIL");
+    }
+    expect_stdout: "PASS"
+}
+
 function_name_mangle: {
    options = {
        keep_fargs: false,
@@ -950,7 +973,7 @@ function_name_mangle_ie8: {
        unused: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -1157,8 +1180,8 @@ replace_all_var_scope: {
        var a = 100, b = 10;
        (function(r, a) {
            switch (~a) {
-            case (b += a):
-            case a++:
+              case (b += a):
+              case a++:
            }
        })(--b, a);
        console.log(a, b);
@@ -1167,8 +1190,8 @@ replace_all_var_scope: {
        var a = 100, b = 10;
        (function(c) {
            switch (~a) {
-            case (b += a):
-            case c++:
+              case (b += a):
+              case c++:
            }
        })((--b, a));
        console.log(a, b);
@@ -1216,6 +1239,7 @@ issues_3267_1: {
        evaluate: true,
        inline: true,
        keep_fargs: false,
+        negate_iife: true,
        reduce_vars: true,
        sequences: true,
        side_effects: true,
@@ -1234,7 +1258,8 @@ issues_3267_1: {
    }
    expect: {
        !function() {
-            if (Object())
+            var i = Object();
+            if (i)
                return console.log("PASS");
            throw "FAIL";
        }();
--- a/test/compress/labels.js
+++ b/test/compress/labels.js
@@ -83,8 +83,9 @@ labels_5: {
        conditionals: true,
        dead_code: true,
        if_return: true,
+        unused: true,
    }
-    // should keep the break-s in the following
+    // should keep `break`s below
    input: {
        while (foo) {
            if (bar) break;
@@ -100,8 +101,8 @@ labels_5: {
            if (bar) break;
            console.log("foo");
        }
-        out: while (foo) {
-            if (bar) break out;
+        while (foo) {
+            if (bar) break;
            console.log("foo");
        }
    }
@@ -189,23 +190,22 @@ labels_10: {
        conditionals: true,
        dead_code: true,
        if_return: true,
+        unused: true,
    }
    input: {
-        out: while (foo) {
-            x();
-            y();
+        out: while (42) {
+            console.log("PASS");
            break out;
-            z();
-            k();
+            console.log("FAIL");
        }
    };
    expect: {
-        out: while (foo) {
-            x();
-            y();
-            break out;
+        while (42) {
+            console.log("PASS");
+            break;
        }
    }
+    expect_stdout: "PASS"
 }

 issue_4466_1: {
--- a/test/compress/let.js
+++ b/test/compress/let.js
@@ -1,4 +1,4 @@
-retain_block: {
+retain_block_1: {
    options = {}
    input: {
        "use strict";
@@ -20,6 +20,127 @@ retain_block: {
    node_version: ">=4"
 }

+retain_block_2: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        {
+            var a;
+            let a;
+        }
+    }
+    expect: {
+        "use strict";
+        {
+            var a;
+            let a;
+        }
+    }
+    expect_stdout: true
+    node_version: ">=4"
+}
+
+retain_block_2_mangle: {
+    rename = true
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        {
+            var a;
+            let a;
+        }
+    }
+    expect: {
+        "use strict";
+        {
+            var t;
+            let t;
+        }
+    }
+}
+
+retain_block_3: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        {
+            let a;
+            var a;
+        }
+    }
+    expect: {
+        "use strict";
+        {
+            let a;
+            var a;
+        }
+    }
+    expect_stdout: true
+    node_version: ">=4"
+}
+
+retain_block_3_mangle: {
+    rename = true
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        {
+            let a;
+            var a;
+        }
+    }
+    expect: {
+        "use strict";
+        {
+            let t;
+            var t;
+        }
+    }
+}
+
+retain_assignment: {
+    options = {
+        dead_code: true,
+        reduce_vars: true,
+    }
+    input: {
+        "use strict";
+        function f() {
+            return a = 0;
+            let a;
+        }
+        try {
+            f();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        "use strict";
+        function f() {
+            return a = 0;
+            let a;
+        }
+        try {
+            f();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 retain_catch: {
    options = {
        dead_code: true,
@@ -149,8 +270,8 @@ merge_vars_3: {
            var b = console;
            console.log(typeof b);
        }
-        var a = 1;
-        console.log(typeof a);
+        var b = 1;
+        console.log(typeof b);
    }
    expect_stdout: [
        "object",
@@ -159,6 +280,38 @@ merge_vars_3: {
    node_version: ">=4"
 }

+merge_vars_4: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        var a = 1;
+        console.log(typeof a);
+        {
+            var b = console;
+            console.log(typeof b);
+            let a = 0;
+        }
+    }
+    expect: {
+        "use strict";
+        var a = 1;
+        console.log(typeof a);
+        {
+            var b = console;
+            console.log(typeof b);
+            let a = 0;
+        }
+    }
+    expect_stdout: [
+        "number",
+        "object",
+    ]
+    node_version: ">=4"
+}
+
 use_before_init_1: {
    options = {
        evaluate: true,
@@ -461,6 +614,41 @@ reduce_vars_3: {
    node_version: ">=4"
 }

+reduce_lambda: {
+    options = {
+        evaluate: true,
+        functions: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        let f = function() {
+            console.log(a, b);
+        };
+        let a = "foo", b = 42;
+        f();
+        b = "bar";
+        f();
+    }
+    expect: {
+        "use strict";
+        function f() {
+            console.log("foo", b);
+        }
+        let b = 42;
+        f();
+        b = "bar";
+        f();
+    }
+    expect_stdout: [
+        "foo 42",
+        "foo bar",
+    ]
+    node_version: ">=4"
+}
+
 hoist_props: {
    options = {
        hoist_props: true,
@@ -536,6 +724,38 @@ loop_block_2: {
    node_version: ">=4"
 }

+do_break: {
+    options = {
+        loops: true,
+    }
+    input: {
+        "use strict";
+        try {
+            do {
+                if (a)
+                    break;
+                let a;
+            } while (!console);
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        "use strict";
+        try {
+            do {
+                if (a)
+                    break;
+                let a;
+            } while (!console);
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 do_continue: {
    options = {
        loops: true,
@@ -596,6 +816,82 @@ dead_block_after_return: {
    node_version: ">=4"
 }

+if_return_1: {
+    options = {
+        if_return: true,
+    }
+    input: {
+        "use strict";
+        function f(a) {
+            function g() {
+                return b = "PASS";
+            }
+            if (a)
+                return g();
+            let b;
+            return g();
+        };
+        console.log(f());
+    }
+    expect: {
+        "use strict";
+        function f(a) {
+            function g() {
+                return b = "PASS";
+            }
+            if (a)
+                return g();
+            let b;
+            return g();
+        };
+        console.log(f());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+if_return_2: {
+    options = {
+        if_return: true,
+    }
+    input: {
+        "use strict";
+        function f(a) {
+            function g() {
+                return b = "FAIL";
+            }
+            if (a)
+                return g();
+            let b;
+            return g();
+        };
+        try {
+            console.log(f(42));
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        "use strict";
+        function f(a) {
+            function g() {
+                return b = "FAIL";
+            }
+            if (a)
+                return g();
+            let b;
+            return g();
+        };
+        try {
+            console.log(f(42));
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 do_if_continue_1: {
    options = {
        if_return: true,
@@ -790,12 +1086,10 @@ issue_4202: {
        "use strict";
        {
            let o = {};
-            (function() {
-                function f() {
-                    o.p = 42;
-                }
-                f(f);
-            })();
+            function f() {
+                o.p = 42;
+            }
+            f(f);
            console.log(o.p++);
        }
    }
@@ -897,6 +1191,7 @@ issue_4210: {
 issue_4212_1: {
    options = {
        dead_code: true,
+        reduce_vars: true,
    }
    input: {
        "use strict";
@@ -987,7 +1282,7 @@ issue_4225: {

 issue_4229: {
    options = {
-        ie8: true,
+        ie: true,
        side_effects: true,
    }
    input: {
@@ -1018,7 +1313,7 @@ issue_4229: {

 issue_4231: {
    options = {
-        ie8: true,
+        ie: true,
        side_effects: true,
    }
    input: {
@@ -1376,7 +1671,7 @@ issue_4438: {
                ;
            else {
                let a = console.log;
-                a("PASS");
+                void a("PASS");
            }
        }
        f();
@@ -1387,7 +1682,7 @@ issue_4438: {

 issue_4531_1: {
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -1413,11 +1708,11 @@ issue_4531_1: {
 issue_4531_2: {
    options = {
        evaluate: true,
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -1506,3 +1801,175 @@ issue_4691: {
    expect_stdout: "PASS"
    node_version: ">=4"
 }
+
+issue_4848: {
+    options = {
+        if_return: true,
+    }
+    input: {
+        "use strict";
+        function f(a) {
+            a(function() {
+                console.log(b);
+            });
+            if (!console)
+                return;
+            let b = "PASS";
+        }
+        var g;
+        f(function(h) {
+            g = h;
+        });
+        g();
+    }
+    expect: {
+        "use strict";
+        function f(a) {
+            a(function() {
+                console.log(b);
+            });
+            if (!console)
+                return;
+            let b = "PASS";
+        }
+        var g;
+        f(function(h) {
+            g = h;
+        });
+        g();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_4985: {
+    options = {
+        hoist_props: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        let a = { p: 42 };
+        console.log(function() {
+            a;
+        }());
+    }
+    expect: {
+        "use strict";
+        let a = { p: 42 };
+        console.log(function() {
+            a;
+        }());
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}
+
+issue_5240: {
+    options = {
+        inline: true,
+    }
+    input: {
+        "use strict";
+        function f() {
+            if (console) {
+                let g = function() {
+                    e;
+                }, e;
+                (function() {
+                    if (console) {
+                        console.log(e);
+                        var e = "FAIL";
+                    }
+                })(console.log(e));
+            }
+        }
+        f();
+    }
+    expect: {
+        "use strict";
+        function f() {
+            if (console) {
+                let g = function() {
+                    e;
+                }, e;
+                (function() {
+                    if (console) {
+                        console.log(e);
+                        var e = "FAIL";
+                    }
+                })(console.log(e));
+            }
+        }
+        f();
+    }
+    expect_stdout: [
+        "undefined",
+        "undefined",
+    ]
+    node_version: ">=4"
+}
+
+issue_5254: {
+    options = {
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        do {
+            (function() {
+                let a = console.log;
+                a && a("foo");
+            })();
+        } while (console.log("bar"));
+    }
+    expect: {
+        "use strict";
+        do {
+            let a = console.log;
+            a && a("foo");
+        } while (console.log("bar"));
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+    node_version: ">=4"
+}
+
+issue_5260: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        "use strict";
+        var a = "foo", o;
+        while (console.log("bar"));
+        o = {
+            baz: function(b) {
+                console.log(a, b);
+            },
+        };
+        for (let a in o)
+            o[a](a);
+    }
+    expect: {
+        "use strict";
+        var a = "foo", o;
+        while (console.log("bar"));
+        o = {
+            baz: function(b) {
+                console.log(a, b);
+            },
+        };
+        for (let a in o)
+            o[a](a);
+    }
+    expect_stdout: [
+        "bar",
+        "foo baz",
+    ]
+    node_version: ">=4"
+}
--- a/test/compress/loops.js
+++ b/test/compress/loops.js
@@ -193,9 +193,9 @@ evaluate: {
        } while (false);
    }
    expect: {
-        for(;;)
+        for (;;)
            a();
-        for(;;)
+        for (;;)
            c();
        d();
    }
@@ -265,7 +265,7 @@ issue_1532_2: {
 issue_186: {
    beautify = {
        beautify: false,
-        ie8: false,
+        ie: false,
    }
    input: {
        var x = 3;
@@ -284,7 +284,7 @@ issue_186: {
 issue_186_ie8: {
    beautify = {
        beautify: false,
-        ie8: true,
+        ie: true,
    }
    input: {
        var x = 3;
@@ -303,7 +303,7 @@ issue_186_ie8: {
 issue_186_beautify: {
    beautify = {
        beautify: true,
-        ie8: false,
+        ie: false,
    }
    input: {
        var x = 3;
@@ -330,7 +330,7 @@ issue_186_beautify: {
 issue_186_beautify_ie8: {
    beautify = {
        beautify: true,
-        ie8: true,
+        ie: true,
    }
    input: {
        var x = 3;
@@ -360,7 +360,7 @@ issue_186_braces: {
    beautify = {
        beautify: false,
        braces: true,
-        ie8: false,
+        ie: false,
    }
    input: {
        var x = 3;
@@ -380,7 +380,7 @@ issue_186_braces_ie8: {
    beautify = {
        beautify: false,
        braces: true,
-        ie8: true,
+        ie: true,
    }
    input: {
        var x = 3;
@@ -400,7 +400,7 @@ issue_186_beautify_braces: {
    beautify = {
        beautify: true,
        braces: true,
-        ie8: false,
+        ie: false,
    }
    input: {
        var x = 3;
@@ -432,7 +432,7 @@ issue_186_beautify_braces_ie8: {
    beautify = {
        beautify: true,
        braces: true,
-        ie8: true,
+        ie: true,
    }
    input: {
        var x = 3;
@@ -829,6 +829,18 @@ empty_for_in_prop_init: {
 }

 for_of: {
+    input: {
+        var a = [ "PASS", 42 ];
+        a.p = "FAIL";
+        for (a of (null, a))
+            console.log(a);
+    }
+    expect_exact: 'var a=["PASS",42];a.p="FAIL";for(a of(null,a))console.log(a);'
+    expect_stdout: true
+    node_version: ">=0.12"
+}
+
+for_async_of: {
    input: {
        var async = [ "PASS", 42 ];
        async.p = "FAIL";
@@ -837,7 +849,21 @@ for_of: {
    }
    expect_exact: 'var async=["PASS",42];async.p="FAIL";for(async of(null,async))console.log(async);'
    expect_stdout: true
-    node_version: ">=0.12"
+    node_version: ">=0.12 <16"
+}
+
+for_of_regexp: {
+    input: {
+        for (var a of /foo/);
+    }
+    expect_exact: "for(var a of/foo/);"
+}
+
+for_await_of_regexp: {
+    input: {
+        for await (var a of /foo/);
+    }
+    expect_exact: "for await(var a of/foo/);"
 }

 issue_3631_1: {
--- a/test/compress/merge_vars.js
+++ b/test/compress/merge_vars.js
@@ -19,11 +19,11 @@ merge: {
    expect: {
        var a = "foo";
        console.log(a);
-        function f(c) {
-            var c;
-            console.log(c);
-            c = "bar";
-            console.log(c);
+        function f(b) {
+            var b;
+            console.log(b);
+            b = "bar";
+            console.log(b);
        }
        f("baz");
        var d = "moo";
@@ -56,17 +56,17 @@ merge_toplevel: {
        console.log(d);
    }
    expect: {
-        var d = "foo";
-        console.log(d);
-        function f(c) {
-            var c;
-            console.log(c);
-            c = "bar";
-            console.log(c);
+        var a = "foo";
+        console.log(a);
+        function f(b) {
+            var b;
+            console.log(b);
+            b = "bar";
+            console.log(b);
        }
        f("baz");
-        var d = "moo";
-        console.log(d);
+        var a = "moo";
+        console.log(a);
    }
    expect_stdout: [
        "foo",
@@ -94,16 +94,16 @@ segment: {
        console.log(d);
    }
    expect: {
-        var d = "foo";
-        console.log(d);
-        for (var c, i = 0; i < 1; i++) {
-            var c = "bar";
-            console.log(c);
-            c = "baz";
-            console.log(c);
+        var a = "foo";
+        console.log(a);
+        for (var b, i = 0; i < 1; i++) {
+            var b = "bar";
+            console.log(b);
+            b = "baz";
+            console.log(b);
        }
-        var d = "moo";
-        console.log(d);
+        var a = "moo";
+        console.log(a);
    }
    expect_stdout: [
        "foo",
@@ -298,6 +298,89 @@ read_before_assign_2: {
    expect_stdout: "PASS"
 }

+collapse_vars_1: {
+    options = {
+        collapse_vars: true,
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = a && a.p;
+        var b = "PASS";
+        var b = b && console.log(b);
+    }
+    expect: {
+        var a = a && a.p;
+        var a;
+        var a = (a = "PASS") && console.log(a);
+    }
+    expect_stdout: "PASS"
+}
+
+collapse_vars_2: {
+    options = {
+        collapse_vars: true,
+        merge_vars: true,
+    }
+    input: {
+        "use strict";
+        var log = console.log;
+        (function g(a) {
+            var b = a;
+            var c = Math.random();
+            var c = b;
+            log(c);
+            return c;
+        })("PASS");
+    }
+    expect: {
+        "use strict";
+        var log = console.log;
+        (function g(a) {
+            var a = a;
+            var c = Math.random();
+            var c;
+            log(c = a);
+            return c;
+        })("PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+not_redefined: {
+    options = {
+        inline: true,
+        join_vars: true,
+        merge_vars: true,
+        reduce_vars: true,
+        unused: true,
+        varify: true,
+    }
+    input: {
+        var log = console.log;
+        (function() {
+            return f("PASS");
+            function f(a) {
+                const b = a;
+                const c = log(b);
+                const d = log;
+                c && log(d);
+            }
+        })();
+    }
+    expect: {
+        var log = console.log;
+        (function() {
+            return a = "PASS",
+                a = log(a),
+                d = log,
+                void (a && log(d));
+            var a, d;
+        })();
+    }
+    expect_stdout: "PASS"
+}
+
 issue_4103: {
    options = {
        merge_vars: true,
@@ -325,7 +408,7 @@ issue_4103: {
    ]
 }

-issue_4107: {
+issue_4107_1: {
    options = {
        keep_fargs: false,
        merge_vars: true,
@@ -342,6 +425,38 @@ issue_4107: {
        })();
        console.log(typeof a);
    }
+    expect: {
+        (function() {
+            (function(c) {
+                c = console || c;
+                console.log(typeof c);
+            })();
+        })();
+        console.log(typeof a);
+    }
+    expect_stdout: [
+        "object",
+        "undefined",
+    ]
+}
+
+issue_4107_2: {
+    options = {
+        keep_fargs: false,
+        merge_vars: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function() {
+            function f(b, b, a) {
+                var d = 1 && c, c = console || a;
+                console.log(typeof c);
+            }
+            f();
+        })();
+        console.log(typeof a);
+    }
    expect: {
        (function() {
            (function(a) {
@@ -359,7 +474,7 @@ issue_4107: {

 issue_4109: {
    options = {
-        ie8: true,
+        ie: true,
        merge_vars: true,
        toplevel: true,
    }
@@ -476,9 +591,9 @@ issue_4112: {
            try {
                throw 42;
            } catch (e) {
-                var a = e;
-                for (e in a);
-                a = function() {};
+                var o = e;
+                for (e in o);
+                function a() {}
                console.log(typeof a);
                return a;
            }
@@ -538,12 +653,12 @@ cross_branch_1_1: {
    expect: {
        var a;
        function f() {
-            var y, y;
+            var x, x;
            if (a)
-                y = "foo";
-            console.log(y);
-            y = "bar";
-            console.log(y);
+                x = "foo";
+            console.log(x);
+            x = "bar";
+            console.log(x);
        }
        a = 0;
        f();
@@ -581,13 +696,13 @@ cross_branch_1_2: {
    expect: {
        var a;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
-                y = "foo";
-                console.log(y);
+                x = "foo";
+                console.log(x);
            }
-            y = "bar";
-            console.log(y);
+            x = "bar";
+            console.log(x);
        }
        a = 0;
        f();
@@ -624,13 +739,13 @@ cross_branch_1_3: {
    expect: {
        var a;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
-                y = "foo";
-                console.log(y);
-                y = "bar";
+                x = "foo";
+                console.log(x);
+                x = "bar";
            }
-            console.log(y);
+            console.log(x);
        }
        a = 0;
        f();
@@ -666,12 +781,12 @@ cross_branch_1_4: {
    expect: {
        var a;
        function f() {
-            var y, y;
-            y = "foo";
+            var x, x;
+            x = "foo";
            if (a)
-                console.log(y);
-            y = "bar";
-            console.log(y);
+                console.log(x);
+            x = "bar";
+            console.log(x);
        }
        a = 0;
        f();
@@ -751,12 +866,12 @@ cross_branch_1_6: {
    expect: {
        var a;
        function f() {
-            var y, y;
-            y = "foo";
+            var x, x;
+            x = "foo";
            if (a) {
-                console.log(y);
-                y = "bar";
-                console.log(y);
+                console.log(x);
+                x = "bar";
+                console.log(x);
            }
        }
        a = 0;
@@ -835,12 +950,12 @@ cross_branch_1_8: {
    expect: {
        var a;
        function f() {
-            var y, y;
-            y = "foo";
-            console.log(y);
+            var x, x;
+            x = "foo";
+            console.log(x);
            if (a) {
-                y = "bar";
-                console.log(y);
+                x = "bar";
+                console.log(x);
            }
        }
        a = 0;
@@ -877,12 +992,12 @@ cross_branch_1_9: {
    expect: {
        var a;
        function f() {
-            var y, y;
-            y = "foo";
-            console.log(y);
-            y = "bar";
+            var x, x;
+            x = "foo";
+            console.log(x);
+            x = "bar";
            if (a)
-                console.log(y);
+                console.log(x);
        }
        a = 0;
        f();
@@ -924,14 +1039,14 @@ cross_branch_2a_1: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
                if (b)
-                    y = "foo";
-                console.log(y);
+                    x = "foo";
+                console.log(x);
            }
-            y = "bar";
-            console.log(y);
+            x = "bar";
+            console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -980,14 +1095,14 @@ cross_branch_2a_2: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
-                y = "foo";
+                x = "foo";
                if (b)
-                    console.log(y);
+                    console.log(x);
            }
-            y = "bar";
-            console.log(y);
+            x = "bar";
+            console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -1035,14 +1150,14 @@ cross_branch_2a_3: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
                if (b)
-                    y = "foo";
-                console.log(y);
-                y = "bar";
+                    x = "foo";
+                console.log(x);
+                x = "bar";
            }
-            console.log(y);
+            console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -1092,15 +1207,15 @@ cross_branch_2a_4: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
                if (b) {
-                    y = "foo";
-                    console.log(y);
+                    x = "foo";
+                    console.log(x);
                }
-                y = "bar";
+                x = "bar";
            }
-            console.log(y);
+            console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -1148,14 +1263,14 @@ cross_branch_2a_5: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
-                y = "foo";
+                x = "foo";
                if (b)
-                    console.log(y);
-                y = "bar";
+                    console.log(x);
+                x = "bar";
            }
-            console.log(y);
+            console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -1427,13 +1542,13 @@ cross_branch_2a_10: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
-            y = "foo";
+            var x, x;
+            x = "foo";
            if (a) {
                if (b)
-                    console.log(y);
-                y = "bar";
-                console.log(y);
+                    console.log(x);
+                x = "bar";
+                console.log(x);
            }
        }
        a = 0, b = 0;
@@ -1590,13 +1705,13 @@ cross_branch_2a_13: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
-            y = "foo";
+            var x, x;
+            x = "foo";
            if (a) {
-                console.log(y);
+                console.log(x);
                if (b) {
-                    y = "bar";
-                    console.log(y);
+                    x = "bar";
+                    console.log(x);
                }
            }
        }
@@ -1644,13 +1759,13 @@ cross_branch_2a_14: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
-            y = "foo";
+            var x, x;
+            x = "foo";
            if (a) {
-                console.log(y);
-                y = "bar";
+                console.log(x);
+                x = "bar";
                if (b)
-                    console.log(y);
+                    console.log(x);
            }
        }
        a = 0, b = 0;
@@ -1753,13 +1868,13 @@ cross_branch_2a_16: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
-            y = "foo";
-            console.log(y);
+            var x, x;
+            x = "foo";
+            console.log(x);
            if (a) {
-                y = "bar";
+                x = "bar";
                if (b)
-                    console.log(y);
+                    console.log(x);
            }
        }
        a = 0, b = 0;
@@ -1807,13 +1922,13 @@ cross_branch_2b_1: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a)
-                y = "foo";
+                x = "foo";
            if (b)
-                console.log(y);
-            y = "bar";
-            console.log(y);
+                console.log(x);
+            x = "bar";
+            console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -1918,13 +2033,13 @@ cross_branch_2b_3: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a)
-                y = "foo";
+                x = "foo";
            if (b) {
-                console.log(y);
-                y = "bar";
-                console.log(y);
+                console.log(x);
+                x = "bar";
+                console.log(x);
            }
        }
        a = 0, b = 0;
@@ -2028,13 +2143,13 @@ cross_branch_2b_5: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a)
-                y = "foo";
-            console.log(y);
+                x = "foo";
+            console.log(x);
            if (b) {
-                y = "bar";
-                console.log(y);
+                x = "bar";
+                console.log(x);
            }
        }
        a = 0, b = 0;
@@ -2141,14 +2256,14 @@ cross_branch_2b_7: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
-                y = "foo";
-                console.log(y);
+                x = "foo";
+                console.log(x);
            }
            if (b) {
-                y = "bar";
-                console.log(y);
+                x = "bar";
+                console.log(x);
            }
        }
        a = 0, b = 0;
@@ -2195,13 +2310,13 @@ cross_branch_2b_8: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a)
-                y = "foo";
-            console.log(y);
-            y = "bar";
+                x = "foo";
+            console.log(x);
+            x = "bar";
            if (b)
-                console.log(y);
+                console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -2250,14 +2365,14 @@ cross_branch_2b_9: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
-                y = "foo";
-                console.log(y);
+                x = "foo";
+                console.log(x);
            }
-            y = "bar";
+            x = "bar";
            if (b)
-                console.log(y);
+                console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -2304,14 +2419,14 @@ cross_branch_2b_10: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
+            var x, x;
            if (a) {
-                y = "foo";
-                console.log(y);
-                y = "bar";
+                x = "foo";
+                console.log(x);
+                x = "bar";
            }
            if (b)
-                console.log(y);
+                console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -2412,13 +2527,13 @@ cross_branch_2b_12: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
-            y = "foo";
+            var x, x;
+            x = "foo";
            if (a)
-                console.log(y);
+                console.log(x);
            if (b) {
-                y = "bar";
-                console.log(y);
+                x = "bar";
+                console.log(x);
            }
        }
        a = 0, b = 0;
@@ -2465,13 +2580,13 @@ cross_branch_2b_13: {
    expect: {
        var a, b;
        function f() {
-            var y, y;
-            y = "foo";
+            var x, x;
+            x = "foo";
            if (a)
-                console.log(y);
-            y = "bar";
+                console.log(x);
+            x = "bar";
            if (b)
-                console.log(y);
+                console.log(x);
        }
        a = 0, b = 0;
        f();
@@ -2620,11 +2735,11 @@ issue_4126_1: {
            try {
                console.log("PASS");
            } catch (e) {
-                var c = a;
+                var b = a;
            } finally {
-                var c = c;
+                var a = b;
            }
-            console.log(c);
+            console.log(a);
        }
        f("FAIL");
    }
@@ -2735,8 +2850,7 @@ issue_4135: {
        0;
        a++;
        if (!a)
-            c = (a++, c = 0, void (c && c.p));
-        var c;
+            var c = void a++;
        console.log(a, -1, c);
    }
    expect_stdout: "1 -1 undefined"
@@ -2817,11 +2931,11 @@ conditional_write: {
        console.log(b);
    }
    expect: {
-        var b = "FAIL", b;
+        var a = "FAIL", a;
        if (console)
-            b = "PASS";
-        b = [b, 42].join();
-        console.log(b);
+            a = "PASS";
+        a = [a, 42].join();
+        console.log(a);
    }
    expect_stdout: "PASS,42"
 }
@@ -2995,13 +3109,13 @@ issue_4168_use_strict: {
    expect: {
        "use strict";
        var o = {
-            f: function(d, e, f) {
-                var d = d.d;
-                var e = e.e;
-                var f = f.f;
+            f: function(a, b, c) {
+                var a = a.d;
+                var b = b.e;
+                var c = c.f;
                this.g(arguments);
-                if (d)
-                    console.log(e, f);
+                if (a)
+                    console.log(b, c);
            },
            g: function(args) {
                console.log(args[0], args[1], args[2]);
@@ -3075,7 +3189,7 @@ issue_4237_2: {
        console.log(function(a) {
            do {
                switch (0) {
-                  case 0:
+                  default:
                    var b = a++;
                    if (b)
                        return "FAIL";
@@ -3229,10 +3343,10 @@ issue_4653: {
        f(a++ + (b = b), b |= console.log(a));
    }
    expect: {
-        var b = 1;
+        var b, a = 1;
        (function(c, d) {
            c || console.log(d);
-        })(+b + (b = void 0), b |= console.log(2));
+        })(+a + (b = b), b |= console.log(2));
    }
    expect_stdout: [
        "2",
@@ -3301,3 +3415,137 @@ issue_4761: {
    }
    expect_stdout: "undefined"
 }
+
+issue_4956_1: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a, b;
+        function f(c) {
+            switch (c) {
+              case 0:
+                a = { p: 42 };
+
+              case 1:
+                b = a.p;
+                console.log(b);
+            }
+        }
+        f(0);
+        f(1);
+    }
+    expect: {
+        var a, b;
+        function f(c) {
+            switch (c) {
+              case 0:
+                a = { p: 42 };
+
+              case 1:
+                b = a.p;
+                console.log(b);
+            }
+        }
+        f(0);
+        f(1);
+    }
+    expect_stdout: [
+        "42",
+        "42",
+    ]
+}
+
+issue_4956_2: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a, b;
+        function f(c) {
+            if (0 == c) {
+                console;
+                a = { p: 42 };
+            }
+            b = a.p;
+            if (1 == c)
+                console.log(b);
+        }
+        f(0);
+        f(1);
+    }
+    expect: {
+        var a, b;
+        function f(c) {
+            if (0 == c) {
+                console;
+                a = { p: 42 };
+            }
+            b = a.p;
+            if (1 == c)
+                console.log(b);
+        }
+        f(0);
+        f(1);
+    }
+    expect_stdout: "42"
+}
+
+issue_5182: {
+    options = {
+        arrows: true,
+        collapse_vars: true,
+        evaluate: true,
+        hoist_props: true,
+        inline: true,
+        merge_vars: true,
+        passes: 4,
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        try {
+            var con = console;
+        } catch (x) {}
+        global.log = con.log;
+        var jump = function(x) {
+            console.log("JUMP:", x * 10);
+            return x + x;
+        };
+        var jump2 = jump;
+        var run = function(x) {
+            console.log("RUN:", x * -10);
+            return x * x;
+        };
+        var run2 = run;
+        var bar = (x, y) => {
+            console.log("BAR:", x + y);
+            return x - y;
+        };
+        var bar2 = bar;
+        var obj = {
+            foo: bar2,
+            go: run2,
+            not_used: jump2,
+        };
+        console.log(obj.foo(1, 2), global.log("PASS"));
+    }
+    expect: {
+        try {
+            var con = console;
+        } catch (x) {}
+        global.log = con.log,
+        console.log((console.log("BAR:", 3), -1), global.log("PASS"));
+    }
+    expect_stdout: [
+        "BAR: 3",
+        "PASS",
+        "-1 undefined",
+    ]
+    node_version: ">=4"
+}
--- a/test/compress/negate-iife.js
+++ b/test/compress/negate-iife.js
@@ -389,6 +389,7 @@ issue_1288_side_effects: {
    options = {
        conditionals: true,
        negate_iife: true,
+        sequences: true,
        side_effects: true,
    }
    input: {
@@ -409,10 +410,10 @@ issue_1288_side_effects: {
            })(0);
    }
    expect: {
-        w;
+        w,
        x || function() {
            x = {};
-        }();
+        }(),
        y;
    }
 }
--- a/test/compress/nullish.js
+++ b/test/compress/nullish.js
@@ -110,10 +110,186 @@ conditional_assignment_4: {
    node_version: ">=14"
 }

+de_morgan_1: {
+    options = {
+        booleans: true,
+    }
+    input: {
+        function f(a) {
+            return a ?? a;
+        }
+        console.log(f(null), f(42));
+    }
+    expect: {
+        function f(a) {
+            return a;
+        }
+        console.log(f(null), f(42));
+    }
+    expect_stdout: "null 42"
+    node_version: ">=14"
+}
+
+de_morgan_2a: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        evaluate: true,
+    }
+    input: {
+        function f(a, b) {
+            return a || (a ?? b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a || (a ?? b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "undefined {}",
+        "42 42",
+    ]
+    node_version: ">=14"
+}
+
+de_morgan_2b: {
+    options = {
+        booleans: true,
+        evaluate: true,
+    }
+    input: {
+        function f(a, b) {
+            return a && (a ?? b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a;
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "null null",
+        "42 42",
+    ]
+    node_version: ">=14"
+}
+
+de_morgan_2c: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        function f(a, b) {
+            return a ?? (a || b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a ?? b;
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "undefined {}",
+        "42 42",
+    ]
+    node_version: ">=14"
+}
+
+de_morgan_2d: {
+    options = {
+        booleans: true,
+        evaluate: true,
+    }
+    input: {
+        function f(a, b) {
+            return a ?? (a && b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a;
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "null null",
+        "42 42",
+    ]
+    node_version: ">=14"
+}
+
+de_morgan_2e: {
+    options = {
+        booleans: true,
+        conditionals: true,
+    }
+    input: {
+        function f(a, b) {
+            return a ?? (a ?? b);
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect: {
+        function f(a, b) {
+            return a ?? b;
+        }
+        console.log(f(null), f(null, {}));
+        console.log(f(42), f(42, {}));
+    }
+    expect_stdout: [
+        "undefined {}",
+        "42 42",
+    ]
+    node_version: ">=14"
+}
+
+inline_binary_nullish: {
+    options = {
+        inline: true,
+    }
+    input: {
+        (function() {
+            while (console.log("foo"));
+        })() ?? (function() {
+            while (console.log("bar"));
+        })();
+    }
+    expect: {
+        if (null == function() {
+            while (console.log("foo"));
+        }())
+            while (console.log("bar"));
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+    node_version: ">=14"
+}
+
 issue_4679: {
    options = {
        comparisons: true,
-        ie8: true,
+        ie: true,
    }
    input: {
        var a;
@@ -128,3 +304,42 @@ issue_4679: {
    expect_stdout: "PASS"
    node_version: ">=14"
 }
+
+issue_5266: {
+    options = {
+        inline: true,
+    }
+    input: {
+        [
+            42,
+            null,
+            false,
+            void 0,
+            "FAIL",
+        ].forEach(function (a) {
+            a ?? function() {
+                while (console.log(a));
+            }();
+        });
+    }
+    expect: {
+        [
+            42,
+            null,
+            false,
+            void 0,
+            "FAIL",
+        ].forEach(function (a) {
+            if (null == a) {
+                while (console.log(a));
+                return;
+            } else
+                return;
+        });
+    }
+    expect_stdout: [
+        "null",
+        "undefined",
+    ]
+    node_version: ">=14"
+}
--- a/test/compress/numbers.js
+++ b/test/compress/numbers.js
@@ -104,6 +104,40 @@ parentheses_for_prototype_functions_galio: {
    expect_stdout: true
 }

+octal: {
+    beautify = {
+        beautify: true,
+    }
+    input: {
+        (function() {
+            console.log(052);
+            console.log(-052);
+
+            console.log(018);
+            console.log(-018);
+
+            console.log(052.toFixed(0));
+            console.log(-052.toFixed(0));
+
+            console.log(018..toFixed(0));
+            console.log(-018..toFixed(0));
+        })();
+    }
+    expect_exact: [
+        "(function() {",
+        "    console.log(42);",
+        "    console.log(-42);",
+        "    console.log(18);",
+        "    console.log(-18);",
+        "    console.log(42..toFixed(0));",
+        "    console.log(-42..toFixed(0));",
+        "    console.log(18..toFixed(0));",
+        "    console.log(-18..toFixed(0));",
+        "})();",
+    ]
+    expect_stdout: true
+}
+
 comparisons: {
    options = {
        comparisons: true,
--- a/test/compress/objects.js
+++ b/test/compress/objects.js
@@ -521,3 +521,25 @@ issue_4415: {
    expect_stdout: "PASS"
    node_version: ">=4"
 }
+
+issue_5213: {
+    options = {
+        objects: true,
+    }
+    input: {
+        var a = "FAIL";
+        console.log({
+            p: a = "PASS",
+            0: a,
+            p: null,
+        }[0]);
+    }
+    expect: {
+        var a = "FAIL";
+        console.log({
+            p: (a = "PASS", null),
+            0: a,
+        }[0]);
+    }
+    expect_stdout: "PASS"
+}
--- a/test/compress/optional-chains.js
+++ b/test/compress/optional-chains.js
@@ -0,0 +1,619 @@
+call: {
+    input: {
+        console.log?.(undefined?.(console.log("FAIL")));
+    }
+    expect_exact: 'console.log?.((void 0)?.(console.log("FAIL")));'
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+dot: {
+    input: {
+        console?.log((void 0)?.p);
+    }
+    expect_exact: "console?.log((void 0)?.p);"
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+dot_in: {
+    input: {
+        var o = { in: 42 };
+        console.log(o.in, o?.in);
+    }
+    expect_exact: "var o={in:42};console.log(o.in,o?.in);"
+    expect_stdout: "42 42"
+    node_version: ">=14"
+}
+
+sub: {
+    input: {
+        console?.["log"](null?.[console.log("FAIL")]);
+    }
+    expect_exact: 'console?.["log"](null?.[console.log("FAIL")]);'
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+ternary_decimal: {
+    input: {
+        null ? .42 : console.log("PASS");
+    }
+    expect_exact: 'null?.42:console.log("PASS");'
+    expect_stdout: "PASS"
+}
+
+assign_parentheses_call: {
+    input: {
+        var o = {};
+        ((() => o)?.()).p = "PASS";
+        console.log(o.p);
+    }
+    expect_exact: 'var o={};((()=>o)?.()).p="PASS";console.log(o.p);'
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+assign_parentheses_dot: {
+    input: {
+        (console?.log).name.p = console.log("PASS");
+    }
+    expect_exact: '(console?.log).name.p=console.log("PASS");'
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+assign_no_parentheses: {
+    input: {
+        console[console.log?.("PASS")] = 42;
+    }
+    expect_exact: 'console[console.log?.("PASS")]=42;'
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+call_parentheses: {
+    input: {
+        (function(o) {
+            console.log(o.f("FAIL"), (o.f)("FAIL"), (0, o.f)(42));
+            console.log(o?.f("FAIL"), (o?.f)("FAIL"), (0, o?.f)(42));
+        })({
+            a: "PASS",
+            f(b) {
+                return this.a || b;
+            },
+        });
+    }
+    expect_exact: '(function(o){console.log(o.f("FAIL"),o.f("FAIL"),(0,o.f)(42));console.log(o?.f("FAIL"),(o?.f)("FAIL"),(0,o?.f)(42))})({a:"PASS",f(b){return this.a||b}});'
+    expect_stdout: [
+        "PASS PASS 42",
+        "PASS PASS 42",
+    ]
+    node_version: ">=14"
+}
+
+unary_parentheses: {
+    input: {
+        var o = { p: 41 };
+        (function() {
+            return o;
+        }?.()).p++;
+        console.log(o.p);
+    }
+    expect_exact: "var o={p:41};(function(){return o}?.()).p++;console.log(o.p);"
+    expect_stdout: "42"
+    node_version: ">=14"
+}
+
+collapse_vars_1: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a;
+        A = 42;
+        a?.[42];
+        console.log(typeof A);
+    }
+    expect: {
+        var a;
+        A = 42;
+        a?.[42];
+        console.log(typeof A);
+    }
+    expect_stdout: "number"
+    node_version: ">=14"
+}
+
+collapse_vars_2: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a;
+        A = 42;
+        a?.(42);
+        console.log(typeof A);
+    }
+    expect: {
+        var a;
+        A = 42;
+        a?.(42);
+        console.log(typeof A);
+    }
+    expect_stdout: "number"
+    node_version: ">=14"
+}
+
+properties: {
+    options = {
+        evaluate: true,
+        properties: true,
+    }
+    input: {
+        var a;
+        console.log(a?.["FAIL"]);
+    }
+    expect: {
+        var a;
+        console.log(a?.FAIL);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+reduce_vars_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 1;
+        null?.[a = 0];
+        console.log(a ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = 1;
+        null?.[a = 0];
+        console.log(a ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+reduce_vars_2: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 1;
+        null?.(a = 0);
+        console.log(a ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = 1;
+        null?.(a = 0);
+        console.log(a ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+side_effects: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        var a;
+        a?.[a = "FAIL"];
+        console.log(a);
+    }
+    expect: {
+        var a;
+        a?.[a = "FAIL"];
+        console.log(a);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+trim_1: {
+    options = {
+        evaluate: true,
+        optional_chains: true,
+        reduce_vars: true,
+        unsafe: true,
+    }
+    input: {
+        (function(a, b) {
+            console?.log?.(a?.p, b?.[console.log("FAIL")]);
+        })?.({ p: "PASS" });
+    }
+    expect: {
+        (function(a, b) {
+            console?.log?.(a.p, void 0);
+        })({ p: "PASS" });
+    }
+    expect_stdout: "PASS undefined"
+    node_version: ">=14"
+}
+
+trim_2: {
+    options = {
+        evaluate: true,
+        optional_chains: true,
+        side_effects: true,
+    }
+    input: {
+        (void console.log("PASS"))?.[console.log("FAIL")];
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+trim_dot_call_1: {
+    options = {
+        evaluate: true,
+        optional_chains: true,
+    }
+    input: {
+        console.log(null?.f());
+    }
+    expect: {
+        console.log(void 0);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+trim_dot_call_2: {
+    options = {
+        evaluate: true,
+        optional_chains: true,
+        unsafe: true,
+    }
+    input: {
+        try {
+            (null?.p)();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            (void 0)();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+trim_dot_call_3: {
+    options = {
+        evaluate: true,
+        optional_chains: true,
+        unsafe: true,
+    }
+    input: {
+        try {
+            ({ p: null })?.p();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            null();
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+trim_dot_sub: {
+    options = {
+        evaluate: true,
+        optional_chains: true,
+    }
+    input: {
+        console.log(null?.p[42]);
+    }
+    expect: {
+        console.log(void 0);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+trim_sub_call_call: {
+    options = {
+        evaluate: true,
+        optional_chains: true,
+    }
+    input: {
+        console.log(null?.[42]()());
+    }
+    expect: {
+        console.log(void 0);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+issue_4906: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        do {
+            var a = a?.[42];
+        } while (console.log("PASS"));
+    }
+    expect: {
+        do {
+            var a = a?.[42];
+        } while (console.log("PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+issue_4928: {
+    options = {
+        ie: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = a?.[function f() {
+            f(a);
+        }];
+        console.log(typeof f);
+    }
+    expect: {
+        var a = a?.[function f() {
+            f(a);
+        }];
+        console.log(typeof f);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+issue_4947_1: {
+    options = {
+        conditionals: true,
+    }
+    input: {
+        console.log(console.foo ? 42..p : console.bar?.p);
+    }
+    expect: {
+        console.log(console.foo ? 42..p : console.bar?.p);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=14"
+}
+
+issue_4947_2: {
+    options = {
+        conditionals: true,
+    }
+    input: {
+        var log = console.log, fail;
+        log("PASS") ? log(42) : fail?.(42);
+    }
+    expect: {
+        var log = console.log, fail;
+        log("PASS") ? log(42) : fail?.(42);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+issue_5039: {
+    options = {
+        ie: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = a?.[function f() {
+            f;
+            a;
+        }];
+        console.log("PASS");
+    }
+    expect: {
+        var a = a?.[function f() {}];
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+issue_5091: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        function f(a) {
+            var b = a.p;
+            var c;
+            b?.[c = "FAIL 2"];
+            return b || c;
+        }
+        console.log(f("FAIL 1") || "PASS");
+    }
+    expect: {
+        function f(a) {
+            var a = a.p;
+            var c;
+            a?.[c = "FAIL 2"];
+            return a || c;
+        }
+        console.log(f("FAIL 1") || "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+issue_5292_dot: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        var o = {
+            get p() {
+                console.log("PASS");
+            }
+        };
+        o?.p;
+    }
+    expect: {
+        var o = {
+            get p() {
+                console.log("PASS");
+            }
+        };
+        o?.p;
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+issue_5292_dot_pure_getters: {
+    options = {
+        pure_getters: true,
+        side_effects: true,
+    }
+    input: {
+        var o = {
+            get p() {
+                console.log("PASS");
+            }
+        };
+        o?.p;
+    }
+    expect: {
+        var o = {
+            get p() {
+                console.log("PASS");
+            }
+        };
+    }
+}
+
+issue_5292_dot_pure_getters_strict: {
+    options = {
+        pure_getters: "strict",
+        side_effects: true,
+    }
+    input: {
+        var o = {
+            get p() {
+                console.log("PASS");
+            }
+        };
+        o?.p;
+    }
+    expect: {
+        var o = {
+            get p() {
+                console.log("PASS");
+            }
+        };
+        o?.p;
+    }
+    expect_stdout: "PASS"
+    node_version: ">=14"
+}
+
+issue_5292_sub: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        var o = {
+            get p() {
+                console.log("foo");
+            }
+        };
+        o?.[console.log("bar"), "p"];
+    }
+    expect: {
+        var o = {
+            get p() {
+                console.log("foo");
+            }
+        };
+        o?.[console.log("bar"), "p"];
+    }
+    expect_stdout: [
+        "bar",
+        "foo",
+    ]
+    node_version: ">=14"
+}
+
+issue_5292_sub_pure_getters: {
+    options = {
+        pure_getters: true,
+        side_effects: true,
+    }
+    input: {
+        var o = {
+            get p() {
+                console.log("foo");
+            }
+        };
+        o?.[console.log("bar"), "p"];
+    }
+    expect: {
+        var o = {
+            get p() {
+                console.log("foo");
+            }
+        };
+        console.log("bar");
+    }
+}
+
+issue_5292_sub_pure_getters_strict: {
+    options = {
+        pure_getters: "strict",
+        side_effects: true,
+    }
+    input: {
+        var o = {
+            get p() {
+                console.log("foo");
+            }
+        };
+        o?.[console.log("bar"), "p"];
+    }
+    expect: {
+        var o = {
+            get p() {
+                console.log("foo");
+            }
+        };
+        o?.[console.log("bar"), "p"];
+    }
+    expect_stdout: [
+        "bar",
+        "foo",
+    ]
+    node_version: ">=14"
+}
--- a/test/compress/properties.js
+++ b/test/compress/properties.js
@@ -17,7 +17,7 @@ dot_properties: {
        properties: true,
    }
    beautify = {
-        ie8: true,
+        ie: true,
    }
    input: {
        a["foo"] = "bar";
@@ -43,7 +43,7 @@ dot_properties_es5: {
        properties: true,
    }
    beautify = {
-        ie8: false,
+        ie: false,
    }
    input: {
        a["foo"] = "bar";
@@ -1400,3 +1400,181 @@ object_super: {
    expect_stdout: "PASS"
    node_version: ">=4"
 }
+
+issue_4831_1: {
+    options = {
+        properties: true,
+    }
+    input: {
+        console.log({
+            f() {
+                return arguments;
+            },
+        }.f("PASS")[0]);
+    }
+    expect: {
+        console.log([
+            function() {
+                return arguments;
+            },
+        ][0]("PASS")[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_4831_2: {
+    options = {
+        properties: true,
+    }
+    input: {
+        var f = {
+            f() {
+                return arguments;
+            },
+        }.f;
+        console.log(f("PASS")[0]);
+    }
+    expect: {
+        var f = {
+            f() {
+                return arguments;
+            },
+        }.f;
+        console.log(f("PASS")[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_4888: {
+    options = {
+        properties: true,
+    }
+    input: {
+        console.log(typeof {
+            __proto__: 42,
+        }.__proto__);
+    }
+    expect: {
+        console.log(typeof {
+            __proto__: 42,
+        }.__proto__);
+    }
+    expect_stdout: "object"
+}
+
+issue_5093: {
+    beautify = {
+        keep_quoted_props: true,
+    }
+    input: {
+        console.log({
+            a: true,
+            '42': "PASS",
+            "null": [],
+        }[6 * 7]);
+    }
+    expect_exact: 'console.log({a:true,"42":"PASS","null":[]}[6*7]);'
+    expect_stdout: "PASS"
+}
+
+issue_5093_quote_keys: {
+    beautify = {
+        keep_quoted_props: true,
+        quote_keys: true,
+    }
+    input: {
+        console.log({
+            a: true,
+            '42': "PASS",
+            "null": [],
+        }[6 * 7]);
+    }
+    expect_exact: 'console.log({"a":true,"42":"PASS","null":[]}[6*7]);'
+    expect_stdout: "PASS"
+}
+
+issue_5093_quote_style: {
+    beautify = {
+        keep_quoted_props: true,
+        quote_style: 3,
+    }
+    input: {
+        console.log({
+            a: true,
+            '42': "PASS",
+            "null": [],
+        }[6 * 7]);
+    }
+    expect_exact: 'console.log({a:true,\'42\':"PASS","null":[]}[6*7]);'
+    expect_stdout: "PASS"
+}
+
+object_methods: {
+    options = {
+        properties: true,
+    }
+    input: {
+        ({
+            p() {
+                console.log("FAIL 1");
+            },
+            *q() {
+                console.log("FAIL 2");
+            },
+            async r() {
+                console.log("FAIL 3");
+            },
+            async *s() {
+                console.log("PASS");
+            },
+        }).s().next();
+    }
+    expect: {
+        [
+            () => {
+                console.log("FAIL 1");
+            },
+            function*() {
+                console.log("FAIL 2");
+            },
+            async () => {
+                console.log("FAIL 3");
+            },
+            async function*() {
+                console.log("PASS");
+            },
+        ][3]().next();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=10"
+}
+
+issue_5177: {
+    options = {
+        properties: true,
+    }
+    input: {
+        var a = "FAIL";
+        var o = { a: "PASS" };
+        o.p = {
+            q() {
+                return this.a;
+            },
+        }.q;
+        console.log(o.p());
+    }
+    expect: {
+        var a = "FAIL";
+        var o = { a: "PASS" };
+        o.p = {
+            q() {
+                return this.a;
+            },
+        }.q;
+        console.log(o.p());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
--- a/test/compress/pure_funcs.js
+++ b/test/compress/pure_funcs.js
@@ -133,7 +133,7 @@ conditional: {
 relational: {
    options = {
        pure_funcs: [ "foo" ],
-        side_effects :true,
+        side_effects: true,
    }
    input: {
        foo() in new foo();
@@ -158,7 +158,7 @@ relational: {
 arithmetic: {
    options = {
        pure_funcs: [ "foo" ],
-        side_effects :true,
+        side_effects: true,
    }
    input: {
        foo() + foo();
@@ -183,7 +183,7 @@ arithmetic: {
 boolean_and: {
    options = {
        pure_funcs: [ "foo" ],
-        side_effects :true,
+        side_effects: true,
    }
    input: {
        foo() && foo();
@@ -208,7 +208,7 @@ boolean_and: {
 boolean_or: {
    options = {
        pure_funcs: [ "foo" ],
-        side_effects :true,
+        side_effects: true,
    }
    input: {
        foo() || foo();
@@ -233,7 +233,7 @@ boolean_or: {
 assign: {
    options = {
        pure_funcs: [ "foo" ],
-        side_effects :true,
+        side_effects: true,
    }
    input: {
        var a;
@@ -256,7 +256,7 @@ assign: {
 unary: {
    options = {
        pure_funcs: [ "foo" ],
-        side_effects :true,
+        side_effects: true,
    }
    input: {
        typeof foo();
--- a/test/compress/pure_getters.js
+++ b/test/compress/pure_getters.js
@@ -1320,6 +1320,7 @@ issue_2878: {

 issue_3427: {
    options = {
+        assignments: true,
        evaluate: true,
        inline: true,
        pure_getters: "strict",
@@ -1362,9 +1363,8 @@ issue_3490_1: {
    }
    expect: {
        var b = 42, c = "FAIL";
-        if (function() {
-            var a;
-        }(), c = "PASS", b) while ("" == typeof d);
+        var a;
+        if (c = "PASS", b) while ("" == typeof d);
        console.log(c, b);
    }
    expect_stdout: "PASS 42"
@@ -1564,3 +1564,123 @@ issue_4803: {
    }
    expect_stdout: "PASS"
 }
+
+nested_property_assignments_1: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var f;
+        ((f = function() {
+            console.log("FAIL");
+        }).p = f).q = console.log("PASS");
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+nested_property_assignments_2: {
+    options = {
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        var o = {};
+        (function() {
+            var a;
+            (o.p = a = {}).q = "PASS";
+        })();
+        console.log(o.p.q);
+    }
+    expect: {
+        var o = {};
+        (function() {
+            (o.p = {}).q = "PASS";
+        })();
+        console.log(o.p.q);
+    }
+    expect_stdout: "PASS"
+}
+
+nested_property_assignments_3: {
+    options = {
+        collapse_vars: true,
+        pure_getters: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var o = { p: {} };
+        (function(a) {
+            console && a;
+            if (console) {
+                a = a.p;
+                a.q = a;
+            }
+        })(o);
+        console.log(o.p.q === o.p ? "PASS" : "FAIL");
+    }
+    expect: {
+        var o = { p: {} };
+        (function(a) {
+            console;
+            if (console)
+                (a = a.p).q = a;
+        })(o);
+        console.log(o.p.q === o.p ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+}
+
+nested_property_assignments_4: {
+    options = {
+        pure_getters: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var n, o = { p: { q: { r: "PASS" } } };
+        (n = o.p).r = n.q.r;
+        console.log(o.p.r);
+    }
+    expect: {
+        var n, o = { p: { q: { r: "PASS" } } };
+        (n = o.p).r = n.q.r;
+        console.log(o.p.r);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4939: {
+    options = {
+        pure_getters: "strict",
+        side_effects: true,
+    }
+    input: {
+        ({
+            __proto__: {
+                get p() {
+                    console.log("PASS");
+                },
+            },
+        }).p;
+    }
+    expect: {
+        ({
+            __proto__: {
+                get p() {
+                    console.log("PASS");
+                },
+            },
+        }).p;
+    }
+    expect_stdout: "PASS"
+}
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -41,10 +41,8 @@ reduce_vars: {
    }
    expect: {
        var A = 1;
-        (function() {
-            console.log(-3);
-            console.log(A - 5);
-        })();
+        console.log(-3);
+        console.log(A - 5);
        (function f1() {
            var a = 2;
            console.log(a - 5);
@@ -905,7 +903,7 @@ use_before_var: {
    }
    expect: {
        function f(){
-            console.log(void 0);
+            console.log(t);
            var t = 1;
        }
    }
@@ -981,7 +979,7 @@ inner_var_for_1: {
    expect: {
        function f() {
            var a = 1;
-            x(1, void 0, d);
+            x(1, b, d);
            for (var b = 2, c = 3; x(1, 2, 3, d); x(1, 2, 3, d)) {
                var d = 4, e = 5;
                x(1, 2, 3, d, e);
@@ -1292,6 +1290,7 @@ toplevel_on_loops_3: {
        loops: true,
        reduce_funcs: true,
        reduce_vars: true,
+        side_effects: true,
        toplevel: true,
        unused: true,
    }
@@ -2071,72 +2070,6 @@ issue_1670_2: {
 }

 issue_1670_3: {
-    options = {
-        comparisons: true,
-        conditionals: true,
-        dead_code: true,
-        evaluate: true,
-        reduce_funcs: true,
-        reduce_vars: true,
-        side_effects: true,
-        switches: true,
-        typeofs: true,
-        unused: true,
-    }
-    input: {
-        (function f() {
-            switch (1) {
-              case 0:
-                var a = true;
-                break;
-              case 1:
-                if (typeof a === "undefined") console.log("PASS");
-                else console.log("FAIL");
-            }
-        })();
-    }
-    expect: {
-        (function() {
-            var a;
-            void 0 === a ? console.log("PASS") : console.log("FAIL");
-        })();
-    }
-    expect_stdout: "PASS"
-}
-
-issue_1670_4: {
-    options = {
-        conditionals: true,
-        dead_code: true,
-        evaluate: true,
-        passes: 2,
-        reduce_funcs: true,
-        reduce_vars: true,
-        side_effects: true,
-        switches: true,
-        unused: true,
-    }
-    input: {
-        (function f() {
-            switch (1) {
-              case 0:
-                var a = true;
-                break;
-              case 1:
-                if (typeof a === "undefined") console.log("PASS");
-                else console.log("FAIL");
-            }
-        })();
-    }
-    expect: {
-        (function() {
-            console.log("PASS");
-        })();
-    }
-    expect_stdout: "PASS"
-}
-
-issue_1670_5: {
    options = {
        conditionals: true,
        dead_code: true,
@@ -2168,7 +2101,7 @@ issue_1670_5: {
    expect_stdout: "1"
 }

-issue_1670_6: {
+issue_1670_4: {
    options = {
        conditionals: true,
        dead_code: true,
@@ -3158,7 +3091,7 @@ accessor_1: {
                a = 2;
                return a;
            },
-            b: 1
+            b: 1,
        }.b, a);
    }
    expect: {
@@ -3168,7 +3101,7 @@ accessor_1: {
                a = 2;
                return a;
            },
-            b: 1
+            b: 1,
        }.b, a);
    }
    expect_stdout: "1 1"
@@ -3188,7 +3121,7 @@ accessor_2: {
        var B = {
            get c() {
                console.log(A);
-            }
+            },
        };
        B.c;
    }
@@ -3196,7 +3129,7 @@ accessor_2: {
        ({
            get c() {
                console.log(1);
-            }
+            },
        }).c;
    }
    expect_stdout: "1"
@@ -3242,7 +3175,7 @@ obj_var_1: {
        var obj = {
            bar: function() {
                return C + C;
-            }
+            },
        };
        console.log(obj.bar());
    }
@@ -3250,7 +3183,7 @@ obj_var_1: {
        console.log({
            bar: function() {
                return 2;
-            }
+            },
        }.bar());
    }
    expect_stdout: "2"
@@ -3274,7 +3207,7 @@ obj_var_2: {
        var obj = {
            bar: function() {
                return C + C;
-            }
+            },
        };
        console.log(obj.bar());
    }
@@ -4488,6 +4421,7 @@ perf_2: {

 perf_3: {
    options = {
+        passes: 2,
        reduce_funcs: true,
        reduce_vars: true,
        toplevel: true,
@@ -4496,10 +4430,10 @@ perf_3: {
    input: {
        var foo = function(x, y, z) {
            return x < y ? x * y + z : x * z - y;
-        }
+        };
        var indirect_foo = function(x, y, z) {
            return foo(x, y, z);
-        }
+        };
        var sum = 0;
        for (var i = 0; i < 100; ++i)
            sum += indirect_foo(i, i + 1, 3 * i);
@@ -4528,10 +4462,10 @@ perf_4: {
    input: {
        var foo = function(x, y, z) {
            return x < y ? x * y + z : x * z - y;
-        }
+        };
        var indirect_foo = function(x, y, z) {
            return foo(x, y, z);
-        }
+        };
        var sum = 0;
        for (var i = 0; i < 100; ++i)
            sum += indirect_foo(i, i + 1, 3 * i);
@@ -4540,10 +4474,10 @@ perf_4: {
    expect: {
        var foo = function(x, y, z) {
            return x < y ? x * y + z : x * z - y;
-        }
+        };
        var indirect_foo = function(x, y, z) {
            return foo(x, y, z);
-        }
+        };
        var sum = 0;
        for (var i = 0; i < 100; ++i)
            sum += indirect_foo(i, i + 1, 3 * i);
@@ -4632,9 +4566,9 @@ perf_7: {
        var indirect_foo = function(x, y, z) {
            var foo = function(x, y, z) {
                return x < y ? x * y + z : x * z - y;
-            }
+            };
            return foo(x, y, z);
-        }
+        };
        var sum = 0;
        for (var i = 0; i < 100; ++i)
            sum += indirect_foo(i, i + 1, 3 * i);
@@ -4664,9 +4598,9 @@ perf_8: {
        var indirect_foo = function(x, y, z) {
            var foo = function(x, y, z) {
                return x < y ? x * y + z : x * z - y;
-            }
+            };
            return foo(x, y, z);
-        }
+        };
        var sum = 0;
        for (var i = 0; i < 100; ++i)
            sum += indirect_foo(i, i + 1, 3 * i);
@@ -4677,7 +4611,7 @@ perf_8: {
            return function(x, y, z) {
                return x < y ? x * y + z : x * z - y;
            }(x, y, z);
-        }
+        };
        var sum = 0;
        for (var i = 0; i < 100; ++i)
            sum += indirect_foo(i, i + 1, 3 * i);
@@ -6735,6 +6669,7 @@ issues_3267_1: {
        dead_code: true,
        evaluate: true,
        inline: true,
+        negate_iife: true,
        reduce_vars: true,
        sequences: true,
        side_effects: true,
@@ -6752,8 +6687,9 @@ issues_3267_1: {
        });
    }
    expect: {
-        !function(i) {
-            if (Object())
+        !function(x) {
+            var i = Object();
+            if (i)
                return console.log("PASS");
            throw "FAIL";
        }();
@@ -6769,6 +6705,7 @@ issues_3267_2: {
        evaluate: true,
        inline: true,
        keep_fargs: false,
+        negate_iife: true,
        passes: 2,
        reduce_vars: true,
        sequences: true,
@@ -7384,6 +7321,64 @@ local_assignment_loop: {
    expect_stdout: "PASS"
 }

+local_assignment_modified: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        var a;
+        (a = a || {}).p = 42;
+        console.log(a.p);
+    }
+    expect: {
+        var a;
+        (a = {}).p = 42;
+        console.log(a.p);
+    }
+    expect_stdout: "42"
+}
+
+local_declaration: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        var a;
+        a || console.log(a = "PASS");
+    }
+    expect: {
+        var a;
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+local_definition_modified: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        var a = a || {};
+        a.p = 42;
+        console.log(a.p);
+    }
+    expect: {
+        var a = {};
+        a.p = 42;
+        console.log(a.p);
+    }
+    expect_stdout: "42"
+}
+
 issue_3957_1: {
    options = {
        evaluate: true,
@@ -7499,6 +7494,7 @@ issue_4030: {
        collapse_vars: true,
        evaluate: true,
        reduce_vars: true,
+        side_effects: true,
        toplevel: true,
        unused: true,
    }
@@ -7631,3 +7627,208 @@ issue_4568: {
    }
    expect_stdout: "PASS"
 }
+
+issue_4937: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            while (console.log("PASS"));
+        }
+        do {
+            function g() {
+                f();
+            }
+        } while (!g);
+        f();
+    }
+    expect: {
+        function f() {
+            while (console.log("PASS"));
+        }
+        do {
+            function g() {
+                f();
+            }
+        } while (!g);
+        f();
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4943_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a, b = 1;
+        (function f() {
+            a = "foo";
+            b-- && f();
+            console.log(a);
+            a = "bar";
+        })();
+    }
+    expect: {
+        var a, b = 1;
+        (function f() {
+            a = "foo";
+            b-- && f();
+            console.log(a);
+            a = "bar";
+        })();
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+}
+
+issue_4943_2: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a, b = 1;
+        (function f() {
+            a = "foo";
+            b-- && f();
+            console.log(a);
+            a = "bar";
+        })();
+    }
+    expect: {
+        var a, b = 1;
+        (function f() {
+            a = "foo";
+            b-- && f();
+            console.log(a);
+            a = "bar";
+        })();
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+}
+
+issue_4949: {
+    options = {
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function f(a) {
+            a = 0;
+            console.log(a++, arguments[0]);
+        })(0);
+    }
+    expect: {
+        (function(a) {
+            a = 0;
+            console.log(a++, arguments[0]);
+        })(0);
+    }
+    expect_stdout: "0 1"
+}
+
+issue_5048: {
+    options = {
+        reduce_funcs: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var a = function() {
+                return a + 42;
+            };
+        }());
+    }
+    expect: {
+        console.log(function() {}());
+    }
+    expect_stdout: "undefined"
+}
+
+issue_5050: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        function f() {
+            console.log(a);
+        }
+        this;
+        var a = 1;
+        f(console.log(2), f(), a = 3);
+    }
+    expect: {
+        function f() {
+            console.log(a);
+        }
+        this;
+        var a = 1;
+        f(console.log(2), f(), a = 3);
+    }
+    expect_stdout: [
+        "2",
+        "1",
+        "3",
+    ]
+}
+
+issue_5055_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = "PASS";
+        function f() {
+            console.log(a || "FAIL");
+        }
+        f(0 && (a = 0)(f(this)));
+    }
+    expect: {
+        var a = "PASS";
+        function f() {
+            console.log(a || "FAIL");
+        }
+        f(0);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5055_2: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        function f() {
+            console.log(a || "FAIL");
+        }
+        f(0 && (a = 0)(f(this)));
+    }
+    expect: {
+        var a = "PASS";
+        function f() {
+            console.log(a || "FAIL");
+        }
+        f(0 && (a = 0)(f()));
+    }
+    expect_stdout: "PASS"
+}
--- a/test/compress/rename.js
+++ b/test/compress/rename.js
@@ -1,11 +1,11 @@
 mangle_catch: {
    rename = true
    options = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -24,11 +24,11 @@ mangle_catch: {
 mangle_catch_ie8: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -47,11 +47,11 @@ mangle_catch_ie8: {
 mangle_catch_var: {
    rename = true
    options = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -70,11 +70,11 @@ mangle_catch_var: {
 mangle_catch_var_ie8: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -93,11 +93,11 @@ mangle_catch_var_ie8: {
 mangle_catch_toplevel: {
    rename = true
    options = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -116,11 +116,11 @@ mangle_catch_toplevel: {
 mangle_catch_ie8_toplevel: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -139,11 +139,11 @@ mangle_catch_ie8_toplevel: {
 mangle_catch_var_toplevel: {
    rename = true
    options = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -162,11 +162,11 @@ mangle_catch_var_toplevel: {
 mangle_catch_var_ie8_toplevel: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -185,11 +185,11 @@ mangle_catch_var_ie8_toplevel: {
 mangle_catch_redef_1: {
    rename = true
    options = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -208,11 +208,11 @@ mangle_catch_redef_1: {
 mangle_catch_redef_1_ie8: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -231,11 +231,11 @@ mangle_catch_redef_1_ie8: {
 mangle_catch_redef_1_toplevel: {
    rename = true
    options = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -254,11 +254,11 @@ mangle_catch_redef_1_toplevel: {
 mangle_catch_redef_1_ie8_toplevel: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -277,11 +277,11 @@ mangle_catch_redef_1_ie8_toplevel: {
 mangle_catch_redef_2: {
    rename = true
    options = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -299,11 +299,11 @@ mangle_catch_redef_2: {
 mangle_catch_redef_2_ie8: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -321,11 +321,11 @@ mangle_catch_redef_2_ie8: {
 mangle_catch_redef_2_toplevel: {
    rename = true
    options = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -343,11 +343,11 @@ mangle_catch_redef_2_toplevel: {
 mangle_catch_redef_2_ie8_toplevel: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -365,7 +365,7 @@ mangle_catch_redef_2_ie8_toplevel: {
 issue_2120_1: {
    rename = true
    mangle = {
-        ie8: false,
+        ie: false,
    }
    input: {
        "aaaaaaaa";
@@ -401,7 +401,7 @@ issue_2120_1: {
 issue_2120_2: {
    rename = true
    mangle = {
-        ie8: true,
+        ie: true,
    }
    input: {
        "aaaaaaaa";
@@ -436,7 +436,7 @@ issue_2120_2: {
 function_iife_catch: {
    rename = true
    mangle = {
-        ie8: false,
+        ie: false,
    }
    input: {
        function f(n) {
@@ -458,7 +458,7 @@ function_iife_catch: {
 function_iife_catch_ie8: {
    rename = true
    mangle = {
-        ie8: true,
+        ie: true,
    }
    input: {
        function f(n) {
@@ -480,7 +480,7 @@ function_iife_catch_ie8: {
 function_catch_catch: {
    rename = true
    mangle = {
-        ie8: false,
+        ie: false,
    }
    input: {
        var o = 0;
@@ -509,7 +509,7 @@ function_catch_catch: {
 function_catch_catch_ie8: {
    rename = true
    mangle = {
-        ie8: true,
+        ie: true,
    }
    input: {
        var o = 0;
@@ -538,12 +538,12 @@ function_catch_catch_ie8: {
 function_do_catch_ie8: {
    rename = true
    options = {
-        ie8: true,
+        ie: true,
        side_effects: true,
        unused: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -615,7 +615,7 @@ function_do_catch_ie8: {
 issue_3480: {
    rename = true,
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: false,
    }
    input: {
@@ -647,7 +647,7 @@ issue_3480: {
 issue_3480_ie8: {
    rename = true,
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: false,
    }
    input: {
@@ -679,7 +679,7 @@ issue_3480_ie8: {
 issue_3480_toplevel: {
    rename = true,
    mangle = {
-        ie8: false,
+        ie: false,
        toplevel: true,
    }
    input: {
@@ -711,7 +711,7 @@ issue_3480_toplevel: {
 issue_3480_ie8_toplevel: {
    rename = true,
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
--- a/test/compress/rests.js
+++ b/test/compress/rests.js
@@ -51,7 +51,7 @@ arrow_destructured_object_1: {
    }
    expect_exact: "var f=({...a})=>a,o=f({PASS:42});for(var k in o)console.log(k,o[k]);"
    expect_stdout: "PASS 42"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 arrow_destructured_object_2: {
@@ -62,7 +62,7 @@ arrow_destructured_object_2: {
    }
    expect_exact: "var f=({FAIL:a,...b})=>b,o=f({PASS:42,FAIL:null});for(var k in o)console.log(k,o[k]);"
    expect_stdout: "PASS 42"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 arrow_destructured_object_3: {
@@ -79,7 +79,7 @@ arrow_destructured_object_3: {
        "2 S",
        "3 S",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 funarg_1: {
@@ -131,7 +131,7 @@ destructured_object_1: {
    }
    expect_exact: 'var{...a}=["FAIL","PASS",42];console.log(a[1],a[2]);'
    expect_stdout: "PASS 42"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 destructured_object_2: {
@@ -141,7 +141,7 @@ destructured_object_2: {
    }
    expect_exact: 'var{0:a,...b}=["FAIL","PASS",42];console.log(b[1],b[2]);'
    expect_stdout: "PASS 42"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 drop_fargs: {
@@ -231,7 +231,7 @@ reduce_destructured_object: {
        console.log(a[0]);
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 retain_destructured_array: {
@@ -244,7 +244,7 @@ retain_destructured_array: {
        console.log.apply(console, b);
    }
    expect: {
-        var [ , ...b ] = [ "FAIL", "PASS", 42 ];
+        var [ ...b ] = [ "PASS", 42 ];
        console.log.apply(console, b);
    }
    expect_stdout: "PASS 42"
@@ -270,7 +270,7 @@ retain_destructured_object_1: {
        "1 PASS",
        "2 42",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 retain_destructured_object_2: {
@@ -284,7 +284,7 @@ retain_destructured_object_2: {
            console.log(k, b[k]);
    }
    expect: {
-        var { foo: [], ...b } = { foo: [ "FAIL" ], bar: "PASS", baz: 42 };
+        var { foo: {}, ...b } = { foo: 0, bar: "PASS", baz: 42 };
        for (var k in b)
            console.log(k, b[k]);
    }
@@ -292,7 +292,7 @@ retain_destructured_object_2: {
        "bar PASS",
        "baz 42",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 retain_funarg_destructured_array_1: {
@@ -344,7 +344,7 @@ retain_funarg_destructured_object_1: {
        console.log((({ ...a }) => a)([ "PASS" ])[0]);
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 retain_funarg_destructured_object_2: {
@@ -359,10 +359,10 @@ retain_funarg_destructured_object_2: {
    expect: {
        console.log(function({ p: a, ... b }) {
            return b;
-        }({ p: "FAIL" }).p || "PASS");
+        }({}).p || "PASS");
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 drop_unused_call_args_1: {
@@ -407,6 +407,24 @@ drop_unused_call_args_2: {
    node_version: ">=6"
 }

+maintain_position: {
+    options = {
+        unused: true,
+    }
+    input: {
+        A = "FAIL";
+        var [ , ...a ] = [ A, "PASS" ];
+        console.log(a[0]);
+    }
+    expect: {
+        A = "FAIL";
+        var [ , ...a ] = [ A, "PASS" ];
+        console.log(a[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 merge_funarg: {
    options = {
        merge_vars: true,
@@ -418,9 +436,9 @@ merge_funarg: {
        })();
    }
    expect: {
-        (function(...b) {
-            var b = b.length;
-            console.log(b);
+        (function(...a) {
+            var a = a.length;
+            console.log(a);
        })();
    }
    expect_stdout: "0"
@@ -438,9 +456,9 @@ merge_funarg_destructured_array: {
        })([]);
    }
    expect: {
-        (function([ ...b ]) {
-            var b = b.length;
-            console.log(b);
+        (function([ ...a ]) {
+            var a = a.length;
+            console.log(a);
        })([]);
    }
    expect_stdout: "0"
@@ -458,13 +476,13 @@ merge_funarg_destructured_object: {
        })([ "PASS" ]);
    }
    expect: {
-        (function({ ...b }) {
-            var b = b[0];
-            console.log(b);
+        (function({ ...a }) {
+            var a = a[0];
+            console.log(a);
        })([ "PASS" ]);
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 keep_arguments: {
@@ -491,7 +509,7 @@ drop_rest_array: {
        rests: true,
    }
    input: {
-        var [ ...[ a ]] = [ "PASS" ];
+        var [ ...[ a ] ] = [ "PASS" ];
        console.log(a);
    }
    expect: {
@@ -542,6 +560,100 @@ drop_rest_lambda: {
    node_version: ">=6"
 }

+keep_rest_array: {
+    options = {
+        rests: true,
+    }
+    input: {
+        var [ ...[ ...a ] ] = "PASS";
+        console.log(a.join(""));
+    }
+    expect: {
+        var [ ...a ] = "PASS";
+        console.log(a.join(""));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+keep_rest_arrow: {
+    options = {
+        arrows: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        rests: true,
+    }
+    input: {
+        console.log(((...[ ...a ]) => a.join(""))("PASS"));
+    }
+    expect: {
+        console.log(((...a) => a.join(""))("PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+keep_rest_lambda_1: {
+    options = {
+        keep_fargs: false,
+        reduce_vars: true,
+        rests: true,
+        toplevel: true,
+    }
+    input: {
+        function f(...[ ...a ]) {
+            return a.join("");
+        }
+        console.log(f("PASS"), f([ 42 ]));
+    }
+    expect: {
+        function f(...a) {
+            return a.join("");
+        }
+        console.log(f("PASS"), f([ 42 ]));
+    }
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+keep_rest_lambda_2: {
+    options = {
+        unused: true,
+    }
+    input: {
+        function f(...[ ...a ]) {
+            return a.join("");
+        }
+        console.log(f("PASS"), f([ 42 ]));
+    }
+    expect: {
+        function f(...[ ...a ]) {
+            return a.join("");
+        }
+        console.log(f("PASS"), f([ 42 ]));
+    }
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+drop_new_function: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        new function(...{
+            [console.log("PASS")]: a,
+        }) {}();
+    }
+    expect: {
+        void ([ ... {
+            [console.log("PASS")]: [].e,
+        }] = []);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 issue_4525_1: {
    options = {
        arguments: true,
@@ -647,6 +759,78 @@ issue_4544_2: {
    node_version: ">=6"
 }

+issue_4560_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 0;
+        (function(...{
+            [a++]: {},
+        }) {})(2);
+        console.log(a);
+    }
+    expect: {
+        var a = 0;
+        (function(...{
+            [a++]: {},
+        }) {})(2);
+        console.log(a);
+    }
+    expect_stdout: "1"
+    node_version: ">=6"
+}
+
+issue_4560_2: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = 0;
+        (function(...{
+            [a++]: {},
+        }) {})(2);
+        console.log(a);
+    }
+    expect: {
+        var a = 0;
+        (function(...{
+            [a++]: {},
+        }) {})(2);
+        console.log(a);
+    }
+    expect_stdout: "1"
+    node_version: ">=6"
+}
+
+issue_4560_3: {
+    options = {
+        collapse_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 0, b;
+        [ ...{
+            [a++]: b,
+        } ] = [ "PASS" ];
+        console.log(b);
+    }
+    expect: {
+        var a = 0, b;
+        [ ...{
+            [a++]: b,
+        } ] = [ "PASS" ];
+        console.log(b);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 issue_4562: {
    options = {
        evaluate: true,
@@ -667,7 +851,7 @@ issue_4562: {
 issue_4575: {
    options = {
        collapse_vars: true,
-        ie8: true,
+        ie: true,
        reduce_vars: true,
        rests: true,
        unused: true,
@@ -682,9 +866,9 @@ issue_4575: {
    }
    expect: {
        (function(a) {
-            (function a(...d) {
+            (function(d) {
                console.log(d.length);
-            })();
+            })([]);
        })();
    }
    expect_stdout: "0"
@@ -777,10 +961,306 @@ issue_4666: {
    expect: {
        var a = 0, b = 0;
        var o = (c => +a + c)([ b ]);
-        for(var k in o)
+        for (var k in o)
            b++;
        console.log(1, b);
    }
    expect_stdout: "1 2"
    node_version: ">=6"
 }
+
+issue_5089_1: {
+    options = {
+        unused: true,
+    }
+    input: {
+        var {
+            p: [] = 42,
+            ...o
+        } = {
+            p: [],
+        };
+        console.log(o.p);
+    }
+    expect: {
+        var {
+            p: {},
+            ...o
+        } = {
+            p: 0,
+        };
+        console.log(o.p);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=8.3.0"
+}
+
+issue_5089_2: {
+    options = {
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        var {
+            p: {} = null,
+            ...o
+        } = {
+            p: {},
+        };
+        console.log(o.p);
+    }
+    expect: {
+        var {
+            p: {},
+            ...o
+        } = {
+            p: 0,
+        };
+        console.log(o.p);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=8.3.0"
+}
+
+issue_5100_1: {
+    options = {
+        passes: 2,
+        pure_getters: "strict",
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        [ {
+            p: {},
+            ...a
+        } ] = [ {
+            p: {
+                q: a,
+            } = 42,
+            r: "PASS",
+        } ];
+        console.log(a.r);
+    }
+    expect: {
+        var a;
+        ({
+            p: {},
+            ...a
+        } = [ {
+            p: [ a = 42["q"] ],
+            r: "PASS",
+        } ][0]);
+        console.log(a.r);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8.3.0"
+}
+
+issue_5100_2: {
+    options = {
+        passes: 2,
+        pure_getters: "strict",
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        [ {
+            p: {},
+            ...a
+        } ] = [ {
+            p: (console.log("PASS"), {
+                q: a,
+            } = 42),
+        } ];
+    }
+    expect: {
+        var a;
+        ({
+            p: {},
+            ...a
+        } = [ {
+            p: [ console.log("PASS"), a = 42["q"] ],
+        } ][0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=10.22.0"
+}
+
+issue_5108: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        rests: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        console.log(function([ ...[ a ] ]) {
+            return a;
+        }([ "PASS", "FAIL" ]));
+    }
+    expect: {
+        console.log(function([]) {
+            return "PASS";
+        }([]));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5128_1: {
+    options = {
+        inline: true,
+    }
+    input: {
+        console.log(function() {
+            return function f(...[ a ]) {
+                return a;
+            }("PASS");
+        }());
+    }
+    expect: {
+        console.log(function f(...[ a ]) {
+            return a;
+        }("PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5128_2: {
+    options = {
+        inline: true,
+        keep_fnames: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            return function f(...[ a ]) {
+                return a;
+            }("PASS");
+        }());
+    }
+    expect: {
+        console.log(function f(...[ a ]) {
+            return a;
+        }("PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5165_1: {
+    options = {
+        conditionals: true,
+        dead_code: true,
+        evaluate: true,
+        reduce_vars: true,
+        rests: true,
+        side_effects: true,
+        switches: true,
+        unsafe: true,
+    }
+    input: {
+        console.log(function([ ...a ]) {
+            switch (a) {
+              case a:
+                return "PASS";
+            }
+        }([]));
+    }
+    expect: {
+        console.log(function([ ...a ]) {
+            return "PASS";
+        }([]));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5165_2: {
+    options = {
+        conditionals: true,
+        dead_code: true,
+        evaluate: true,
+        reduce_vars: true,
+        rests: true,
+        side_effects: true,
+        switches: true,
+        unsafe: true,
+    }
+    input: {
+        console.log(function(...a) {
+            switch (a) {
+              case a:
+                return "PASS";
+            }
+        }());
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5246_1: {
+    options = {
+        reduce_vars: true,
+        rests: true,
+        unused: true,
+    }
+    input: {
+        console.log(typeof function([ , ...a ]) {
+            return this && a;
+        }([ , function(){} ])[0]);
+    }
+    expect: {
+        console.log(typeof function([]) {
+            return this && [ function(){} ];
+        }([])[0]);
+    }
+    expect_stdout: "function"
+    node_version: ">=6"
+}
+
+issue_5246_2: {
+    options = {
+        reduce_vars: true,
+        rests: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        A = [ , "PASS", "FAIL" ];
+        var  [ , ...a ] = [ ... A ];
+        console.log(a[0]);
+    }
+    expect: {
+        A = [ , "PASS", "FAIL" ];
+        var  [ , ...a ] = [ ... A ];
+        console.log(a[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5246_3: {
+    options = {
+        unused: true,
+    }
+    input: {
+        (function f(...[ [ a ] ]) {
+            console.log(a);
+        })([ "PASS" ]);
+    }
+    expect: {
+        (function(...[ a ]) {
+            console.log(a);
+        })([ "PASS" ][0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
--- a/test/compress/sandbox.js
+++ b/test/compress/sandbox.js
@@ -172,3 +172,49 @@ issue_4054: {
    }
    expect_stdout: "{ p: [Setter] }"
 }
+
+issue_4811_1: {
+    input: {
+        for (var PASS in this);
+        console.log(PASS, this, {} < this);
+    }
+    expect: {
+        for (var PASS in this);
+        console.log(PASS, this, {} < this);
+    }
+    expect_stdout: "PASS [object global] true"
+}
+
+issue_4811_2: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        (async function() {});
+        for (var PASS in this);
+        console.log(PASS, this, {} < this);
+    }
+    expect: {
+        for (var PASS in this);
+        console.log(PASS, this, {} < this);
+    }
+    expect_stdout: "PASS [object global] true"
+    node_version: ">=8"
+}
+
+issue_5197: {
+    rename = true
+    input: {
+        function f(async) {
+            async(")=>{}");
+        }
+        console.log("" + this.__proto__);
+    }
+    expect: {
+        function f(a) {
+            a(")=>{}");
+        }
+        console.log("" + this.__proto__);
+    }
+    expect_stdout: "[object global]"
+}
--- a/test/compress/sequences.js
+++ b/test/compress/sequences.js
@@ -774,7 +774,7 @@ side_effects_cascade_3: {
    }
    expect: {
        function f(a, b) {
-            (b += a) || (b = a) || (b -= a, b ^= a),
+            (b += a) || (b = a) || (b = b - a ^ a),
            a--;
        }
    }
@@ -910,9 +910,7 @@ hoist_decl: {
        var d;
    }
    expect: {
-        var a;
-        w();
-        var b = x(), c, d;
+        var a, b = (w(), x()), c, d;
        for (y(); 0;) z();
    }
 }
@@ -1162,10 +1160,8 @@ issue_3490_1: {
    }
    expect: {
        var b = 42, c = "FAIL";
-        if (function() {
-            var a;
-            a && a.p;
-        }(), c = "PASS", b) while ("" == typeof d);
+        var a;
+        if (a && a.p, c = "PASS", b) while ("" == typeof d);
        console.log(c, b);
    }
    expect_stdout: "PASS 42"
@@ -1195,9 +1191,8 @@ issue_3490_2: {
    }
    expect: {
        var b = 42, c = "FAIL";
-        for (function() {
-            var a;
-        }(), c = "PASS", b; "" == typeof d;);
+        var a;
+        for (c = "PASS", b; "" == typeof d;);
        console.log(c, b);
    }
    expect_stdout: "PASS 42"
--- a/test/compress/side_effects.js
+++ b/test/compress/side_effects.js
@@ -198,6 +198,36 @@ global_fns: {
    ]
 }

+global_constructors: {
+    options = {
+        side_effects: true,
+        unsafe: true,
+    }
+    input: {
+        Map;
+        new Map(console.log("foo"));
+        Set;
+        new Set(console.log("bar"));
+        WeakMap;
+        new WeakMap(console.log("baz"));
+        WeakSet;
+        new WeakSet(console.log("moo"));
+    }
+    expect: {
+        console.log("foo");
+        console.log("bar");
+        console.log("baz");
+        console.log("moo");
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+        "baz",
+        "moo",
+    ]
+    node_version: ">=0.12"
+}
+
 unsafe_builtin_1: {
    options = {
        side_effects: true,
--- a/test/compress/spreads.js
+++ b/test/compress/spreads.js
@@ -147,7 +147,7 @@ dont_inline: {
    node_version: ">=6"
 }

-do_inline: {
+do_inline_1: {
    options = {
        inline: true,
        spreads: true,
@@ -164,6 +164,46 @@ do_inline: {
    node_version: ">=6"
 }

+do_inline_2: {
+    options = {
+        inline: true,
+        side_effects: true,
+    }
+    input: {
+        (function() {
+            (function() {
+                console.log("PASS");
+            })(..."");
+        })();
+    }
+    expect: {
+        [] = [ ..."" ],
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+do_inline_3: {
+    options = {
+        if_return: true,
+        inline: true,
+    }
+    input: {
+        (function() {
+            (function() {
+                while (console.log("PASS"));
+            })(..."");
+        })();
+    }
+    expect: {
+        var [] = [ ..."" ];
+        while (console.log("PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 drop_empty_call_1: {
    options = {
        side_effects: true,
@@ -201,7 +241,29 @@ drop_empty_call_2: {
    node_version: ">=6"
 }

-convert_hole: {
+convert_hole_array: {
+    options = {
+        spreads: true,
+    }
+    input: {
+        [ ...[ "PASS", , 42 ] ].forEach(function(a) {
+            console.log(a);
+        });
+    }
+    expect: {
+        [ "PASS", void 0, 42 ].forEach(function(a) {
+            console.log(a);
+        });
+    }
+    expect_stdout: [
+        "PASS",
+        "undefined",
+        "42",
+    ]
+    node_version: ">=6"
+}
+
+convert_hole_call: {
    options = {
        spreads: true,
    }
@@ -341,7 +403,7 @@ convert_setter: {
            console.log(k, o[k]);
    }
    expect_stdout: "PASS undefined"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 keep_getter_1: {
@@ -370,7 +432,7 @@ keep_getter_1: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 keep_getter_2: {
@@ -399,7 +461,7 @@ keep_getter_2: {
        "foo",
        "bar",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 keep_getter_3: {
@@ -429,7 +491,7 @@ keep_getter_3: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 keep_getter_4: {
@@ -460,7 +522,7 @@ keep_getter_4: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 keep_accessor: {
@@ -508,7 +570,7 @@ keep_accessor: {
        "q undefined",
        "r null",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 object_key_order_1: {
@@ -538,7 +600,7 @@ object_key_order_1: {
        "a 3",
        "b 2",
    ]
-    node_version: ">=8 <=10"
+    node_version: ">=8.3.0 <=10"
 }

 object_key_order_2: {
@@ -568,7 +630,7 @@ object_key_order_2: {
        "a 3",
        "b 2",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 object_key_order_3: {
@@ -598,7 +660,7 @@ object_key_order_3: {
        "a 3",
        "b 2",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 object_key_order_4: {
@@ -628,7 +690,7 @@ object_key_order_4: {
        "a 3",
        "b 2",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 object_spread_array: {
@@ -654,7 +716,7 @@ object_spread_array: {
        "0 foo",
        "1 bar",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 object_spread_string: {
@@ -681,7 +743,7 @@ object_spread_string: {
        "1 o",
        "2 o",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 unused_var_side_effects: {
@@ -711,7 +773,7 @@ unused_var_side_effects: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 unsafe_join_1: {
@@ -793,7 +855,7 @@ issue_4329: {
        }[0]);
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4331: {
@@ -871,7 +933,7 @@ issue_4345: {
        }[42]);
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4361: {
@@ -901,7 +963,7 @@ issue_4361: {
        "foo",
        "undefined",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4363: {
@@ -922,7 +984,7 @@ issue_4363: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4556: {
@@ -945,78 +1007,6 @@ issue_4556: {
    node_version: ">=6"
 }

-issue_4560_1: {
-    options = {
-        evaluate: true,
-        reduce_vars: true,
-        toplevel: true,
-    }
-    input: {
-        var a = 0;
-        (function(...{
-            [a++]: {},
-        }) {})(2);
-        console.log(a);
-    }
-    expect: {
-        var a = 0;
-        (function(...{
-            [a++]: {},
-        }) {})(2);
-        console.log(a);
-    }
-    expect_stdout: "1"
-    node_version: ">=6"
-}
-
-issue_4560_2: {
-    options = {
-        reduce_vars: true,
-        toplevel: true,
-        unused: true,
-    }
-    input: {
-        var a = 0;
-        (function(...{
-            [a++]: {},
-        }) {})(2);
-        console.log(a);
-    }
-    expect: {
-        var a = 0;
-        (function(...{
-            [a++]: {},
-        }) {})(2);
-        console.log(a);
-    }
-    expect_stdout: "1"
-    node_version: ">=6"
-}
-
-issue_4560_3: {
-    options = {
-        collapse_vars: true,
-        reduce_vars: true,
-        toplevel: true,
-    }
-    input: {
-        var a = 0, b;
-        [ ...{
-            [a++]: b,
-        } ] = [ "PASS" ];
-        console.log(b);
-    }
-    expect: {
-        var a = 0, b;
-        [ ...{
-            [a++]: b,
-        } ] = [ "PASS" ];
-        console.log(b);
-    }
-    expect_stdout: "PASS"
-    node_version: ">=6"
-}
-
 issue_4614: {
    options = {
        pure_getters: "strict",
@@ -1045,3 +1035,134 @@ issue_4614: {
    expect_stdout: true
    node_version: ">=6"
 }
+
+issue_4849: {
+    options = {
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        while (function() {
+            while (!console);
+        }(new function(a) {
+            console.log(typeof { ...a });
+        }(function() {})));
+    }
+    expect: {
+        while (function() {
+            while (!console);
+        }(function(a) {
+            console.log(typeof { ...function() {} });
+        }()));
+    }
+    expect_stdout: "object"
+    node_version: ">=8.3.0"
+}
+
+issue_4882_1: {
+    options = {
+        objects: true,
+        spreads: true,
+    }
+    input: {
+        var o = {
+            p: "PASS",
+            ... {
+                __proto__: {
+                    p: "FAIL 1",
+                    q: "FAIL 2",
+                },
+            },
+        };
+        console.log(o.p);
+        console.log(o.q);
+    }
+    expect: {
+        var o = {
+            p: "PASS",
+        };
+        console.log(o.p);
+        console.log(o.q);
+    }
+    expect_stdout: [
+        "PASS",
+        "undefined",
+    ]
+    node_version: ">=8.3.0"
+}
+
+issue_4882_2: {
+    options = {
+        objects: true,
+        spreads: true,
+    }
+    input: {
+        console.log(null == Object.getPrototypeOf({
+            ... {
+                __proto__: (console.log(42), null),
+            },
+        }) ? "FAIL" : "PASS");
+    }
+    expect: {
+        console.log(null == Object.getPrototypeOf({
+            ... {
+                __proto__: (console.log(42), null),
+            },
+        }) ? "FAIL" : "PASS");
+    }
+    expect_stdout: [
+        "42",
+        "PASS",
+    ]
+    node_version: ">=8.3.0"
+}
+
+issue_4882_3: {
+    options = {
+        objects: true,
+        spreads: true,
+    }
+    input: {
+        var o = {
+            __proto__: { p: 42 },
+            ... {
+                set __proto__(v) {},
+            },
+        };
+        console.log(o.__proto__ === Object.getPrototypeOf(o) ? "FAIL" : "PASS");
+        console.log(o.p);
+    }
+    expect: {
+        var o = {
+            __proto__: { p: 42 },
+            ["__proto__"]: void 0,
+        };
+        console.log(o.__proto__ === Object.getPrototypeOf(o) ? "FAIL" : "PASS");
+        console.log(o.p);
+    }
+    expect_stdout: [
+        "PASS",
+        "42",
+    ]
+    node_version: ">=8.3.0"
+}
+
+issue_5006: {
+    options = {
+        arguments: true,
+    }
+    input: {
+        console.log(function(b, c) {
+            c = "FAIL 2";
+            return arguments[1];
+        }(...[], "FAIL 1") || "PASS");
+    }
+    expect: {
+        console.log(function(b, c) {
+            c = "FAIL 2";
+            return arguments[1];
+        }(...[], "FAIL 1") || "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
--- a/test/compress/switches.js
+++ b/test/compress/switches.js
@@ -113,7 +113,7 @@ constant_switch_5: {
        // the break inside the if ruins our job
        // we can still get rid of irrelevant cases.
        switch (1) {
-          case 1:
+          default:
            x();
            if (foo) break;
            y();
@@ -300,6 +300,37 @@ drop_default_2: {
    }
 }

+drop_default_3: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        function f() {
+            console.log("PASS");
+            return 42;
+        }
+        switch (42) {
+          case f():
+            break;
+          case void console.log("FAIL"):
+          default:
+        }
+    }
+    expect: {
+        function f() {
+            console.log("PASS");
+            return 42;
+        }
+        switch (42) {
+          case f():
+          case void console.log("FAIL"):
+        }
+    }
+    expect_stdout: "PASS"
+}
+
 keep_default: {
    options = {
        dead_code: true,
@@ -423,7 +454,6 @@ drop_case_3: {
        switch ({}.p) {
          default:
          case void 0:
-            break;
          case c = "FAIL":
        }
        console.log(c);
@@ -454,7 +484,168 @@ drop_case_4: {
    expect_stdout: "PASS"
 }

-keep_case: {
+drop_case_5: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        switch (42) {
+          case void console.log("PASS 1"):
+            console.log("FAIL 1");
+          case 42:
+          case console.log("FAIL 2"):
+            console.log("PASS 2");
+        }
+    }
+    expect: {
+        switch (42) {
+          default:
+            void console.log("PASS 1");
+            console.log("PASS 2");
+        }
+    }
+    expect_stdout: [
+        "PASS 1",
+        "PASS 2",
+    ]
+}
+
+drop_case_6: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        switch (console.log("PASS 1"), 2) {
+          case 0:
+            console.log("FAIL 1");
+          case (console.log("PASS 2"), 1):
+            console.log("FAIL 2");
+        }
+    }
+    expect: {
+        switch (console.log("PASS 1"), 2) {
+          case (console.log("PASS 2"), 1):
+        }
+    }
+    expect_stdout: [
+        "PASS 1",
+        "PASS 2",
+    ]
+}
+
+drop_case_7: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        switch (2) {
+          case 0:
+            console.log("FAIL 1");
+          case (console.log("PASS 1"), 1):
+            console.log("FAIL 2");
+          case 2:
+            console.log("PASS 2");
+        }
+    }
+    expect: {
+        switch (2) {
+          default:
+            console.log("PASS 1"), 1;
+            console.log("PASS 2");
+        }
+    }
+    expect_stdout: [
+        "PASS 1",
+        "PASS 2",
+    ]
+}
+
+drop_case_8: {
+    options = {
+        dead_code: true,
+        switches: true,
+    }
+    input: {
+        function log(msg) {
+            console.log(msg);
+            return msg;
+        }
+        switch (log("foo")) {
+          case "bar":
+            log("moo");
+            break;
+          case log("baz"):
+            log("moo");
+            break;
+          default:
+            log("moo");
+        }
+    }
+    expect: {
+        function log(msg) {
+            console.log(msg);
+            return msg;
+        }
+        switch (log("foo")) {
+          case "bar":
+          case log("baz"):
+          default:
+            log("moo");
+        }
+    }
+    expect_stdout: [
+        "foo",
+        "baz",
+        "moo",
+    ]
+}
+
+drop_case_9: {
+    options = {
+        dead_code: true,
+        switches: true,
+    }
+    input: {
+        function log(msg) {
+            console.log(msg);
+            return msg;
+        }
+        switch (log("foo")) {
+          case log("bar"):
+            log("moo");
+            break;
+          case "baz":
+            log("moo");
+            break;
+          default:
+            log("moo");
+        }
+    }
+    expect: {
+        function log(msg) {
+            console.log(msg);
+            return msg;
+        }
+        switch (log("foo")) {
+          default:
+            log("bar");
+            log("moo");
+        }
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+        "moo",
+    ]
+}
+
+keep_case_1: {
    options = {
        dead_code: true,
        switches: true,
@@ -474,6 +665,76 @@ keep_case: {
    }
 }

+keep_case_2: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        switch ("foo") {
+          case console.log("bar"):
+          case console.log("baz"), "moo":
+        }
+    }
+    expect: {
+        switch ("foo") {
+          case console.log("bar"):
+          case console.log("baz"), "moo":
+        }
+    }
+    expect_stdout: [
+        "bar",
+        "baz",
+    ]
+}
+
+keep_case_3: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        var a;
+        switch (void console.log("PASS")) {
+          case a:
+          case console.log("FAIL"), 42:
+        }
+    }
+    expect: {
+        var a;
+        switch (void console.log("PASS")) {
+          case a:
+          case console.log("FAIL"), 42:
+        }
+    }
+    expect_stdout: "PASS"
+}
+
+keep_case_4: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        var a;
+        switch (void console.log("PASS")) {
+          case a:
+          case void console.log("FAIL"):
+        }
+    }
+    expect: {
+        var a;
+        switch (void console.log("PASS")) {
+          case a:
+          case void console.log("FAIL"):
+        }
+    }
+    expect_stdout: "PASS"
+}
+
 issue_376: {
    options = {
        dead_code: true,
@@ -661,7 +922,7 @@ issue_1680_1: {
          case f(0):
          case f(1):
            f(2);
-          case 2:
+          default:
            f(5);
        }
    }
@@ -924,7 +1185,6 @@ issue_2535: {
    }
    expect: {
        w(), 42;
-        42;
        y();
        z();
    }
@@ -950,7 +1210,6 @@ issue_1750: {
    expect: {
        var a = 0, b = 1;
        true;
-        a, true;
        b = 2;
        console.log(a, b);
    }
@@ -1088,7 +1347,8 @@ drop_switch_6: {
        }
    }
    expect: {
-        A === B;
+        A;
+        B;
        x();
        C !== D;
        y();
@@ -1181,3 +1441,170 @@ issue_4059: {
    }
    expect_stdout: "PASS"
 }
+
+issue_5008_1: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        reduce_vars: true,
+        switches: true,
+        unsafe: true,
+    }
+    input: {
+        console.log(function f() {
+            switch (f) {
+              case f:
+                return "PASS";
+              default:
+                return "FAIL";
+            }
+        }());
+    }
+    expect: {
+        console.log(function f() {
+            switch (f) {
+              default:
+                return "PASS";
+            }
+        }());
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5008_2: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        reduce_vars: true,
+        switches: true,
+        unsafe: true,
+    }
+    input: {
+        console.log(function(a) {
+            switch (a) {
+              case a:
+                return "PASS";
+              default:
+                return "FAIL";
+            }
+        }([]));
+    }
+    expect: {
+        console.log(function(a) {
+            switch (a) {
+              default:
+                return "PASS";
+            }
+        }([]));
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5008_3: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        reduce_vars: true,
+        switches: true,
+        unsafe: true,
+    }
+    input: {
+        console.log(function(a) {
+            switch (a) {
+              case a:
+                return "PASS";
+              default:
+                return "FAIL";
+            }
+        }({}));
+    }
+    expect: {
+        console.log(function(a) {
+            switch (a) {
+              default:
+                return "PASS";
+            }
+        }({}));
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5008_4: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        reduce_vars: true,
+        switches: true,
+    }
+    input: {
+        console.log(function(a) {
+            switch (a) {
+              case a:
+                return "PASS";
+              default:
+                return "FAIL";
+            }
+        }(/foo/));
+    }
+    expect: {
+        console.log(function(a) {
+            switch (a) {
+              default:
+                return "PASS";
+            }
+        }(/foo/));
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5010: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        var a;
+        switch (42) {
+          case console.log("PASS"):
+          case a:
+            console.log("FAIL");
+          case 42:
+        }
+    }
+    expect: {
+        var a;
+        switch (42) {
+          case console.log("PASS"):
+          case a:
+            console.log("FAIL");
+        }
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5012: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        switches: true,
+    }
+    input: {
+        switch (void 0) {
+          case console.log("PASS"):
+            break;
+          case void 0:
+          case 42:
+            console.log("FAIL");
+        }
+    }
+    expect: {
+        switch (void 0) {
+          case console.log("PASS"):
+            break;
+          default:
+            console.log("FAIL");
+        }
+    }
+    expect_stdout: "PASS"
+}
--- a/test/compress/templates.js
+++ b/test/compress/templates.js
@@ -62,6 +62,23 @@ tag_parentheses_arrow: {
    node_version: ">=4"
 }

+tag_parentheses_binary: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var f = function() {
+            console.log("PASS");
+        } || console
+        f``;
+    }
+    expect_exact: '(function(){console.log("PASS")}||console)``;'
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 tag_parentheses_new: {
    input: {
        (new function() {
@@ -87,6 +104,21 @@ tag_parentheses_sequence: {
    node_version: ">=4"
 }

+tag_parentheses_unary: {
+    input: {
+        var a;
+        try {
+            (~a)``;
+            (a++)``;
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_exact: 'var a;try{(~a)``;(a++)``}catch(e){console.log("PASS")}'
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 malformed_escape: {
    input: {
        (function(s) {
@@ -99,6 +131,105 @@ malformed_escape: {
    node_version: ">=4"
 }

+booleans: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        templates: true,
+    }
+    input: {
+        var a;
+        console.log(`$${a}${a}` ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a;
+        console.log("$" + a + a ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+escape_placeholder_1: {
+    options = {
+        templates: true,
+    }
+    input: {
+        console.log(`\${\n`);
+    }
+    expect: {
+        console.log(`\${
+`);
+    }
+    expect_stdout: [
+        "${",
+        "",
+    ]
+    node_version: ">=4"
+}
+
+escape_placeholder_2: {
+    options = {
+        evaluate: true,
+        templates: true,
+    }
+    input: {
+        console.log(`\n${"${"}\n`);
+    }
+    expect: {
+        console.log(`
+\${
+`);
+    }
+    expect_stdout: [
+        "",
+        "${",
+        "",
+    ]
+    node_version: ">=4"
+}
+
+escape_placeholder_3: {
+    options = {
+        evaluate: true,
+        templates: true,
+    }
+    input: {
+        console.log(`\n$${"{"}\n`);
+    }
+    expect: {
+        console.log(`
+\${
+`);
+    }
+    expect_stdout: [
+        "",
+        "${",
+        "",
+    ]
+    node_version: ">=4"
+}
+
+escape_placeholder_4: {
+    options = {
+        evaluate: true,
+        templates: true,
+    }
+    input: {
+        console.log(`\n${"$"}${"{"}\n`);
+    }
+    expect: {
+        console.log(`
+\${
+`);
+    }
+    expect_stdout: [
+        "",
+        "${",
+        "",
+    ]
+    node_version: ">=4"
+}
+
 evaluate: {
    options = {
        evaluate: true,
@@ -142,7 +273,7 @@ partial_evaluate: {
        console.log(`${6 * 7} foo ${console ? `PA` + "SS" : `FA` + `IL`}`);
    }
    expect: {
-        console.log(`42 foo ${console ? "PASS" : "FAIL"}`);
+        console.log("42 foo " + (console ? "PASS" : "FAIL"));
    }
    expect_stdout: "42 foo PASS"
    node_version: ">=4"
@@ -172,7 +303,7 @@ malformed_evaluate_2: {
        console.log(`\u0${0}b${5}`);
    }
    expect: {
-        console.log(`\u0${0}b5`);
+        console.log(`\u00b` + 5);
    }
    expect_stdout: true
    node_version: ">=4"
@@ -206,7 +337,7 @@ malformed_evaluate_4: {
        console.log("\\u00b5");
    }
    expect_stdout: "\\u00b5"
-    node_version: ">=8"
+    node_version: ">=8.10.0"
 }

 unsafe_evaluate: {
@@ -222,7 +353,7 @@ unsafe_evaluate: {
        console.log("\\uFo");
    }
    expect_stdout: "\\uFo"
-    node_version: ">=8"
+    node_version: ">=8.10.0"
 }

 side_effects_1: {
@@ -283,6 +414,21 @@ unsafe_side_effects: {
    node_version: ">=4"
 }

+pure_funcs: {
+    options = {
+        pure_funcs: "Math.random",
+        side_effects: true,
+    }
+    input: {
+        Math.random`${console.log("PASS")}`;
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 issue_4604: {
    options = {
        collapse_vars: true,
@@ -310,13 +456,14 @@ issue_4604: {
 issue_4606: {
    options = {
        evaluate: true,
+        strings: true,
        templates: true,
    }
    input: {
        console.log(`${typeof A} ${"\r"} ${"\\"} ${"`"}`);
    }
    expect: {
-        console.log(`${typeof A} \r \\ \``);
+        console.log(typeof A + " \r \\ `");
    }
    expect_stdout: "undefined \r \\ `"
    node_version: ">=4"
@@ -343,7 +490,7 @@ issue_4676: {
        reduce_vars: true,
        templates: true,
        toplevel: true,
-        unsafe:true,
+        unsafe: true,
        unused: true,
    }
    input: {
@@ -366,3 +513,259 @@ issue_4676: {
    expect_stdout: "PASS"
    node_version: ">=4"
 }
+
+issue_4931: {
+    options = {
+        evaluate: true,
+        templates: true,
+        unsafe: true,
+    }
+    input: {
+        console.log(String.raw`${typeof A} ${"\r"}`);
+        console.log(String.raw`${"\\"} ${"`"}`);
+    }
+    expect: {
+        console.log(String.raw`${typeof A} ${"\r"}`);
+        console.log("\\ `");
+    }
+    expect_stdout: [
+        "undefined \r",
+        "\\ `",
+    ]
+    node_version: ">=4"
+}
+
+issue_5125_1: {
+    options = {
+        evaluate: true,
+        strings: true,
+        templates: true,
+    }
+    input: {
+        console.log(`PASS ${typeof A}`);
+    }
+    expect: {
+        console.log("PASS " + typeof A);
+    }
+    expect_stdout: "PASS undefined"
+    node_version: ">=4"
+}
+
+issue_5125_2: {
+    options = {
+        evaluate: true,
+        strings: true,
+        templates: true,
+    }
+    input: {
+        console.log(`PASS
+${typeof A}`);
+    }
+    expect: {
+        console.log(`PASS
+` + typeof A);
+    }
+    expect_stdout: [
+        "PASS",
+        "undefined",
+    ]
+    node_version: ">=4"
+}
+
+issue_5125_3: {
+    options = {
+        evaluate: true,
+        strings: true,
+        templates: true,
+    }
+    input: {
+        console.log(`PASS\n${typeof A}`);
+    }
+    expect: {
+        console.log(`PASS
+` + typeof A);
+    }
+    expect_stdout: [
+        "PASS",
+        "undefined",
+    ]
+    node_version: ">=4"
+}
+
+issue_5125_4: {
+    options = {
+        evaluate: true,
+        strings: true,
+        templates: true,
+    }
+    input: {
+        console.log(`PASS
+
+${typeof A}`);
+    }
+    expect: {
+        console.log(`PASS
+
+` + typeof A);
+    }
+    expect_stdout: [
+        "PASS",
+        "",
+        "undefined",
+    ]
+    node_version: ">=4"
+}
+
+issue_5125_5: {
+    options = {
+        evaluate: true,
+        strings: true,
+        templates: true,
+    }
+    input: {
+        console.log(`PASS\n\n${typeof A}`);
+    }
+    expect: {
+        console.log(`PASS
+
+` + typeof A);
+    }
+    expect_stdout: [
+        "PASS",
+        "",
+        "undefined",
+    ]
+    node_version: ">=4"
+}
+
+issue_5125_6: {
+    options = {
+        evaluate: true,
+        strings: true,
+        templates: true,
+    }
+    input: {
+        console.log(`${typeof A} ${typeof B} PASS`);
+    }
+    expect: {
+        console.log(typeof A + ` ${typeof B} PASS`);
+    }
+    expect_stdout: "undefined undefined PASS"
+    node_version: ">=4"
+}
+
+issue_5125_7: {
+    options = {
+        evaluate: true,
+        strings: true,
+        templates: true,
+    }
+    input: {
+        console.log(`${typeof A} ${typeof B} ${typeof C} PASS`);
+    }
+    expect: {
+        console.log(typeof A + ` ${typeof B} ${typeof C} PASS`);
+    }
+    expect_stdout: "undefined undefined undefined PASS"
+    node_version: ">=4"
+}
+
+issue_5125_8: {
+    options = {
+        evaluate: true,
+        strings: true,
+        templates: true,
+    }
+    input: {
+        console.log(`${typeof A}${typeof B}${typeof C} PASS`);
+    }
+    expect: {
+        console.log(typeof A + typeof B + typeof C + " PASS");
+    }
+    expect_stdout: "undefinedundefinedundefined PASS"
+    node_version: ">=4"
+}
+
+issue_5136: {
+    options = {
+        templates: true,
+    }
+    input: {
+        console.log(`${A = []}${A[0] = 42}`);
+    }
+    expect: {
+        console.log(`` + (A = []) + (A[0] = 42));
+    }
+    expect_stdout: "42"
+    node_version: ">=4"
+}
+
+issue_5145_1: {
+    options = {
+        strings: true,
+        templates: true,
+    }
+    input: {
+        var a = [];
+        console.log(`${a}${a[0] = 42}
+`);
+    }
+    expect: {
+        var a = [];
+        console.log(`${a}${a[0] = 42}
+`);
+    }
+    expect_stdout: [
+        "42",
+        "",
+    ]
+    node_version: ">=4"
+}
+
+issue_5145_2: {
+    options = {
+        strings: true,
+        templates: true,
+    }
+    input: {
+        var a = [];
+        console.log(`${a}${a}${a[0] = 42}
+`);
+    }
+    expect: {
+        var a = [];
+        console.log("" + a + a + (a[0] = 42) + `
+`);
+    }
+    expect_stdout: [
+        "42",
+        "",
+    ]
+    node_version: ">=4"
+}
+
+issue_5199: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = function() {
+            console.log(typeof b);
+        }``;
+        {
+            const b = a;
+        }
+    }
+    expect: {
+        var a = function() {
+            console.log(typeof b);
+        }``;
+        {
+            const b = a;
+        }
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}
--- a/test/compress/transform.js
+++ b/test/compress/transform.js
@@ -95,7 +95,7 @@ while_if_break: {
        }
    }
    expect: {
-        for(; a && (b && c && d, !e););
+        for (; a && (b && c && d, !e););
    }
 }

--- a/test/compress/typeof.js
+++ b/test/compress/typeof.js
@@ -436,6 +436,245 @@ emberjs_global: {
    expect_stdout: Error("PASS")
 }

+reassign: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A = void 0;
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A = void 0;
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect_stdout: "PASS"
+}
+
+reassign_call: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        function f() {
+            A = void 0;
+        }
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            f();
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect: {
+        A = console;
+        function f() {
+            A = void 0;
+        }
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            f();
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect_stdout: "PASS"
+}
+
+reassign_conditional: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A &&= void 0;
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A &&= void 0;
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+reassign_do: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        if_return: true,
+        passes: 2,
+        reduce_vars: true,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        (function() {
+            if ("undefined" == typeof A)
+                return;
+            var a = A, i = 2;
+            do {
+                console.log(void 0 === A, void 0 === a);
+                A = void 0;
+            } while (--i);
+        })();
+    }
+    expect: {
+        A = console;
+        (function() {
+            if ("undefined" != typeof A) {
+                var a = A, i = 2;
+                do {
+                    console.log(void 0 === A, (a, false));
+                    A = void 0;
+                } while (--i);
+            }
+        })();
+    }
+    expect_stdout: [
+        "false false",
+        "true false",
+    ]
+}
+
+reassign_for: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        reduce_vars: true,
+        toplevel: true,
+        typeofs: true,
+    }
+    input: {
+        if (A = console, "undefined" != typeof A)
+            for (var a = A, i = 0; i < 2; i++)
+                console.log(void 0 === A, void 0 === a),
+                A = void 0;
+    }
+    expect: {
+        if (A = console, "undefined" != typeof A)
+            for (var a = A, i = 0; i < 2; i++)
+                console.log(void 0 === A, (a, false)),
+                A = void 0;
+    }
+    expect_stdout: [
+        "false false",
+        "true false",
+    ]
+}
+
+reassign_for_in: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        reduce_vars: true,
+        typeofs: true,
+    }
+    input: {
+        (A = console) && "undefined" != typeof A && function(a) {
+            for (var k in [ a = A, 42 ]) {
+                console.log(void 0 === A, void 0 === a);
+                A = void 0;
+            }
+        }();
+    }
+    expect: {
+        (A = console) && "undefined" != typeof A && function(a) {
+            for (var k in [ a = A, 42 ]) {
+                console.log(void 0 === A, (a, false));
+                A = void 0;
+            }
+        }();
+    }
+    expect_stdout: [
+        "false false",
+        "true false",
+    ]
+}
+
+reassign_iife: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else (function() {
+            A = void 0;
+        })(console.log(void 0 === A ? "FAIL 2" : "PASS"));
+    }
+    expect: {
+        A = console;
+        "undefined" == typeof A ? console.log("FAIL 1") : function() {
+            A = void 0;
+        }(console.log((A, false) ? "FAIL 2" : "PASS"));
+    }
+    expect_stdout: "PASS"
+}
+
+reassign_property: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A.p = void 0;
+            console.log(void 0 === A ? "FAIL 2" : "PASS");
+        }
+    }
+    expect: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A.p = void 0;
+            console.log((A, false) ? "FAIL 2" : "PASS");
+        }
+    }
+    expect_stdout: "PASS"
+}
+
 issue_3817: {
    options = {
        comparisons: true,
--- a/test/compress/unicode.js
+++ b/test/compress/unicode.js
@@ -67,7 +67,8 @@ unicode_escaped_identifier_2: {
    }
    expect_exact: 'var a="foo";var \u{10000}="bar";console.log(a,\u{10000});'
    expect_stdout: "foo bar"
-    node_version: ">=4"
+    // non-BMP support is platform-dependent on Node.js v4
+    node_version: ">=6"
 }

 unicode_identifier_ascii_only: {
@@ -200,7 +201,8 @@ surrogate_pair: {
    }
    expect_exact: 'var \ud87e\udc00={"\ud87e\udc01":"\udbc0\udc00"};\ud87e\udc00.\ud87e\udc02="\udbc0\udc01";console.log(typeof \ud87e\udc00,\ud87e\udc00.\ud87e\udc01,\ud87e\udc00["\ud87e\udc02"]);'
    expect_stdout: "object \udbc0\udc00 \udbc0\udc01"
-    node_version: ">=4"
+    // non-BMP support is platform-dependent on Node.js v4
+    node_version: ">=6"
 }

 surrogate_pair_ascii: {
@@ -216,5 +218,6 @@ surrogate_pair_ascii: {
    }
    expect_exact: 'var \\u{2f800}={"\\ud87e\\udc01":"\\udbc0\\udc00"};\\u{2f800}.\\u{2f802}="\\udbc0\\udc01";console.log(typeof \\u{2f800},\\u{2f800}.\\u{2f801},\\u{2f800}["\\ud87e\\udc02"]);'
    expect_stdout: "object \udbc0\udc00 \udbc0\udc01"
-    node_version: ">=4"
+    // non-BMP support is platform-dependent on Node.js v4
+    node_version: ">=6"
 }
--- a/test/compress/varify.js
+++ b/test/compress/varify.js
@@ -13,10 +13,10 @@ reduce_merge_const: {
        console.log(b);
    }
    expect: {
-        var b = console;
-        console.log(typeof b);
-        b = typeof b;
-        console.log(b);
+        var a = console;
+        console.log(typeof a);
+        a = typeof a;
+        console.log(a);
    }
    expect_stdout: [
        "object",
@@ -41,10 +41,10 @@ reduce_merge_let: {
    }
    expect: {
        "use strict";
-        var b = console;
-        console.log(typeof b);
-        b = typeof b;
-        console.log(b);
+        var a = console;
+        console.log(typeof a);
+        a = typeof a;
+        console.log(a);
    }
    expect_stdout: [
        "object",
@@ -111,7 +111,7 @@ hoist_props_const: {
        }
    }
    expect: {
-        var o_p = "PASS";
+        var o = 0, o_p = "PASS";
        console.log(o_p);
    }
    expect_stdout: "PASS"
@@ -136,7 +136,7 @@ hoist_props_let: {
    }
    expect: {
        "use strict";
-        var o_p = "PASS";
+        var o, o_p = "PASS";
        console.log(o_p);
    }
    expect_stdout: "PASS"
@@ -523,3 +523,93 @@ default_init: {
    expect_stdout: "PASS"
    node_version: ">=4"
 }
+
+issue_4933_1: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+        varify: true,
+    }
+    input: {
+        console.log(f());
+        function f() {
+            var a;
+            for (console in a = [ f ]) {
+                const b = a;
+            }
+        }
+    }
+    expect: {
+        console.log(function f() {
+            var a;
+            for (console in a = [ f ]) {
+                const b = a;
+            }
+        }());
+    }
+    expect_stdout: "undefined"
+}
+
+issue_4933_2: {
+    options = {
+        passes: 2,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+        varify: true,
+    }
+    input: {
+        console.log(f());
+        function f() {
+            var a;
+            for (console in a = [ f ]) {
+                const b = a;
+            }
+        }
+    }
+    expect: {
+        console.log(function f() {
+            for (console in [ f ]);
+        }());
+    }
+    expect_stdout: "undefined"
+}
+
+issue_4954: {
+    options = {
+        functions: true,
+        reduce_vars: true,
+        unused: true,
+        varify: true,
+    }
+    input: {
+        "use strict";
+        (function() {
+            {
+                let a = console;
+                console.log(typeof a);
+            }
+            {
+                let a = function() {};
+                a && console.log(typeof a);
+            }
+        })();
+    }
+    expect: {
+        "use strict";
+        (function() {
+            var a = console;
+            console.log(typeof a);
+            {
+                let a = function() {};
+                a && console.log(typeof a);
+            }
+        })();
+    }
+    expect_stdout: [
+        "object",
+        "function",
+    ]
+    node_version: ">=4"
+}
--- a/test/compress/webkit.js
+++ b/test/compress/webkit.js
@@ -61,7 +61,7 @@ lambda_name_mangle: {

 lambda_name_mangle_ie8: {
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
@@ -95,7 +95,7 @@ function_name_mangle_ie8: {
        unused: true,
    }
    mangle = {
-        ie8: true,
+        ie: true,
        toplevel: true,
    }
    input: {
--- a/test/compress/yields.js
+++ b/test/compress/yields.js
@@ -96,7 +96,7 @@ pause_resume: {
    node_version: ">=4"
 }

-arrow_yield: {
+arrow_yield_1: {
    input: {
        yield = "PASS";
        console.log(function*() {
@@ -108,6 +108,18 @@ arrow_yield: {
    node_version: ">=4"
 }

+arrow_yield_2: {
+    input: {
+        console.log(typeof function *() {
+            // Syntax error on Node.js v6+
+            return (yield) => {};
+        }().next().value);
+    }
+    expect_exact: "console.log(typeof function*(){return(yield)=>{}}().next().value);"
+    expect_stdout: "function"
+    node_version: "4"
+}
+
 for_of: {
    input: {
        function* f() {
@@ -150,6 +162,27 @@ for_await_of: {
    node_version: ">=10"
 }

+comment_newline: {
+    beautify = {
+        comments: "all",
+    }
+    input: {
+        console.log(function*() {
+            yield (
+                /* */
+                "PASS"
+            );
+        }().next().value);
+    }
+    expect_exact: [
+        "console.log(function*(){",
+        "/* */",
+        'yield"PASS"}().next().value);',
+    ]
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 collapse_vars_1: {
    options = {
        collapse_vars: true,
@@ -716,7 +749,7 @@ lift_sequence: {
    node_version: ">=4"
 }

-inline_nested_yield: {
+inline_nested: {
    options = {
        inline: true,
        sequences: true,
@@ -751,6 +784,118 @@ inline_nested_yield: {
    node_version: ">=4"
 }

+inline_nested_async: {
+    options = {
+        awaits: true,
+        inline: true,
+        sequences: true,
+        side_effects: true,
+        yields: true,
+    }
+    input: {
+        console.log("foo");
+        var a = async function*() {
+            console.log(await(yield* async function*() {
+                yield {
+                    then: r => r("bar"),
+                };
+                return "baz";
+            }()));
+        }();
+        console.log("moo");
+        a.next().then(function f(b) {
+            console.log(b.value);
+            b.done || a.next().then(f);
+        });
+        console.log("moz");
+    }
+    expect: {
+        console.log("foo");
+        var a = async function*() {
+            console.log((yield {
+                then: r => r("bar"),
+            }, await "baz"));
+        }();
+        console.log("moo"),
+        a.next().then(function f(b) {
+            console.log(b.value),
+            b.done || a.next().then(f);
+        }),
+        console.log("moz");
+    }
+    expect_stdout: [
+        "foo",
+        "moo",
+        "moz",
+        "bar",
+        "baz",
+        "undefined",
+    ]
+    node_version: ">=10"
+}
+
+inline_nested_block: {
+    options = {
+        if_return: true,
+        inline: true,
+        yields: true,
+    }
+    input: {
+        var a = function*() {
+            yield* function*() {
+                for (var a of [ "foo", "bar" ])
+                    yield a;
+                return "FAIL";
+            }();
+        }(), b;
+        do {
+            b = a.next();
+            console.log(b.value);
+        } while (!b.done);
+    }
+    expect: {
+        var a = function*() {
+            for (var a of [ "foo", "bar" ])
+                yield a;
+            "FAIL";
+        }(), b;
+        do {
+            b = a.next();
+            console.log(b.value);
+        } while (!b.done);
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+        "undefined",
+    ]
+    node_version: ">=4"
+}
+
+dont_inline_nested: {
+    options = {
+        inline: true,
+    }
+    input: {
+        var yield = "PASS";
+        (function*() {
+            (function() {
+                console.log(yield);
+            })();
+        })().next();
+    }
+    expect: {
+        var yield = "PASS";
+        (function*() {
+            (function() {
+                console.log(yield);
+            })();
+        })().next();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 drop_body: {
    options = {
        side_effects: true,
@@ -831,10 +976,10 @@ issue_4454_2: {
        f("PASS");
    }
    expect: {
-        function f(b) {
-            (function*(c = console.log(b)) {})();
-            var b = 42..toString();
-            console.log(b);
+        function f(a) {
+            (function*(c = console.log(a)) {})();
+            var a = 42..toString();
+            console.log(a);
        }
        f("PASS");
    }
@@ -937,7 +1082,7 @@ issue_4639_1: {
        }().next().value());
    }
    expect_stdout: "PASS"
-    node_version: ">=4"
+    node_version: ">=4 <7 || >=8.7.0"
 }

 issue_4639_2: {
@@ -1062,3 +1207,245 @@ issue_4769_2: {
    expect_stdout: "PASS"
    node_version: ">=6"
 }
+
+issue_5019_1: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        (function(a) {
+            return a = function*() {
+                console.log(typeof a);
+            }();
+        })().next();
+    }
+    expect: {
+        (function(a) {
+            return a = function*() {
+                console.log(typeof a);
+            }();
+        })().next();
+    }
+    expect_stdout: "object"
+    node_version: ">=4"
+}
+
+issue_5019_2: {
+    options = {
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        var a = [];
+        for (var b in "foo")
+            a.push(function(c) {
+                return function*() {
+                    console.log(c);
+                }();
+            }(b));
+        a.map(function(d) {
+            return d.next();
+        });
+    }
+    expect: {
+        var a = [];
+        for (var b in "foo")
+            a.push(function(c) {
+                return function*() {
+                    console.log(c);
+                }();
+            }(b));
+        a.map(function(d) {
+            return d.next();
+        });
+    }
+    expect_stdout: [
+        "0",
+        "1",
+        "2",
+    ]
+    node_version: ">=4"
+}
+
+issue_5032_normal: {
+    options = {
+        merge_vars: true,
+        webkit: false,
+    }
+    input: {
+        function log(value) {
+            console.log(value);
+            return value;
+        }
+        function *f(a) {
+            var b = log(a), c = b;
+            log(b);
+            log(c);
+        }
+        f("PASS").next();
+    }
+    expect: {
+        function log(value) {
+            console.log(value);
+            return value;
+        }
+        function *f(a) {
+            var a = log(a), c = a;
+            log(a);
+            log(c);
+        }
+        f("PASS").next();
+    }
+    expect_stdout: [
+        "PASS",
+        "PASS",
+        "PASS",
+    ]
+    node_version: ">=4"
+}
+
+issue_5032_webkit: {
+    options = {
+        merge_vars: true,
+        webkit: true,
+    }
+    input: {
+        function log(value) {
+            console.log(value);
+            return value;
+        }
+        function *f(a) {
+            var b = log(a), c = b;
+            log(b);
+            log(c);
+        }
+        f("PASS").next();
+    }
+    expect: {
+        function log(value) {
+            console.log(value);
+            return value;
+        }
+        function *f(a) {
+            var b = log(a), c = b;
+            log(b);
+            log(c);
+        }
+        f("PASS").next();
+    }
+    expect_stdout: [
+        "PASS",
+        "PASS",
+        "PASS",
+    ]
+    node_version: ">=4"
+}
+
+issue_5034: {
+    options = {
+        functions: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var yield = function f() {
+                return function*() {
+                    return f;
+                };
+            };
+            return yield()().next().value === yield;
+        }() ? "PASS" : "FAIL");
+    }
+    expect: {
+        console.log(function() {
+            var yield = function f() {
+                return function*() {
+                    return f;
+                };
+            };
+            return yield()().next().value === yield;
+        }() ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_5076_1: {
+    options = {
+        evaluate: true,
+        hoist_vars: true,
+        pure_getters: "strict",
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+        yields: true,
+    }
+    input: {
+        var a;
+        console.log("PASS");
+        var b = function*({
+            p: {},
+        }) {}({
+            p: { a } = 42,
+        });
+    }
+    expect: {
+        var a;
+        console.log("PASS"),
+        a = 42["a"];
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5076_2: {
+    options = {
+        evaluate: true,
+        hoist_vars: true,
+        passes: 2,
+        pure_getters: "strict",
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+        yields: true,
+    }
+    input: {
+        var a;
+        console.log("PASS");
+        var b = function*({
+            p: {},
+        }) {}({
+            p: { a } = 42,
+        });
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5177: {
+    options = {
+        properties: true,
+    }
+    input: {
+        console.log(typeof function*() {
+            return {
+                p(yield) {},
+            }.p;
+        }().next().value);
+    }
+    expect: {
+        console.log(typeof function*() {
+            return {
+                p(yield) {},
+            }.p;
+        }().next().value);
+    }
+    expect_stdout: "function"
+    node_version: ">=4"
+}
--- a/test/input/invalid/assign_4.js
+++ b/test/input/invalid/assign_4.js
@@ -1 +1 @@
-++null
+console.log(4 || (null = 4));
--- a/test/input/invalid/assign_5.js
+++ b/test/input/invalid/assign_5.js
@@ -0,0 +1 @@
+console.log(5 || ([]?.length ^= 5));
--- a/test/input/invalid/for-await.js
+++ b/test/input/invalid/for-await.js
@@ -0,0 +1 @@
+for await (; console.log(42););
--- a/test/input/invalid/optional-template.js
+++ b/test/input/invalid/optional-template.js
@@ -0,0 +1 @@
+console?.log``;
--- a/test/input/reduce/diff_error.reduced.js
+++ b/test/input/reduce/diff_error.reduced.js
@@ -1,7 +1,5 @@
 // (beautified)
-console.log(function() {
-    return 1 + .1 + .1;
-}());
+console.log(1 + .1 + .1);
 // output: 1.2000000000000002
 // 
 // minify: 1.2
--- a/test/jetstream.js
+++ b/test/jetstream.js
@@ -58,22 +58,31 @@ if (typeof phantom == "undefined") {
    }).listen();
    server.on("listening", function() {
        var port = server.address().port;
-        if (debug) {
-            console.log("http://localhost:" + port + "/");
-        } else (function install() {
-            child_process.spawn(process.platform == "win32" ? "npm.cmd" : "npm", [
+        if (debug) return console.log("http://localhost:" + port + "/");
+        var cmd = process.platform == "win32" ? "npm.cmd" : "npm";
+
+        function npm(args, done) {
+            child_process.spawn(cmd, args, { stdio: [ "ignore", 1, 2 ] }).on("exit", done);
+        }
+
+        (function install() {
+            npm([
                "install",
+                "graceful-fs@4.2.6",
+                "is-my-json-valid@2.20.5",
                "phantomjs-prebuilt@2.1.14",
                "--no-audit",
                "--no-optional",
                "--no-save",
                "--no-update-notifier",
-            ], {
-                stdio: [ "ignore", 1, 2 ]
-            }).on("exit", function(code) {
+            ], function(code) {
                if (code) {
                    console.log("npm install failed with code", code);
-                    return install();
+                    return npm([
+                        "cache",
+                        "clean",
+                        "--force",
+                    ], install);
                }
                var program = require("phantomjs-prebuilt").exec(process.argv[1], port);
                program.stdout.pipe(process.stdout);
--- a/test/mocha/cli.js
+++ b/test/mocha/cli.js
@@ -2,6 +2,7 @@ var assert = require("assert");
 var exec = require("child_process").exec;
 var fs = require("fs");
 var run_code = require("../sandbox").run_code;
+var semver = require("semver");
 var to_ascii = require("../node").to_ascii;

 function read(path) {
@@ -12,10 +13,13 @@ describe("bin/uglifyjs", function() {
    var uglifyjscmd = '"' + process.argv[0] + '" bin/uglifyjs';
    it("Should produce a functional build when using --self", function(done) {
        this.timeout(30000);
-        var command = uglifyjscmd + ' --self -cm --wrap WrappedUglifyJS';
-        exec(command, {
-            maxBuffer: 1048576
-        }, function(err, stdout) {
+        var command = [
+            uglifyjscmd,
+            "--self",
+            semver.satisfies(process.version, "<=0.12") ? "-mc hoist_funs" : "-mc",
+            "--wrap WrappedUglifyJS",
+        ].join(" ");
+        exec(command, { maxBuffer: 1048576 }, function(err, stdout) {
            if (err) throw err;
            eval(stdout);
            assert.strictEqual(typeof WrappedUglifyJS, "object");
@@ -184,6 +188,30 @@ describe("bin/uglifyjs", function() {
            child.stdin.end(read("test/input/issue-3040/input.js"));
        }, 1000);
    });
+    it("Should work with --keep-fargs (mangle only)", function(done) {
+        var command = uglifyjscmd + ' test/input/issue-1431/sample.js --keep-fargs -m';
+        exec(command, function(err, stdout) {
+            if (err) throw err;
+            assert.strictEqual(stdout, "function f(x){return function(){function n(a){return a*a}return x(n)}}function g(op){return op(1)+op(2)}console.log(f(g)()==5);\n");
+            done();
+        });
+    });
+    it("Should work with --keep-fargs (mangle & compress)", function(done) {
+        var command = uglifyjscmd + ' test/input/issue-1431/sample.js --keep-fargs -m -c';
+        exec(command, function(err, stdout) {
+            if (err) throw err;
+            assert.strictEqual(stdout, "function f(x){return function(){return x(function(a){return a*a})}}function g(op){return op(1)+op(2)}console.log(5==f(g)());\n");
+            done();
+        });
+    });
+    it("Should work with keep_fargs under mangler options", function(done) {
+        var command = uglifyjscmd + ' test/input/issue-1431/sample.js -m keep_fargs=true';
+        exec(command, function(err, stdout) {
+            if (err) throw err;
+            assert.strictEqual(stdout, "function f(x){return function(){function n(a){return a*a}return x(n)}}function g(op){return op(1)+op(2)}console.log(f(g)()==5);\n");
+            done();
+        });
+    });
    it("Should work with --keep-fnames (mangle only)", function(done) {
        var command = uglifyjscmd + ' test/input/issue-1431/sample.js --keep-fnames -m';
        exec(command, function(err, stdout) {
@@ -193,10 +221,10 @@ describe("bin/uglifyjs", function() {
        });
    });
    it("Should work with --keep-fnames (mangle & compress)", function(done) {
-        var command = uglifyjscmd + ' test/input/issue-1431/sample.js --keep-fnames -m -c unused=false';
+        var command = uglifyjscmd + ' test/input/issue-1431/sample.js --keep-fnames -m -c';
        exec(command, function(err, stdout) {
            if (err) throw err;
-            assert.strictEqual(stdout, "function f(r){return function(){function n(n){return n*n}return r(n)}}function g(n){return n(1)+n(2)}console.log(5==f(g)());\n");
+            assert.strictEqual(stdout, "function f(n){return function(){return n(function n(r){return r*r})}}function g(n){return n(1)+n(2)}console.log(5==f(g)());\n");
            done();
        });
    });
@@ -427,16 +455,30 @@ describe("bin/uglifyjs", function() {
            done();
        });
    });
-    it("Should throw syntax error (++null)", function(done) {
+    it("Should throw syntax error (null = 4)", function(done) {
        var command = uglifyjscmd + " test/input/invalid/assign_4.js";
        exec(command, function(err, stdout, stderr) {
            assert.ok(err);
            assert.strictEqual(stdout, "");
            assert.strictEqual(stderr.split(/\n/).slice(0, 4).join("\n"), [
-                "Parse error at test/input/invalid/assign_4.js:1,0",
-                "++null",
-                "^",
-                "ERROR: Invalid use of ++ operator",
+                "Parse error at test/input/invalid/assign_4.js:1,23",
+                "console.log(4 || (null = 4));",
+                "                       ^",
+                "ERROR: Invalid assignment",
+            ].join("\n"));
+            done();
+        });
+    });
+    it("Should throw syntax error ([]?.length ^= 5)", function(done) {
+        var command = uglifyjscmd + " test/input/invalid/assign_5.js";
+        exec(command, function(err, stdout, stderr) {
+            assert.ok(err);
+            assert.strictEqual(stdout, "");
+            assert.strictEqual(stderr.split(/\n/).slice(0, 4).join("\n"), [
+                "Parse error at test/input/invalid/assign_5.js:1,29",
+                "console.log(5 || ([]?.length ^= 5));",
+                "                             ^",
+                "ERROR: Invalid assignment",
            ].join("\n"));
            done();
        });
@@ -679,6 +721,20 @@ describe("bin/uglifyjs", function() {
            done();
        });
    });
+    it("Should throw syntax error (for-await)", function(done) {
+        var command = uglifyjscmd + " test/input/invalid/for-await.js";
+        exec(command, function(err, stdout, stderr) {
+            assert.ok(err);
+            assert.strictEqual(stdout, "");
+            assert.strictEqual(stderr.split(/\n/).slice(0, 4).join("\n"), [
+                "Parse error at test/input/invalid/for-await.js:1,11",
+                "for await (; console.log(42););",
+                "           ^",
+                "ERROR: Unexpected token: punc «;»",
+            ].join("\n"));
+            done();
+        });
+    });
    it("Should throw syntax error (switch defaults)", function(done) {
        var command = uglifyjscmd + " test/input/invalid/switch.js";
        exec(command, function(err, stdout, stderr) {
@@ -693,6 +749,20 @@ describe("bin/uglifyjs", function() {
            done();
        });
    });
+    it("Should throw syntax error (console?.log``)", function(done) {
+        var command = uglifyjscmd + " test/input/invalid/optional-template.js";
+        exec(command, function(err, stdout, stderr) {
+            assert.ok(err);
+            assert.strictEqual(stdout, "");
+            assert.strictEqual(stderr.split(/\n/).slice(0, 4).join("\n"), [
+                "Parse error at test/input/invalid/optional-template.js:1,12",
+                "console?.log``;",
+                "            ^",
+                "ERROR: Invalid template on optional chain",
+            ].join("\n"));
+            done();
+        });
+    });
    it("Should handle literal string as source map input", function(done) {
        var command = [
            uglifyjscmd,
--- a/test/mocha/comments.js
+++ b/test/mocha/comments.js
@@ -191,7 +191,7 @@ describe("comments", function() {
    });

    it("Should correctly preserve new lines around comments", function() {
-        var tests = [
+        [
            [
                "// foo",
                "// bar",
--- a/test/mocha/glob.js
+++ b/test/mocha/glob.js
@@ -1,7 +1,6 @@
 var assert = require("assert");
 var exec = require("child_process").exec;
 var path = require("path");
-var readFileSync = require("fs").readFileSync;

 describe("bin/uglifyjs with input file globs", function() {
    var uglifyjscmd = '"' + process.argv[0] + '" bin/uglifyjs';
--- a/test/mocha/ie8.js
+++ b/test/mocha/ie8.js
@@ -1,21 +0,0 @@
-var assert = require("assert");
-var UglifyJS = require("../..");
-
-describe("ie8", function() {
-    it("Should be able to minify() with undefined as catch parameter in a try...catch statement", function() {
-        assert.strictEqual(
-            UglifyJS.minify([
-                "function a(b){",
-                "    try {",
-                "        throw 'Stuff';",
-                "    } catch (undefined) {",
-                "        console.log('caught: ' + undefined);",
-                "    }",
-                "    console.log('undefined is ' + undefined);",
-                "    return b === undefined;",
-                "};",
-            ].join("\n")).code,
-            'function a(o){try{throw"Stuff"}catch(o){console.log("caught: "+o)}return console.log("undefined is "+void 0),void 0===o}'
-        );
-    });
-});
--- a/test/mocha/let.js
+++ b/test/mocha/let.js
@@ -1,5 +1,5 @@
 var assert = require("assert");
-var UglifyJS = require("../..");
+var UglifyJS = require("../node");

 describe("let", function() {
    this.timeout(30000);
@@ -7,11 +7,11 @@ describe("let", function() {
        // Produce a lot of variables in a function and run it through mangle.
        var s = '"dddddeeeeelllllooooottttt"; function foo() {';
        for (var i = 0; i < 18000; i++) {
-            s += "var v" + i + "=0;";
+            s += "var v" + i + "=[];";
        }
        s += '}';
        var result = UglifyJS.minify(s, {
-            compress: false
+            compress: false,
        }).code;

        // Verify that select keywords and reserved keywords not produced
@@ -41,7 +41,7 @@ describe("let", function() {
        }
        var result = UglifyJS.minify(s, {
            compress: false,
-            ie8: true,
+            ie: true,
            mangle: {
                properties: true,
            }
@@ -54,4 +54,43 @@ describe("let", function() {
            assert.notStrictEqual(result.indexOf('v["' + name + '"]'), -1);
        });
    });
+    it("Should parse `let` as name correctly", function() {
+        [
+            "for(var let;let;let)let;",
+            "function let(let){let}",
+        ].forEach(function(code) {
+            var ast = UglifyJS.parse(code);
+            assert.strictEqual(ast.print_to_string(), code);
+            assert.throws(function() {
+                UglifyJS.parse('"use strict";' + code);
+            }, function(e) {
+                return e instanceof UglifyJS.JS_Parse_Error && e.message == "Unexpected let in strict mode";
+            }, code);
+        });
+    });
+    it("Should throw on ambiguous use of `let`", function() {
+        [
+            "export let",
+            [
+                "let",
+                "console.log(42)",
+            ].join("\n"),
+            [
+                "let",
+                "[ console.log(42) ]",
+            ].join("\n"),
+            [
+                "let",
+                "{",
+                "    console.log(42)",
+                "}",
+            ].join("\n"),
+        ].forEach(function(code) {
+            assert.throws(function() {
+                UglifyJS.parse(code);
+            }, function(e) {
+                return e instanceof UglifyJS.JS_Parse_Error;
+            }, code);
+        });
+    });
 });
--- a/test/mocha/minify.js
+++ b/test/mocha/minify.js
@@ -25,7 +25,7 @@ describe("minify", function() {
        if (result.error) throw result.error;
        assert.strictEqual(result.code, "print(42);");
        assert.strictEqual(JSON.stringify(options), value);
-    })
+    });
    it("Should skip inherited keys from `files`", function() {
        var files = Object.create({ skip: this });
        files[0] = "alert(1 + 1)";
--- a/test/mocha/reduce.js
+++ b/test/mocha/reduce.js
@@ -1,5 +1,4 @@
 var assert = require("assert");
-var exec = require("child_process").exec;
 var fs = require("fs");
 var reduce_test = require("../reduce");
 var semver = require("semver");
@@ -183,6 +182,24 @@ describe("test/reduce.js", function() {
            "// }",
        ].join("\n"));
    });
+    it("Should reduce `for (const ... in ...)` without invalid intermediate AST", function() {
+        if (semver.satisfies(process.version, "<4")) return;
+        var code = [
+            "var a = 0;",
+            "",
+            "for (const b in [ 1, 2, 3 ]) {",
+            "    a = +a + 1 - .2;",
+            "    console.log(a);",
+            "}",
+        ].join("\n");
+        var result = reduce_test(code, {
+            compress: {
+                unsafe_math: true,
+            },
+        });
+        if (result.error) throw result.error;
+        assert.deepEqual(result.warnings, []);
+    });
    it("Should reduce infinite loops with reasonable performance", function() {
        if (semver.satisfies(process.version, "<=0.10")) return;
        this.timeout(120000);
@@ -264,35 +281,40 @@ describe("test/reduce.js", function() {
        });
        if (result.error) throw result.error;
        assert.deepEqual(result.warnings, []);
-        assert.strictEqual(result.code.replace(/function \(/g, "function("), (semver.satisfies(process.version, "<=0.10") ? [
-            "// Can't reproduce test failure",
-            "// minify options: {",
-            '//   "compress": false,',
-            '//   "mangle": false,',
-            '//   "output": {',
-            '//     "beautify": true',
-            "//   }",
-            "// }",
-        ] : [
-            [
-                "try{",
-                "null[function(){}]",
-                "}catch(e){",
-                "console.log(e)",
-                "}",
-            ].join(""),
-            "// output: TypeError: Cannot read property 'function(){}' of null",
-            "// ",
-            "// minify: TypeError: Cannot read property 'function() {}' of null",
-            "// ",
-            "// options: {",
-            '//   "compress": false,',
-            '//   "mangle": false,',
-            '//   "output": {',
-            '//     "beautify": true',
-            "//   }",
-            "// }",
-        ]).join("\n"));
+        if (semver.satisfies(process.version, "<=0.10")) {
+            assert.strictEqual(result.code, [
+                "// Can't reproduce test failure",
+                "// minify options: {",
+                '//   "compress": false,',
+                '//   "mangle": false,',
+                '//   "output": {',
+                '//     "beautify": true',
+                "//   }",
+                "// }",
+            ].join("\n"));
+        } else {
+            var message = result.code.split(/\n/, 3)[1].slice("// output: ".length);
+            assert.strictEqual(result.code, [
+                [
+                    "try{",
+                    "null[function(){}]",
+                    "}catch(e){",
+                    "console.log(e)",
+                    "}",
+                ].join(""),
+                "// output: " + message,
+                "// ",
+                "// minify: " + message.replace("(){}", "() {}"),
+                "// ",
+                "// options: {",
+                '//   "compress": false,',
+                '//   "mangle": false,',
+                '//   "output": {',
+                '//     "beautify": true',
+                "//   }",
+                "// }",
+            ].join("\n"));
+        }
    });
    it("Should maintain block-scope for const/let", function() {
        if (semver.satisfies(process.version, "<4")) return;
@@ -361,4 +383,55 @@ describe("test/reduce.js", function() {
        if (result.error) throw result.error;
        assert.strictEqual(result.code, read("test/input/reduce/destructured_catch.reduced.js"));
    });
+    it("Should not enumerate `toString` over global context", function() {
+        if (semver.satisfies(process.version, "<8")) return;
+        var code = [
+            "(async function() {});",
+            "for (var k in this);",
+            "console.log(k, 42 + this);",
+        ].join("\n");
+        var result = reduce_test(code, {
+            mangle: false,
+        });
+        if (result.error) throw result.error;
+        assert.strictEqual(result.code, [
+            "// Can't reproduce test failure",
+            "// minify options: {",
+            '//   "mangle": false',
+            "// }",
+        ].join("\n"));
+    });
+    it("Should reduce object with method syntax without invalid intermediate AST", function() {
+        if (semver.satisfies(process.version, "<4")) return;
+        var code = [
+            "console.log({",
+            "    f() {",
+            "        return 1 - .8;",
+            "    },",
+            "}.f());",
+        ].join("\n");
+        var result = reduce_test(code, {
+            compress: {
+                unsafe_math: true,
+            },
+        });
+        if (result.error) throw result.error;
+        assert.deepEqual(result.warnings, []);
+    });
+    it("Should handle thrown falsy values gracefully", function() {
+        var code = [
+            "throw 0;",
+            "setTimeout(null, 42);",
+        ].join("\n");
+        var result = reduce_test(code, {
+            mangle: false,
+        });
+        if (result.error) throw result.error;
+        assert.strictEqual(result.code, [
+            "// Can't reproduce test failure",
+            "// minify options: {",
+            '//   "mangle": false',
+            "// }",
+        ].join("\n"));
+    });
 });
--- a/test/mocha/sourcemaps.js
+++ b/test/mocha/sourcemaps.js
@@ -101,6 +101,19 @@ describe("sourcemaps", function() {
        var map = JSON.parse(result.map);
        assert.deepEqual(map.names, []);
    });
+    it("Should mark class properties", function() {
+        var result = UglifyJS.minify([
+            "class A {",
+            "    static P = 42",
+            "    set #q(v) {}",
+            "}",
+        ].join("\n"), {
+            sourceMap: true,
+        });
+        if (result.error) throw result.error;
+        assert.strictEqual(result.code, "class A{static P=42;set#q(s){}}");
+        assert.strictEqual(result.map, '{"version":3,"sources":["0"],"names":["A","P","#q","v"],"mappings":"MAAMA,EACFC,SAAW,GACXC,MAAOC"}');
+    });
    it("Should mark array/object literals", function() {
        var result = UglifyJS.minify([
            "var obj = {};",
@@ -192,8 +205,8 @@ describe("sourcemaps", function() {
            });
            if (result.error) throw result.error;
            assert.strictEqual(result.code, [
-                "var Foo=function(){console.log(3)};new Foo;var bar=function(o){return o};",
-                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInN0ZGluIiwiMSJdLCJuYW1lcyI6WyJGb28iLCJjb25zb2xlIiwibG9nIiwiYmFyIl0sIm1hcHBpbmdzIjoiQUFBQSxJQUFNQSxJQUFJLFdBQWdCQyxRQUFRQyxJQUFJLElBQVMsSUFBSUYsSUNBbkQsSUFBSUcsSUFDQSxTQUFjQSxHQUNWLE9BQU9BIn0=",
+                "var Foo=function(){console.log(3)},bar=(new Foo,function(o){return o});",
+                "//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInN0ZGluIiwiMSJdLCJuYW1lcyI6WyJGb28iLCJjb25zb2xlIiwibG9nIiwiYmFyIl0sIm1hcHBpbmdzIjoiQUFBQSxJQUFNQSxJQUFJLFdBQWdCQyxRQUFRQyxJQUFJLElDQWxDQyxLREEyQyxJQUFJSCxJQ0MvQyxTQUFjRyxHQUNWLE9BQU9BIn0=",
            ].join("\n"));
            assert.deepEqual(result.warnings, [ "WARN: inline source map not found: 1" ]);
        });
@@ -349,7 +362,7 @@ describe("sourcemaps", function() {
        it("Should not modify input source map", function() {
            var orig = get_map();
            var original = JSON.stringify(orig);
-            var map = prepare_map(orig);
+            prepare_map(orig);
            assert.strictEqual(JSON.stringify(orig), original);
        });
        it("Should copy over original sourcesContent", function() {
--- a/test/mocha/spidermonkey.js
+++ b/test/mocha/spidermonkey.js
@@ -1,37 +1,42 @@
 var assert = require("assert");
 var exec = require("child_process").exec;
+var semver = require("semver");
 var UglifyJS = require("../..");

 describe("spidermonkey export/import sanity test", function() {
    it("Should produce a functional build when using --self with spidermonkey", function(done) {
-        this.timeout(60000);
-
+        this.timeout(120000);
        var uglifyjs = '"' + process.argv[0] + '" bin/uglifyjs';
-        var command = uglifyjs + " --self -cm --wrap SpiderUglify -o spidermonkey | " +
-            uglifyjs + " -p spidermonkey -cm";
-
-        exec(command, {
-            maxBuffer: 1048576
-        }, function(err, stdout) {
+        var options = semver.satisfies(process.version, "<=0.12") ? "-mc hoist_funs" : "-mc";
+        var command = [
+            [
+                uglifyjs,
+                "--self",
+                options,
+                "--wrap SpiderUglify",
+                "-o spidermonkey",
+            ].join(" "),
+            [
+                uglifyjs,
+                "-p spidermonkey",
+                options,
+            ].join(" "),
+        ].join(" | ");
+        exec(command, { maxBuffer: 1048576 }, function(err, stdout) {
            if (err) throw err;
-
            eval(stdout);
            assert.strictEqual(typeof SpiderUglify, "object");
            var result = SpiderUglify.minify("foo([true,,2+3]);");
            assert.strictEqual(result.error, undefined);
            assert.strictEqual(result.code, "foo([!0,,5]);");
-
            done();
        });
    });

-    it("Should not add unnecessary escape slashes to regexps", function() {
+    it("Should not add unnecessary escape slashes to RegExp", function() {
        var input = "/[\\\\/]/;";
        var ast = UglifyJS.parse(input).to_mozilla_ast();
-        assert.equal(
-            UglifyJS.AST_Node.from_mozilla_ast(ast).print_to_string(),
-            input
-        );
+        assert.strictEqual(UglifyJS.AST_Node.from_mozilla_ast(ast).print_to_string(), input);
    });

    it("Should judge between directives and strings correctly on import", function() {
--- a/test/mocha/string-literal.js
+++ b/test/mocha/string-literal.js
@@ -12,7 +12,7 @@ describe("String literals", function() {
            '"\u2029"',
        ].forEach(function(input) {
            assert.throws(function() {
-                var ast = UglifyJS.parse(input);
+                UglifyJS.parse(input);
            }, function(e) {
                return e instanceof UglifyJS.JS_Parse_Error
                    && e.message === "Unterminated string constant";
@@ -44,7 +44,7 @@ describe("String literals", function() {
            '"use strict";\n"\\011"',
        ].forEach(function(input) {
            assert.throws(function() {
-                var output = UglifyJS.parse(input);
+                UglifyJS.parse(input);
            }, function(e) {
                return e instanceof UglifyJS.JS_Parse_Error
                    && e.message === "Legacy octal escape sequences are not allowed in strict mode";
--- a/test/mocha/templates.js
+++ b/test/mocha/templates.js
@@ -34,20 +34,20 @@ describe("Template literals", function() {
        [
            // native line breaks
            [ "`foo\nbar`", "`foo\nbar`" ],
-            [ "`foo\rbar`", "`foo\rbar`" ],
+            [ "`foo\rbar`", "`foo\nbar`" ],
            [ "`foo\r\nbar`", "`foo\nbar`" ],
-            [ "`foo\r\n\rbar`", "`foo\n\rbar`" ],
+            [ "`foo\r\n\rbar`", "`foo\n\nbar`" ],
            // escaped line breaks
            [ "`foo\\nbar`", "`foo\\nbar`" ],
            [ "`foo\\rbar`", "`foo\\rbar`" ],
-            [ "`foo\r\\nbar`", "`foo\r\\nbar`" ],
+            [ "`foo\r\\nbar`", "`foo\n\\nbar`" ],
            [ "`foo\\r\nbar`", "`foo\\r\nbar`" ],
            [ "`foo\\r\\nbar`", "`foo\\r\\nbar`" ],
            // continuation
            [ "`foo\\\nbar`", "`foo\\\nbar`" ],
-            [ "`foo\\\rbar`", "`foo\\\rbar`" ],
+            [ "`foo\\\rbar`", "`foo\\\nbar`" ],
            [ "`foo\\\r\nbar`", "`foo\\\nbar`" ],
-            [ "`foo\\\r\n\rbar`", "`foo\\\n\rbar`" ],
+            [ "`foo\\\r\n\rbar`", "`foo\\\n\nbar`" ],
            [ "`foo\\\\nbar`", "`foo\\\\nbar`" ],
            [ "`foo\\\\rbar`", "`foo\\\\rbar`" ],
            [ "`foo\\\\r\nbar`", "`foo\\\\r\nbar`" ],
--- a/test/mozilla-ast.js
+++ b/test/mozilla-ast.js
@@ -5,23 +5,23 @@ var acorn = require("acorn");
 var ufuzz = require("./ufuzz");
 var UglifyJS = require("..");

-function try_beautify(code) {
-    var beautified = UglifyJS.minify(code, {
+function beautify(ast) {
+    var beautified = UglifyJS.minify(ast, {
        compress: false,
        mangle: false,
        output: {
            beautify: true,
-            braces: true
-        }
+            braces: true,
+        },
+    });
+    if (beautified.error) return beautified;
+    return UglifyJS.minify(beautified.code, {
+        compress: false,
+        mangle: false,
+        output: {
+            ast: true,
+        },
    });
-    if (beautified.error) {
-        console.log("// !!! beautify failed !!!");
-        console.log(beautified.error.stack);
-        console.log(code);
-    } else {
-        console.log("// (beautified)");
-        console.log(beautified.code);
-    }
 }

 function validate(ast) {
@@ -35,16 +35,55 @@ function validate(ast) {
    return UglifyJS.minify(ast, {
        compress: false,
        mangle: false,
+        output: {
+            ast: true,
+        },
+        validate: true,
    });
 }

-function test(original, estree, description) {
-    var transformed = validate(UglifyJS.AST_Node.from_mozilla_ast(estree));
-    if (transformed.error || original !== transformed.code) {
+function patch_import(code) {
+    return code.replace(/\bimport\s*\{\s*\}\s*from\s*(['"])/g, "import$1")
+        .replace(/\b(import\b.*?)\s*,\s*\{\s*\}\s*(from\s*['"])/g, "$1 $2");
+}
+
+function equals(input, transformed) {
+    if (input.code === transformed.code) return true;
+    return patch_import(input.code) === patch_import(transformed.code);
+}
+
+function test(input, to_moz, description, skip_on_error, beautified) {
+    try {
+        var ast = UglifyJS.AST_Node.from_mozilla_ast(to_moz(input));
+    } catch (e) {
+        if (skip_on_error) return true;
+        console.log("//=============================================================");
+        console.log("//", description, "failed... round", round);
+        console.log(e);
+        console.log("// original code");
+        if (beautified === true) console.log("// (beautified)");
+        console.log(input.code);
+        return false;
+    }
+    var transformed = validate(ast);
+    if (transformed.error || !equals(input, transformed)) {
+        if (!beautified) {
+            beautified = beautify(input.ast);
+            if (!beautified.error) {
+                beautified.raw = beautified.code;
+                if (!test(beautified, to_moz, description, skip_on_error, true)) return false;
+            }
+        }
        console.log("//=============================================================");
        console.log("// !!!!!! Failed... round", round);
        console.log("// original code");
-        try_beautify(original);
+        if (beautified.error) {
+            console.log("// !!! beautify failed !!!");
+            console.log(beautified.error.stack);
+        } else if (beautified === true) {
+            console.log("// (beautified)");
+        }
+        console.log(input.raw);
        console.log();
        console.log();
        console.log("//-------------------------------------------------------------");
@@ -52,7 +91,15 @@ function test(original, estree, description) {
        if (transformed.error) {
            console.log(transformed.error.stack);
        } else {
-            try_beautify(transformed.code);
+            beautified = beautify(transformed.ast);
+            if (beautified.error) {
+                console.log("// !!! beautify failed !!!");
+                console.log(beautified.error.stack);
+                console.log(transformed.code);
+            } else {
+                console.log("// (beautified)");
+                console.log(beautified.code);
+            }
        }
        console.log("!!!!!! Failed... round", round);
        return false;
@@ -67,24 +114,33 @@ for (var round = 1; round <= num_iterations; round++) {
    process.stdout.write(round + " of " + num_iterations + "\r");
    var code = ufuzz.createTopLevelCode();
    minify_options.forEach(function(options) {
-        var input = options ? UglifyJS.minify(code, JSON.parse(options)).code : code;
-        var uglified = UglifyJS.minify(input, {
+        var ok = true;
+        var input = UglifyJS.minify(options ? UglifyJS.minify(code, JSON.parse(options)).code : code, {
            compress: false,
            mangle: false,
            output: {
-                ast: true
-            }
+                ast: true,
+            },
        });
-        var ok = test(uglified.code, uglified.ast.to_mozilla_ast(), "AST_Node.to_mozilla_ast()");
-        try {
-            ok = test(uglified.code, acorn.parse(input), "acorn.parse()") && ok;
-        } catch (e) {
+        input.raw = options ? input.code : code;
+        if (input.error) {
+            ok = false;
            console.log("//=============================================================");
-            console.log("// acorn parser failed... round", round);
-            console.log(e);
+            console.log("// minify() failed... round", round);
+            console.log(input.error);
            console.log("// original code");
-            console.log(input);
+            console.log(code);
        }
+        if (ok) ok = test(input, function(input) {
+            return input.ast.to_mozilla_ast();
+        }, "AST_Node.to_mozilla_ast()");
+        if (ok) ok = test(input, function(input) {
+            return acorn.parse(input.raw, {
+                ecmaVersion: "latest",
+                locations: true,
+                sourceType: "module",
+            });
+        }, "acorn.parse()", !ufuzz.verbose);
        if (!ok) process.exit(1);
    });
 }
--- a/test/reduce.js
+++ b/test/reduce.js
@@ -22,7 +22,7 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
    reduce_options = reduce_options || {};
    var print_options = {};
    [
-        "ie8",
+        "ie",
        "v8",
        "webkit",
    ].forEach(function(name) {
@@ -46,7 +46,7 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
    if (verbose) {
        log("// Node.js " + process.version + " on " + os.platform() + " " + os.arch());
    }
-    if (differs.error && [ "DefaultsError", "SyntaxError" ].indexOf(differs.error.name) < 0) {
+    if (differs && differs.error && [ "DefaultsError", "SyntaxError" ].indexOf(differs.error.name) < 0) {
        test_for_diff = test_minify;
        differs = test_for_diff(testcase, minify_options, result_cache, max_timeout);
    }
@@ -132,6 +132,8 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                return;
            }
            if (parent instanceof U.AST_VarDef && parent.name === node) return;
+            // preserve class methods
+            if (parent instanceof U.AST_ClassMethod && parent.value === node) return;
            // preserve exports
            if (parent instanceof U.AST_ExportDeclaration) return;
            if (parent instanceof U.AST_ExportDefault) return;
@@ -147,6 +149,9 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
            if (parent instanceof U.AST_For && parent.init === node && node instanceof U.AST_Definitions) return node;
            // preserve for (xxx in/of ...)
            if (parent instanceof U.AST_ForEnumeration && parent.init === node) return node;
+            // preserve super(...)
+            if (node.TYPE == "Call" && node.expression instanceof U.AST_Super) return;
+            if (node instanceof U.AST_Super && parent.TYPE == "Call" && parent.expression === node) return node;

            // node specific permutations with no parent logic

@@ -210,9 +215,9 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                    // hoist and return expressions from the IIFE function expression
                    var seq = [];
                    node.expression.body.forEach(function(node) {
-                        var expr = expr instanceof U.AST_Exit ? node.value : node.body;
+                        var expr = node instanceof U.AST_Exit ? node.value : node.body;
                        if (expr instanceof U.AST_Node && !U.is_statement(expr) && can_hoist(expr)) {
-                            // collect expressions from each statements' body
+                            // collect expressions from each statement's body
                            seq.push(expr);
                        }
                    });
@@ -316,10 +321,11 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                var expr;
                switch ((node.start._permute * steps | 0) % 3) {
                  case 0:
-                    if (!(node.init instanceof U.AST_Definitions
-                        && node.init.definitions[0].name instanceof U.AST_Destructured)) {
-                        expr = node.init;
+                    if (node.init instanceof U.AST_Definitions) {
+                        if (node.init instanceof U.AST_Const) break;
+                        if (node.init.definitions[0].name instanceof U.AST_Destructured) break;
                    }
+                    expr = node.init;
                    break;
                  case 1:
                    expr = node.object;
@@ -389,7 +395,7 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                var expr = [
                    node.expression,                         // switch expression
                    node.body[0] && node.body[0].expression, // first case expression or undefined
-                    node.body[0] && node.body[0],            // first case body or undefined
+                    node.body[0],                            // first case body or undefined
                ][ (node.start._permute * steps | 0) % 4 ];
                node.start._permute += step;
                if (expr && (!(expr instanceof U.AST_Statement) || !has_loopcontrol(expr, node, parent))) {
@@ -484,23 +490,27 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
            CHANGED = true;
            return newNode;
        }, function(node, in_list) {
-            if (node instanceof U.AST_Sequence) {
+            if (node instanceof U.AST_Definitions) {
+                // remove empty var statement
+                if (node.definitions.length == 0) return in_list ? List.skip : new U.AST_EmptyStatement({
+                    start: {},
+                });
+            } else if (node instanceof U.AST_ObjectMethod) {
+                if (!/Function$/.test(node.value.TYPE)) return new U.AST_ObjectKeyVal({
+                    key: node.key,
+                    value: node.value,
+                    start: {},
+                });
+            } else if (node instanceof U.AST_Sequence) {
                // expand single-element sequence
                if (node.expressions.length == 1) return node.expressions[0];
-            }
-            else if (node instanceof U.AST_Try) {
+            } else if (node instanceof U.AST_Try) {
                // expand orphaned try block
                if (!node.bcatch && !node.bfinally) return new U.AST_BlockStatement({
                    body: node.body,
                    start: {},
                });
            }
-            else if (node instanceof U.AST_Definitions) {
-                // remove empty var statement
-                if (node.definitions.length == 0) return in_list ? List.skip : new U.AST_EmptyStatement({
-                    start: {},
-                });
-            }
        });

        var diff_error_message;
@@ -538,7 +548,7 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
            }));
            var before_iterations = testcase;
            for (var c = 0; c < max_iterations; ++c) {
-                if (verbose && pass == 1 && c % 25 == 0) {
+                if (verbose && c % (pass == 1 ? 25 : 100) == 0) {
                    log("// reduce test pass " + pass + ", iteration " + c + ": " + testcase.length + " bytes");
                }
                var CHANGED = false;
@@ -716,7 +726,7 @@ function to_statement_init(node) {
    return node instanceof U.AST_Const || node instanceof U.AST_Let ? new U.AST_BlockStatement({
        body: [ node ],
        start: {},
-    }) : to_statement(node);;
+    }) : to_statement(node);
 }

 function wrap_with_console_log(node) {
--- a/test/release/acorn.sh
+++ b/test/release/acorn.sh
@@ -14,6 +14,13 @@ minify_in_situ() {
    uglify-js $ARGS
 }

+npm_install() {
+    PKG="$1"
+    while !(npm install $PKG); do
+        while !(npm cache clean --force); do echo "'npm cache clean' failed - retrying..."; done
+    done
+}
+
 rm -rf tmp/acorn \
 && git clone https://github.com/acornjs/acorn.git tmp/acorn \
 && cd tmp/acorn \
@@ -89,7 +96,7 @@ minify_in_situ "acorn/src" \
 && minify_in_situ "acorn-loose/src" \
 && minify_in_situ "acorn-walk/src" \
 && rm -rf node_modules \
-&& npm install \
+&& npm_install \
 && rm -rf acorn/dist acorn-loose/dist acorn-walk/dist \
 && npm run build \
 && minify_in_situ "acorn/dist" \
--- a/test/release/bootstrap.sh
+++ b/test/release/bootstrap.sh
@@ -14,6 +14,13 @@ minify_in_situ() {
    uglify-js $ARGS
 }

+npm_install() {
+    PKG="$1"
+    while !(npm install $PKG); do
+        while !(npm cache clean --force); do echo "'npm cache clean' failed - retrying..."; done
+    done
+}
+
 rm -rf tmp/bootstrap \
 && git clone --depth 1 --branch v5.0.0-beta2 https://github.com/twbs/bootstrap.git tmp/bootstrap \
 && cd tmp/bootstrap \
@@ -171,7 +178,7 @@ rm -rf tmp/bootstrap \
 EOF
 ERR=$?; if [ "$ERR" != "0" ]; then echo "Error: $ERR"; exit $ERR; fi
 rm -rf node_modules \
-&& npm ci \
+&& npm_install \
 && minify_in_situ "node_modules/@popperjs/core" \
 && rm -rf dist/js/* \
 && minify_in_situ "build" \
--- a/test/release/buble.sh
+++ b/test/release/buble.sh
@@ -14,6 +14,13 @@ minify_in_situ() {
    uglify-js $ARGS
 }

+npm_install() {
+    PKG="$1"
+    while !(npm install $PKG); do
+        while !(npm cache clean --force); do echo "'npm cache clean' failed - retrying..."; done
+    done
+}
+
 rm -rf tmp/buble \
 && git clone https://github.com/bublejs/buble.git tmp/buble \
 && cd tmp/buble \
@@ -38,7 +45,7 @@ EOF
 ERR=$?; if [ "$ERR" != "0" ]; then echo "Error: $ERR"; exit $ERR; fi
 minify_in_situ "src" \
 && rm -rf node_modules \
-&& npm ci \
+&& npm_install \
 && rm -rf dist \
 && npm run build \
 && minify_in_situ "dist" \
--- a/test/release/butternut.sh
+++ b/test/release/butternut.sh
@@ -14,6 +14,13 @@ minify_in_situ() {
    uglify-js $ARGS
 }

+npm_install() {
+    PKG="$1"
+    while !(npm install $PKG); do
+        while !(npm cache clean --force); do echo "'npm cache clean' failed - retrying..."; done
+    done
+}
+
 rm -rf tmp/butternut \
 && git clone https://github.com/Rich-Harris/butternut.git tmp/butternut \
 && cd tmp/butternut \
@@ -38,7 +45,7 @@ EOF
 ERR=$?; if [ "$ERR" != "0" ]; then echo "Error: $ERR"; exit $ERR; fi
 minify_in_situ "src" \
 && rm -rf node_modules \
-&& npm install \
+&& npm_install \
 && rm -rf dist \
 && npm run build \
 && minify_in_situ "dist" \
--- a/test/release/install.sh
+++ b/test/release/install.sh
@@ -1,3 +1,24 @@
+echo "::group::GitHub Environment Variables"
+echo "CI: $CI"
+echo "GITHUB_WORKFLOW: $GITHUB_WORKFLOW"
+echo "GITHUB_RUN_ID: $GITHUB_RUN_ID"
+echo "GITHUB_RUN_NUMBER: $GITHUB_RUN_NUMBER"
+echo "GITHUB_ACTION: $GITHUB_ACTION"
+echo "GITHUB_ACTIONS: $GITHUB_ACTIONS"
+echo "GITHUB_ACTOR: $GITHUB_ACTOR"
+echo "GITHUB_REPOSITORY: $GITHUB_REPOSITORY"
+echo "GITHUB_EVENT_NAME: $GITHUB_EVENT_NAME"
+echo "GITHUB_EVENT_PATH: $GITHUB_EVENT_PATH"
+echo "GITHUB_WORKSPACE: $GITHUB_WORKSPACE"
+echo "GITHUB_SHA: $GITHUB_SHA"
+echo "GITHUB_REF: $GITHUB_REF"
+echo "GITHUB_HEAD_REF: $GITHUB_HEAD_REF"
+echo "GITHUB_BASE_REF: $GITHUB_BASE_REF"
+echo "GITHUB_SERVER_URL: $GITHUB_SERVER_URL"
+echo "GITHUB_API_URL: $GITHUB_API_URL"
+echo "GITHUB_GRAPHQL_URL: $GITHUB_GRAPHQL_URL"
+echo "::endgroup::"
+
 if command -v timeout &> /dev/null; then NATIVE=1; fi
 timeout() {
    T=$1
@@ -15,7 +36,9 @@ EOF
 }
 if [ $NATIVE ]; then unset -f timeout; fi

-git clone --branch v1.6.0 --depth 1 https://github.com/jasongin/nvs.git ~/.nvs
+while !(git clone --branch v1.6.0 --depth 1 https://github.com/jasongin/nvs.git ~/.nvs); do
+    rm -rf ~/.nvs
+done
 while ! timeout 60 bash -c ". ~/.nvs/nvs.sh add $NODE && nvs use $NODE"; do
    cd ~/.nvs
    while !(git clean -xdf); do echo "'git clean' failed - retrying..."; done
@@ -30,4 +53,6 @@ npm config set save false
 npm config set strict-ssl false
 npm config set update-notifier false
 npm --version
-while !(npm install); do echo "'npm install' failed - retrying..."; done
+while !(npm install); do
+    while !(npm cache clean --force); do echo "'npm cache clean' failed - retrying..."; done
+done
--- a/Show More
+++ b/Show More