v3.16.0

fix corner case in comparisons (#5486 )
fixes #5485
2022-06-06 11:29:26 +08:00 · 2022-06-05 00:47:38 +08:00 · 2022-06-02 02:45:02 +08:00 · 2022-06-02 02:44:06 +08:00 · 2022-06-02 02:42:39 +08:00 · 2022-05-31 00:27:40 +08:00
100 changed files with 16296 additions and 3649 deletions
--- 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
@@ -17,13 +17,13 @@ jobs:
      fail-fast: false
      matrix:
        include:
-          - node: latest
+          - node: '16'
            os: macos-latest
-          - node: '8'
+          - node: '12'
            os: ubuntu-latest
          - node: '8'
            os: ubuntu-latest
-          - node: '8'
+          - node: '12'
            os: windows-latest
          - node: '8'
            os: windows-latest
--- a/README.md
+++ b/README.md
@@ -115,8 +115,10 @@ a double dash to prevent input files being used as option arguments:
                                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.
+    --module                    Process input as ES module (implies --toplevel)
    --name-cache <file>         File to hold mangled name mappings.
    --self                      Build UglifyJS as a library (implies --wrap UglifyJS)
    --source-map [options]      Enable source map/specify source map options:
@@ -145,7 +147,7 @@ a double dash to prevent input files being used as option arguments:
    --warn                      Print warning messages.
    --webkit                    Support non-standard Safari/Webkit.
                                Equivalent to setting `webkit: true` in `minify()`
-                                for `mangle` and `output` options.
+                                for `compress`, `mangle` and `output` options.
                                By default UglifyJS will not try to be Safari-proof.
    --wrap <name>               Embed everything in a big function, making the
                                “exports” and “global” variables available. You
@@ -504,6 +506,9 @@ if (result.error) throw result.error;

 - `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`.

@@ -513,6 +518,9 @@ if (result.error) throw result.error;
  - `mangle.properties` (default: `false`) — a subcategory of the mangle option.
    Pass an object to specify custom [mangle property options](#mangle-properties-options).

+- `module` (default: `false`) — set to `true` if you wish to process input as
+  ES module, i.e. implicit `"use strict";` alongside with `toplevel` enabled.
+
 - `nameCache` (default: `null`) — pass an empty object `{}` or a previously
  used `nameCache` object if you wish to cache mangled variable and
  property names across multiple invocations of `minify()`. Note: this is
@@ -707,7 +715,8 @@ 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

@@ -723,6 +732,9 @@ to be `false` and all symbol names will be omitted.

 - `merge_vars` (default: `true`) — combine and reuse variables.

+- `module` (default: `false`) — set to `true` if you wish to process input as
+  ES module, i.e. implicit `"use strict";` alongside with `toplevel` enabled.
+
 - `negate_iife` (default: `true`) — negate "Immediately-Called Function Expressions"
  where the return value is discarded, to avoid the parens that the
  code generator would insert.
@@ -867,6 +879,9 @@ 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
@@ -909,9 +924,11 @@ can pass additional arguments that control the code output:

 - `galio` (default: `false`) — enable workarounds for ANT Galio bugs

- `indent_level` (default: `4`)
+- `indent_level` (default: `4`) — indent by specified number of spaces or the
+  exact whitespace sequence supplied, e.g. `"\t"`.

- `indent_start` (default: `0`) — prefix all lines by that many spaces
+- `indent_start` (default: `0`) — prefix all lines by whitespace sequence
+  specified in the same format as `indent_level`.

 - `inline_script` (default: `true`) — escape HTML comments and the slash in
  occurrences of `</script>` in strings
@@ -1199,6 +1216,17 @@ 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
  ({
@@ -1310,10 +1338,8 @@ To allow for better optimizations, the compiler makes various assumptions:
 - Later versions of JavaScript will throw `SyntaxError` with the following:
  ```javascript
  var await;
-  async function f() {
-      class A {
-          static p = await;
-      }
+  class A {
+      static p = await;
  }
  // SyntaxError: Unexpected reserved word
  ```
@@ -1352,3 +1378,46 @@ To allow for better optimizations, the compiler makes various assumptions:
  // TypeError: const 'a' has already been declared
  ```
  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
+  try {
+      class A {
+          static 42;
+          static get 42() {}
+      }
+      console.log("PASS");
+  } catch (e) {
+      console.log("FAIL");
+  }
+  // Expected: "PASS"
+  // Actual:   "FAIL"
+  ```
+  UglifyJS may modify the input which in turn may suppress those errors.
+- Some versions of Chrome and Node.js will give incorrect results with the
+  following:
+  ```javascript
+  (async function(a) {
+      (function() {
+          var b = await => console.log("PASS");
+          b();
+      })();
+  })().catch(console.error);
+  // Expected: "PASS"
+  // Actual:   SyntaxError: Unexpected reserved word
+  ```
+  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
+  try {
+      f();
+      function f() {
+          throw 42;
+      }
+  } catch (e) {}
+  console.log(typeof f);
+  // Expected: "function"
+  // Actual:   "undefined"
+  ```
+  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 ]);
@@ -102,7 +105,9 @@ function process_option(name, no_value) {
                "  -d, --define <expr>[=value]              Global definitions.",
                "  -e, --enclose [arg[,...][:value[,...]]]  Embed everything in a big function, with configurable argument(s) & value(s).",
                "  --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.",
+                "  --module                                 Process input as ES module (implies --toplevel)",
                "  --name-cache <file>                      File to hold mangled name mappings.",
                "  --rename                                 Force symbol expansion.",
                "  --no-rename                              Disable symbol expansion.",
@@ -148,6 +153,7 @@ function process_option(name, no_value) {
      case "annotations":
      case "ie":
      case "ie8":
+      case "module":
      case "timings":
      case "toplevel":
      case "v8":
@@ -158,6 +164,9 @@ 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;
@@ -430,7 +439,7 @@ 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) {
@@ -519,7 +528,7 @@ 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
@@ -559,8 +568,10 @@ 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
@@ -50,6 +50,8 @@ 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) {
@@ -135,6 +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;
@@ -253,7 +302,7 @@ 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",
@@ -484,7 +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`",
@@ -543,13 +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) {
@@ -778,6 +827,9 @@ var AST_Class = DEFNODE("Class", "extends name properties", {
        extends: "[AST_Node?] the super class, or null if not specified",
        properties: "[AST_ClassProperty*] array of class properties",
    },
+    resolve: function(def_class) {
+        return def_class ? this : this.parent_scope.resolve();
+    },
    walk: function(visitor) {
        var node = this;
        visitor.visit(node, function() {
@@ -1289,13 +1341,14 @@ function must_be_expressions(node, prop, allow_spread, allow_hole) {
    });
 }

-var AST_Call = DEFNODE("Call", "args expression optional 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",
        optional: "[boolean] whether the expression is optional chaining",
-        pure: "[string/S] marker for side-effect-free call expression",
+        pure: "[boolean/S] marker for side-effect-free call expression",
+        terminal: "[boolean] whether the chain has ended",
    },
    walk: function(visitor) {
        var node = this;
@@ -1316,6 +1369,7 @@ var AST_New = DEFNODE("New", null, {
    $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);

@@ -1338,12 +1392,18 @@ var AST_Sequence = DEFNODE("Sequence", "expressions", {
    },
 });

-var AST_PropAccess = DEFNODE("PropAccess", "expression optional 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",
        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",
    },
    get_property: function() {
        var p = this.property;
@@ -1481,6 +1541,12 @@ 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);
@@ -1739,7 +1805,7 @@ 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);

@@ -1771,7 +1837,7 @@ var AST_Label = DEFNODE("Label", "references", {
    initialize: function() {
        this.references = [];
        this.thedef = this;
-    }
+    },
 }, AST_Symbol);

 var AST_SymbolRef = DEFNODE("SymbolRef", "fixed in_arg redef", {
@@ -1915,27 +1981,27 @@ 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, {
@@ -1947,12 +2013,12 @@ 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 ]----- */
@@ -1973,16 +2039,21 @@ TreeWalker.prototype = {
        return this.stack[this.stack.length - 2 - (n || 0)];
    },
    push: function(node) {
-        if (node instanceof AST_Lambda) {
+        var value;
+        if (node instanceof AST_Class) {
+            this.directives = Object.create(this.directives);
+            value = "use strict";
+        } else if (node instanceof AST_Directive) {
+            value = node.value;
+        } else if (node instanceof AST_Lambda) {
            this.directives = Object.create(this.directives);
-        } else if (node instanceof AST_Directive && !this.directives[node.value]) {
-            this.directives[node.value] = node;
        }
+        if (value && !this.directives[value]) this.directives[value] = node;
        this.stack.push(node);
    },
    pop: function() {
        var node = this.stack.pop();
-        if (node instanceof AST_Lambda) {
+        if (node instanceof AST_Class || node instanceof AST_Lambda) {
            this.directives = Object.getPrototypeOf(this.directives);
        }
    },
@@ -1991,7 +2062,7 @@ 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;
        }
@@ -2022,33 +2093,40 @@ TreeWalker.prototype = {
        }
    },
    in_boolean_context: function() {
-        var self = this.self();
-        for (var i = 0, p; p = this.parent(i); i++) {
-            if (p instanceof AST_Conditional && p.condition === self
-                || p instanceof AST_DWLoop && p.condition === self
-                || p instanceof AST_For && p.condition === self
-                || p instanceof AST_If && p.condition === self
-                || p instanceof AST_Return && p.in_bool
-                || p instanceof AST_Sequence && p.tail_node() !== self
-                || p instanceof AST_SimpleStatement
-                || p instanceof AST_UnaryPrefix && p.operator == "!" && p.expression === self) {
-                return true;
-            }
-            if (p instanceof AST_Binary && (p.operator == "&&" || p.operator == "||")
-                || p instanceof AST_Conditional
-                || p.tail_node() === self) {
-                self = p;
-            } else if (p instanceof AST_Return) {
-                for (var call, fn = p; call = this.parent(++i); fn = call) {
-                    if (call.TYPE == "Call") {
-                        if (!(fn instanceof AST_Lambda) || fn.name) return false;
-                    } else if (fn instanceof AST_Lambda) {
-                        return false;
-                    }
-                }
-            } else {
+        for (var drop = true, level = 0, parent, self = this.self(); parent = this.parent(level++); self = parent) {
+            if (parent instanceof AST_Binary) switch (parent.operator) {
+              case "&&":
+              case "||":
+                if (parent.left === self) drop = false;
+                continue;
+              default:
                return false;
            }
+            if (parent instanceof AST_Conditional) {
+                if (parent.condition === self) return true;
+                continue;
+            }
+            if (parent instanceof AST_DWLoop) return parent.condition === self;
+            if (parent instanceof AST_For) return parent.condition === self;
+            if (parent instanceof AST_If) return parent.condition === self;
+            if (parent instanceof AST_Return) {
+                if (parent.in_bool) return true;
+                while (parent = this.parent(level++)) {
+                    if (parent instanceof AST_Lambda) {
+                        if (parent.name) return false;
+                        parent = this.parent(level++);
+                        if (parent.TYPE != "Call") return false;
+                        break;
+                    }
+                }
+            }
+            if (parent instanceof AST_Sequence) {
+                if (parent.tail_node() === self) continue;
+                return drop ? "d" : true;
+            }
+            if (parent instanceof AST_SimpleStatement) return drop ? "d" : true;
+            if (parent instanceof AST_UnaryPrefix) return parent.operator == "!";
+            return false;
        }
    }
 };
--- 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]);
        }
@@ -78,15 +78,17 @@ function minify(files, options) {
            enclose: false,
            ie: false,
            ie8: false,
+            keep_fargs: false,
            keep_fnames: false,
            mangle: {},
+            module: false,
            nameCache: null,
            output: {},
            parse: {},
            rename: undefined,
            sourceMap: false,
            timings: false,
-            toplevel: false,
+            toplevel: !!(options && options["module"]),
            v8: false,
            validate: false,
            warnings: false,
@@ -95,19 +97,22 @@ function minify(files, options) {
        }, true);
        if (options.validate) AST_Node.enable_validation();
        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.ie || options.ie8) set_shorthand("ie", options, [ "compress", "mangle", "output" ]);
-        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, [ "compress", "mangle", "output" ]);
+        if (options.ie8) options.ie = options.ie || options.ie8;
+        if (options.ie) set_shorthand("ie", options, [ "compress", "mangle", "output", "rename" ]);
+        if (options.keep_fargs) set_shorthand("keep_fargs", options, [ "compress", "mangle", "rename" ]);
+        if (options.keep_fnames) set_shorthand("keep_fnames", options, [ "compress", "mangle", "rename" ]);
+        if (options.module) set_shorthand("module", options, [ "compress", "parse" ]);
+        if (options.toplevel) set_shorthand("toplevel", options, [ "compress", "mangle", "rename" ]);
+        if (options.v8) set_shorthand("v8", options, [ "mangle", "output", "rename" ]);
+        if (options.webkit) set_shorthand("webkit", options, [ "compress", "mangle", "output", "rename" ]);
        var quoted_props;
        if (options.mangle) {
            options.mangle = defaults(options.mangle, {
                cache: options.nameCache && (options.nameCache.vars || {}),
                eval: false,
                ie: false,
+                keep_fargs: false,
                keep_fnames: false,
                properties: false,
                reserved: [],
@@ -131,6 +136,7 @@ function minify(files, options) {
            init_cache(options.mangle.cache);
            init_cache(options.mangle.properties.cache);
        }
+        if (options.rename === undefined) options.rename = options.compress && options.mangle;
        if (options.sourceMap) {
            options.sourceMap = defaults(options.sourceMap, {
                content: null,
@@ -186,8 +192,8 @@ function minify(files, options) {
        if (options.validate) toplevel.validate_ast();
        if (timings) timings.rename = Date.now();
        if (options.rename) {
-            toplevel.figure_out_scope(options.mangle);
-            toplevel.expand_names(options.mangle);
+            toplevel.figure_out_scope(options.rename);
+            toplevel.expand_names(options.rename);
        }
        if (timings) timings.compress = Date.now();
        if (options.compress) {
--- a/lib/mozilla-ast.js
+++ b/lib/mozilla-ast.js
@@ -556,7 +556,9 @@
            return node;
        },
        ChainExpression: function(M) {
-            return from_moz(M.expression);
+            var node = from_moz(M.expression);
+            node.terminal = true;
+            return node;
        },
    };

@@ -868,7 +870,7 @@

    def_to_moz(AST_PropAccess, function To_Moz_MemberExpression(M) {
        var computed = M instanceof AST_Sub;
-        return {
+        var expr = {
            type: "MemberExpression",
            object: to_moz(M.expression),
            computed: computed,
@@ -878,6 +880,10 @@
                name: M.property,
            },
        };
+        return M.terminal ? {
+            type: "ChainExpression",
+            expression: expr,
+        } : expr;
    });

    def_to_moz(AST_Unary, function To_Moz_Unary(M) {
@@ -999,7 +1005,7 @@
    });

    def_to_moz(AST_RegExp, function To_Moz_RegExpLiteral(M) {
-        var flags = M.value.toString().match(/[gimuy]*$/)[0];
+        var flags = M.value.toString().match(/\/([gimuy]*)$/)[1];
        var value = "/" + M.value.raw_source + "/" + flags;
        return {
            type: "Literal",
@@ -1007,8 +1013,8 @@
            raw: value,
            regex: {
                pattern: M.value.raw_source,
-                flags: flags
-            }
+                flags: flags,
+            },
        };
    });

--- a/lib/output.js
+++ b/lib/output.js
@@ -101,10 +101,18 @@ function OutputStream(options) {
        }
    }

+    function make_indent(value) {
+        if (typeof value == "number") return new Array(value + 1).join(" ");
+        if (!value) return "";
+        if (!/^\s*$/.test(value)) throw new Error("unsupported indentation: " + JSON.stringify("" + value));
+        return value;
+    }
+
    var current_col = 0;
    var current_line = 1;
-    var current_pos = 0;
-    var indentation = options.indent_start;
+    var current_indent = make_indent(options.indent_start);
+    var full_indent = make_indent(options.indent_level);
+    var half_indent = full_indent.length + 1 >> 1;
    var last;
    var line_end = 0;
    var line_fixed = true;
@@ -115,17 +123,17 @@ function OutputStream(options) {
    var might_need_semicolon;
    var need_newline_indented = false;
    var need_space = false;
-    var newline_insert = -1;
+    var output;
    var stack;
-    var OUTPUT;
+    var stored = "";

    function reset() {
        last = "";
        might_need_space = false;
        might_need_semicolon = false;
        stack = [];
-        var str = OUTPUT;
-        OUTPUT = "";
+        var str = output;
+        output = "";
        return str;
    }

@@ -227,32 +235,30 @@ function OutputStream(options) {
    } : noop;

    function insert_newlines(count) {
-        var index = OUTPUT.lastIndexOf("\n");
-        if (line_end < index) line_end = index;
-        var left = OUTPUT.slice(0, line_end);
-        var right = OUTPUT.slice(line_end);
-        adjust_mappings(count, right.length - current_col);
+        stored += output.slice(0, line_end);
+        output = output.slice(line_end);
+        var new_col = output.length;
+        adjust_mappings(count, new_col - current_col);
        current_line += count;
-        current_pos += count;
-        current_col = right.length;
-        OUTPUT = left;
-        while (count--) OUTPUT += "\n";
-        OUTPUT += right;
+        current_col = new_col;
+        while (count--) stored += "\n";
    }

-    var fix_line = options.max_line_len ? function() {
+    var fix_line = options.max_line_len ? function(flush) {
        if (line_fixed) {
            if (current_col > options.max_line_len) {
                AST_Node.warn("Output exceeds {max_line_len} characters", options);
            }
            return;
        }
-        if (current_col > options.max_line_len) insert_newlines(1);
-        line_fixed = true;
-        flush_mappings();
+        if (current_col > options.max_line_len) {
+            insert_newlines(1);
+            line_fixed = true;
+        }
+        if (line_fixed || flush) flush_mappings();
    } : noop;

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

    var print = options.beautify
        || options.comments
@@ -276,32 +282,32 @@ function OutputStream(options) {
                space();
            }
        }
-        newline_insert = -1;
        var prev = last.slice(-1);
        if (might_need_semicolon) {
            might_need_semicolon = false;
-
-            if (prev == ":" && ch == "}" || (!ch || ";}".indexOf(ch) < 0) && prev != ";") {
-                if (options.semicolons || requireSemicolonChars[ch]) {
-                    OUTPUT += ";";
+            if (prev == ":" && ch == "}" || prev != ";" && (!ch || ";}".indexOf(ch) < 0)) {
+                var need_semicolon = require_semicolon[ch];
+                if (need_semicolon || options.semicolons) {
+                    output += ";";
                    current_col++;
-                    current_pos++;
+                    if (!line_fixed) {
+                        fix_line();
+                        if (line_fixed && !need_semicolon && output == ";") {
+                            output = "";
+                            current_col = 0;
+                        }
+                    }
+                    if (line_end == output.length - 1) line_end++;
                } else {
                    fix_line();
-                    OUTPUT += "\n";
-                    current_pos++;
+                    output += "\n";
                    current_line++;
                    current_col = 0;
-
-                    if (/^\s+$/.test(str)) {
-                        // reset the semicolon flag, since we didn't print one
-                        // now and might still have to later
-                        might_need_semicolon = true;
-                    }
+                    // reset the semicolon flag, since we didn't print one
+                    // now and might still have to later
+                    if (/^\s+$/.test(str)) might_need_semicolon = true;
                }
-
-                if (!options.beautify)
-                    might_need_space = false;
+                if (!options.beautify) might_need_space = false;
            }
        }

@@ -312,9 +318,8 @@ function OutputStream(options) {
                || str == "--" && last == "!"
                || str == "in" && prev == "/"
                || last == "--" && ch == ">") {
-                OUTPUT += " ";
+                output += " ";
                current_col++;
-                current_pos++;
            }
            if (prev != "<" || str != "!") might_need_space = false;
        }
@@ -324,14 +329,13 @@ function OutputStream(options) {
                token: mapping_token,
                name: mapping_name,
                line: current_line,
-                col: current_col
+                col: current_col,
            });
            mapping_token = false;
            if (line_fixed) flush_mappings();
        }

-        OUTPUT += str;
-        current_pos += str.length;
+        output += str;
        var a = str.split(/\r?\n/), n = a.length - 1;
        current_line += n;
        current_col += a[0].length;
@@ -346,7 +350,7 @@ function OutputStream(options) {
        if (might_need_semicolon) {
            might_need_semicolon = false;
            if (prev == ":" && ch == "}" || (!ch || ";}".indexOf(ch) < 0) && prev != ";") {
-                OUTPUT += ";";
+                output += ";";
                might_need_space = false;
            }
        }
@@ -357,11 +361,11 @@ function OutputStream(options) {
                || str == "--" && last == "!"
                || str == "in" && prev == "/"
                || last == "--" && ch == ">") {
-                OUTPUT += " ";
+                output += " ";
            }
            if (prev != "<" || str != "!") might_need_space = false;
        }
-        OUTPUT += str;
+        output += str;
        last = str;
    };

@@ -373,30 +377,25 @@ function OutputStream(options) {

    var indent = options.beautify ? function(half) {
        if (need_newline_indented) print("\n");
-        print(repeat_string(" ", half ? indentation - (options.indent_level >> 1) : indentation));
+        print(half ? current_indent.slice(0, -half_indent) : current_indent);
    } : noop;

    var with_indent = options.beautify ? function(cont) {
-        var save_indentation = indentation;
-        indentation += options.indent_level;
+        var save_indentation = current_indent;
+        current_indent += full_indent;
        cont();
-        indentation = save_indentation;
+        current_indent = save_indentation;
    } : function(cont) { cont() };

    var may_add_newline = options.max_line_len || options.preserve_line ? function() {
        fix_line();
-        line_end = OUTPUT.length;
+        line_end = output.length;
        line_fixed = false;
    } : noop;

    var newline = options.beautify ? function() {
-        if (newline_insert < 0) return print("\n");
-        if (OUTPUT[newline_insert] != "\n") {
-            OUTPUT = OUTPUT.slice(0, newline_insert) + "\n" + OUTPUT.slice(newline_insert);
-            current_pos++;
-            current_line++;
-        }
-        newline_insert++;
+        print("\n");
+        line_end = output.length;
    } : may_add_newline;

    var semicolon = options.beautify ? function() {
@@ -452,13 +451,12 @@ function OutputStream(options) {
    } : noop;

    function get() {
-        if (!line_fixed) fix_line();
-        return OUTPUT;
+        if (!line_fixed) fix_line(true);
+        return stored + output;
    }

    function has_nlb() {
-        var index = OUTPUT.lastIndexOf("\n");
-        return /^ *$/.test(OUTPUT.slice(index + 1));
+        return /(^|\n) *$/.test(output);
    }

    function pad_comment(token, force) {
@@ -515,15 +513,13 @@ function OutputStream(options) {
            scan.walk(tw);
        }

-        if (current_pos == 0) {
+        if (current_line == 1 && current_col == 0) {
            if (comments.length > 0 && options.shebang && comments[0].type == "comment5") {
                print("#!" + comments.shift().value + "\n");
                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);
@@ -561,20 +557,18 @@ function OutputStream(options) {
            return !/comment[134]/.test(c.type);
        }))) return;
        comments._dumped = self;
-        var insert = OUTPUT.length;
        comments.filter(comment_filter, node).forEach(function(comment, index) {
            pad_comment(comment, index || !tail);
            print_comment(comment);
        });
-        if (OUTPUT.length > insert) newline_insert = insert;
    }

    return {
        get             : get,
        reset           : reset,
        indent          : indent,
-        should_break    : options.width ? function() {
-            return current_col - indentation >= options.width;
+        should_break    : options.beautify && options.width ? function() {
+            return current_col >= options.width;
        } : return_false,
        has_parens      : function() { return last.slice(-1) == "(" },
        newline         : newline,
@@ -790,35 +784,26 @@ function OutputStream(options) {
        if (p instanceof AST_Unary) return true;
    });

-    function lhs_has_optional(node, output) {
-        var p = output.parent();
-        if (p instanceof AST_PropAccess && p.expression === node && is_lhs(p, output.parent(1))) {
-            // ++(foo?.bar).baz
-            // (foo?.()).bar = baz
-            do {
-                if (node.optional) return true;
-                node = node.expression;
-            } while (node.TYPE == "Call" || node instanceof AST_PropAccess);
-        }
+    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) {
-            if (p.expression !== node) return false;
-            // 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";
-        }
-        return lhs_has_optional(node, output);
+        // 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) {
@@ -833,7 +818,10 @@ function OutputStream(options) {
            var g = output.parent(1);
            if (g instanceof AST_Assign && g.left === p) return true;
        }
-        return lhs_has_optional(node, output);
+        // (foo?.())()
+        // (foo?.()).bar
+        // new (foo?.())()
+        return need_chain_parens(node, p);
    });

    PARENS(AST_New, function(output) {
@@ -1158,8 +1146,9 @@ 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);
        }
@@ -1470,7 +1459,7 @@ 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(typeof self.pure == "string" ? "/*" + self.pure + "*/" : "/*@__PURE__*/");
+        output.print("/*@__PURE__*/");
    }
    function print_call_args(self, output) {
        if (self.expression instanceof AST_Call || self.expression instanceof AST_Lambda) {
@@ -1875,8 +1864,8 @@ 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));
--- 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(" ");
@@ -237,15 +237,14 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
        newline_before  : false,
        regex_allowed   : false,
        comments_before : [],
-        directives      : {},
-        directive_stack : [],
+        directives      : Object.create(null),
        read_template   : with_eof_error("Unterminated template literal", function(strings) {
            var s = "";
            for (;;) {
-                var ch = next(true, true);
+                var ch = read();
                switch (ch) {
                  case "\\":
-                    ch += next(true, true);
+                    ch += read();
                    break;
                  case "`":
                    strings.push(s);
@@ -260,6 +259,11 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
                }
                s += ch;
            }
+
+            function read() {
+                var ch = next(true, true);
+                return ch == "\r" ? "\n" : ch;
+            }
        }),
    };
    var prev_was_dot = false;
@@ -630,24 +634,19 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
    };

    next_token.add_directive = function(directive) {
-        S.directive_stack[S.directive_stack.length - 1].push(directive);
-        if (S.directives[directive]) S.directives[directive]++;
-        else S.directives[directive] = 1;
+        S.directives[directive] = true;
    }

    next_token.push_directives_stack = function() {
-        S.directive_stack.push([]);
+        S.directives = Object.create(S.directives);
    }

    next_token.pop_directives_stack = function() {
-        var directives = S.directive_stack.pop();
-        for (var i = directives.length; --i >= 0;) {
-            S.directives[directives[i]]--;
-        }
+        S.directives = Object.getPrototypeOf(S.directives);
    }

    next_token.has_directive = function(directive) {
-        return S.directives[directive] > 0;
+        return !!S.directives[directive];
    }

    return next_token;
@@ -694,6 +693,7 @@ function parse($TEXT, options) {
        expression     : false,
        filename       : null,
        html5_comments : true,
+        module         : false,
        shebang        : true,
        strict         : false,
        toplevel       : null,
@@ -862,6 +862,15 @@ function parse($TEXT, options) {
                    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;
@@ -947,12 +956,6 @@ 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");
@@ -1186,19 +1189,19 @@ function parse($TEXT, options) {
    }

    function for_() {
-        var await = is("name", "await") && next();
+        var await_token = is("name", "await") && next();
        expect("(");
        var init = null;
-        if (await || !is("punc", ";")) {
+        if (await_token || !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))
                : expression(true);
            var ctor;
-            if (await) {
+            if (await_token) {
                expect_token("name", "of");
                ctor = AST_ForAwaitOf;
            } else if (is("operator", "in")) {
@@ -1308,6 +1311,11 @@ 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");
    }

@@ -1327,8 +1335,6 @@ function parse($TEXT, options) {
        var loop = S.in_loop;
        var labels = S.labels;
        ++S.in_function;
-        S.in_directives = true;
-        S.input.push_directives_stack();
        S.in_loop = 0;
        S.labels = [];
        if (is("punc", "{")) {
@@ -1339,8 +1345,6 @@ function parse($TEXT, options) {
            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;
@@ -1354,7 +1358,7 @@ function parse($TEXT, options) {
            value: value,
            end: prev(),
        });
-        if (is_strict) node.each_argname(strict_verify_symbol);
+        if (S.input.has_directive("use strict")) node.each_argname(strict_verify_symbol);
        return node;
    }

@@ -1399,7 +1403,7 @@ function parse($TEXT, options) {
            name: name,
            argnames: argnames,
            rest: argnames.rest || null,
-            body: body
+            body: body,
        });
        if (is_strict) {
            if (name) strict_verify_symbol(name);
@@ -1535,12 +1539,18 @@ function parse($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();
@@ -1555,11 +1565,6 @@ function parse($TEXT, options) {
            if (!is("operator", "*")) return function_(AST_Defun);
            next();
            return function_(AST_GeneratorDefun);
-          case "let":
-            next();
-            var node = let_();
-            semicolon();
-            return node;
          case "var":
            next();
            var node = var_();
@@ -1720,6 +1725,11 @@ function parse($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(),
@@ -1818,10 +1828,7 @@ function parse($TEXT, options) {
        if (is("punc")) {
            switch (start.value) {
              case "`":
-                var tmpl = template(null);
-                tmpl.start = start;
-                tmpl.end = prev();
-                return subscripts(tmpl, allow_calls);
+                return subscripts(template(null), allow_calls);
              case "(":
                next();
                if (is("punc", ")")) {
@@ -2133,7 +2140,7 @@ function parse($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");
    }

@@ -2230,6 +2237,7 @@ 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 = [];
@@ -2240,72 +2248,73 @@ 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, optional) {
+    function subscripts(expr, allow_calls) {
        var start = expr.start;
-        if (is("punc", "[")) {
-            next();
-            var prop = expression();
-            expect("]");
-            return subscripts(new AST_Sub({
-                start: start,
-                optional: optional,
-                expression: expr,
-                property: prop,
-                end: prev(),
-            }), allow_calls);
-        }
-        if (allow_calls && is("punc", "(")) {
-            next();
-            var call = new AST_Call({
-                start: start,
-                optional: optional,
-                expression: expr,
-                args: expr_list(")", !options.strict),
-                end: prev(),
-            });
-            return subscripts(call, true);
-        }
-        if (optional || is("punc", ".")) {
-            if (!optional) next();
-            return subscripts(new AST_Dot({
-                start: start,
-                optional: optional,
-                expression: expr,
-                property: as_name(),
-                end: prev(),
-            }), allow_calls);
-        }
-        if (is("punc", "`")) {
-            var tmpl = template(expr);
-            tmpl.start = expr.start;
-            tmpl.end = prev();
-            return subscripts(tmpl, allow_calls);
-        }
-        if (is("operator", "?") && is_token(peek(), "punc", ".")) {
-            next();
-            next();
-            return subscripts(expr, allow_calls, true);
+        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;
@@ -2532,6 +2541,7 @@ function parse($TEXT, options) {
    return function() {
        var start = S.token;
        var body = [];
+        if (options.module) S.input.add_directive("use strict");
        S.input.push_directives_stack();
        while (!is("eof"))
            body.push(statement());
--- 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",
@@ -72,10 +72,10 @@ var builtins = function() {
            Object.getOwnPropertyNames(ctor.prototype).map(add);
        }
    });
-    return makePredicate(names);
+    return names;

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

@@ -116,9 +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;
@@ -126,7 +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();
@@ -141,8 +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) {
@@ -211,20 +211,20 @@ 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) {
--- 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 = {
@@ -64,19 +64,20 @@ SymbolDef.prototype = {
        this.references.forEach(fn);
    },
    mangle: function(options) {
-        var cache = options.cache && options.cache.props;
-        if (this.global && cache && cache.has(this.name)) {
+        if (this.mangled_name) return;
+        var cache = this.global && options.cache && options.cache.props;
+        if (cache && cache.has(this.name)) {
            this.mangled_name = cache.get(this.name);
-        } else if (!this.mangled_name && !this.unmangleable(options)) {
+        } else if (this.unmangleable(options)) {
+            names_in_use(this.scope, options).set(this.name, true);
+        } else {
            var def = this.redefined();
            if (def) {
                this.mangled_name = def.mangled_name || def.name;
            } else {
                this.mangled_name = next_mangled_name(this, options);
            }
-            if (this.global && cache) {
-                cache.set(this.name, this.mangled_name);
-            }
+            if (cache) cache.set(this.name, this.mangled_name);
        }
    },
    redefined: function() {
@@ -92,18 +93,35 @@ SymbolDef.prototype = {
        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) {
@@ -205,20 +223,17 @@ 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.ie) def.defun = defun.parent_scope.resolve();
+            if (options.ie && node.name != "arguments") 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) {
@@ -231,16 +246,6 @@ 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);
@@ -261,6 +266,7 @@ 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);
            });
@@ -287,6 +293,16 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
                // ensure compression works if `const` reuses a scope variable
                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();
@@ -363,7 +379,7 @@ 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) {
@@ -454,6 +470,7 @@ AST_Lambda.DEFMETHOD("init_vars", function(parent_scope) {
    this.uses_arguments = false;
    this.def_variable(new AST_SymbolFunarg({
        name: "arguments",
+        scope: this,
        start: this.start,
        end: this.end,
    }));
@@ -465,9 +482,12 @@ 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);
            });
        }
@@ -510,12 +530,12 @@ 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);
            }
        });
    }
@@ -526,34 +546,33 @@ 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;
 }

@@ -573,6 +592,7 @@ function _default_mangler_options(options) {
    options = defaults(options, {
        eval        : false,
        ie          : false,
+        keep_fargs  : false,
        keep_fnames : false,
        reserved    : [],
        toplevel    : false,
@@ -580,38 +600,32 @@ 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 = 36;
+    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
-            var save_nesting = lname;
-            descend();
-            if (!options.v8 || !in_label(tw)) lname = save_nesting;
-            return true;
-        }
+        var save_nesting;
        if (node instanceof AST_BlockScope) {
+            // `lname` is incremented when we get to the `AST_Label`
+            if (node instanceof AST_LabeledStatement) save_nesting = lname;
            if (options.webkit && node instanceof AST_IterationStatement && node.init instanceof AST_Let) {
                node.init.definitions.forEach(function(defn) {
                    defn.name.match_symbol(function(sym) {
@@ -627,9 +641,9 @@ 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) {
@@ -640,7 +654,24 @@ 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);
+            if (node instanceof AST_LabeledStatement && !(options.v8 && in_label(tw))) lname = save_nesting;
            return true;
        }
        if (node instanceof AST_Label) {
--- 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
@@ -55,14 +55,6 @@ function find_if(func, array) {
    for (var i = array.length; --i >= 0;) if (func(array[i])) return array[i];
 }

-function repeat_string(str, i) {
-    if (i <= 0) return "";
-    if (i == 1) return str;
-    var d = repeat_string(str, i >> 1);
-    d += d;
-    return i & 1 ? d + str : d;
-}
-
 function configure_error_stack(fn) {
    Object.defineProperty(fn.prototype, "stack", {
        get: function() {
@@ -96,15 +88,6 @@ 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 +126,7 @@ 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 +154,80 @@ 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 +265,21 @@ 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": "3.14.0",
+  "version": "3.16.0",
  "engines": {
    "node": ">=0.8.0"
  },
--- a/test/benchmark.js
+++ b/test/benchmark.js
@@ -17,6 +17,7 @@ var urls = [
    "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/d3/6.7.0/d3.js",
+    "https://cdnjs.cloudflare.com/ajax/libs/antd/4.18.7/antd.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.js
+++ b/test/compress.js
@@ -69,9 +69,7 @@ function make_code(ast, options) {
 function parse_test(file) {
    var script = fs.readFileSync(file, "utf8");
    try {
-        var ast = U.parse(script, {
-            filename: file
-        });
+        var ast = U.parse(script, { filename: file });
    } catch (e) {
        console.error("Caught error while parsing tests in " + file);
        console.error(e);
@@ -98,14 +96,14 @@ function parse_test(file) {
            file: file,
            line: node.start.line,
            col: node.start.col,
-            code: make_code(node, { beautify: false })
+            code: make_code(node, { beautify: false }),
        }));
    }

    function read_string(stat) {
        if (stat.TYPE == "SimpleStatement") {
            var body = stat.body;
-            switch(body.TYPE) {
+            switch (body.TYPE) {
              case "String":
                return body.value;
              case "Array":
@@ -142,7 +140,7 @@ function parse_test(file) {
                ].indexOf(label.name) >= 0, tmpl("Unsupported label {name} [{line},{col}]", {
                    name: label.name,
                    line: label.start.line,
-                    col: label.start.col
+                    col: label.start.col,
                }));
                var stat = node.body;
                if (label.name == "expect_exact" || label.name == "node_version") {
@@ -155,12 +153,12 @@ function parse_test(file) {
                        var ctor = global[body.expression.name];
                        assert.ok(ctor === Error || ctor.prototype instanceof Error, tmpl("Unsupported expect_stdout format [{line},{col}]", {
                            line: label.start.line,
-                            col: label.start.col
+                            col: label.start.col,
                        }));
                        test[label.name] = ctor.apply(null, body.args.map(function(node) {
                            assert.ok(node instanceof U.AST_Constant, tmpl("Unsupported expect_stdout format [{line},{col}]", {
                                line: label.start.line,
-                                col: label.start.col
+                                col: label.start.col,
                            }));
                            return node.value;
                        }));
@@ -183,13 +181,11 @@ function parse_test(file) {
 function reminify(orig_options, input_code, input_formatted, stdout) {
    for (var i = 0; i < minify_options.length; i++) {
        var options = JSON.parse(minify_options[i]);
-        if (options.compress) [
+        [
            "keep_fargs",
            "keep_fnames",
        ].forEach(function(name) {
-            if (name in orig_options) {
-                options.compress[name] = orig_options[name];
-            }
+            if (name in orig_options) options[name] = orig_options[name];
        });
        var options_formatted = JSON.stringify(options, null, 4);
        options.validate = true;
--- a/test/compress/annotations.js
+++ b/test/compress/annotations.js
@@ -442,9 +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/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,
    }
@@ -486,7 +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"
@@ -556,7 +578,7 @@ reduce_iife_3: {
    node_version: ">=4"
 }

-reduce_lambda: {
+reduce_lambda_1: {
    options = {
        evaluate: true,
        reduce_vars: true,
@@ -588,6 +610,43 @@ reduce_lambda: {
    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,
@@ -847,3 +906,203 @@ 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"
+}
+
+issue_5342_1: {
+    options = {
+        dead_code: true,
+        inline: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        for (var a in 0) {
+            (() => {
+                while (1);
+            })(new function(NaN) {
+                a.p;
+            }());
+        }
+        console.log(function() {
+            return b;
+            try {
+                b;
+            } catch (e) {
+                var b;
+            }
+        }());
+    }
+    expect: {
+        for (var a in 0) {
+            (function(NaN) {
+                a.p;
+            })();
+            while (1);
+        }
+        console.log(b);
+        var b;
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}
+
+issue_5342_2: {
+    rename = true
+    options = {
+        dead_code: true,
+        inline: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        for (var a in 0) {
+            (() => {
+                while (1);
+            })(new function(NaN) {
+                a.p;
+            }());
+        }
+        console.log(function() {
+            return b;
+            try {
+                b;
+            } catch (e) {
+                var b;
+            }
+        }());
+    }
+    expect: {
+        for (var a in 0) {
+            a.p;
+            while (1);
+        }
+        console.log(c);
+        var c;
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}
+
+issue_5356: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log((a => a++)(console));
+    }
+    expect: {
+        console.log((a => +a)(console));
+    }
+    expect_stdout: "NaN"
+    node_version: ">=4"
+}
+
+issue_5414_1: {
+    options = {
+        arrows: true,
+        if_return: true,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        (() => {
+            (() => {
+                if (!console)
+                    var arguments = 42;
+                while (console.log(arguments));
+            })();
+        })();
+    }
+    expect: {
+        (() => {
+            if (!console)
+                var arguments = 42;
+            while (console.log(arguments));
+        })();
+    }
+    expect_stdout: true
+    node_version: ">=4"
+}
+
+issue_5414_2: {
+    options = {
+        arrows: true,
+        inline: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        (() => {
+            (() => {
+                if (!console)
+                    var arguments = 42;
+                while (console.log(arguments));
+            })();
+        })();
+    }
+    expect: {
+        (() => {
+            if (!console)
+                var arguments = 42;
+            while (console.log(arguments));
+        })();
+    }
+    expect_stdout: true
+    node_version: ">=4"
+}
+
+issue_5416: {
+    options = {
+        dead_code: true,
+        evaluate: true,
+        inline: true,
+        loops: true,
+        unused: true,
+    }
+    input: {
+        var f = () => {
+            while ((() => {
+                console;
+                var a = function g(arguments) {
+                    console.log(arguments);
+                }();
+            })());
+        };
+        f();
+    }
+    expect: {
+        var f = () => {
+            {
+                arguments = void 0;
+                console;
+                console.log(arguments);
+                var arguments;
+            }
+        };
+        f();
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}
--- a/test/compress/assignments.js
+++ b/test/compress/assignments.js
@@ -489,7 +489,7 @@ logical_assignments: {
    node_version: ">=15"
 }

-logical_collapse_vars: {
+logical_collapse_vars_1: {
    options = {
        collapse_vars: true,
    }
@@ -509,6 +509,46 @@ logical_collapse_vars: {
    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,
@@ -550,6 +590,24 @@ logical_side_effects: {
    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,
@@ -615,8 +673,7 @@ issue_4827_1: {
        c &&= b = a, console.log(b);
    }
    expect: {
-        A = "FAIL";
-        var a = A, b = "PASS", c;
+        var a = A = "FAIL", b = "PASS", c;
        c &&= b = a, console.log(b);
    }
    expect_stdout: "PASS"
--- 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
@@ -427,6 +427,44 @@ negated_if: {
    expect_stdout: "PASS"
 }

+concat_truthy: {
+    options = {
+        booleans: true,
+        evaluate: true,
+    }
+    input: {
+        console.log("foo") + (console.log("bar"), "baz") || console.log("moo");
+    }
+    expect: {
+        console.log("foo") + (console.log("bar"), "baz");
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+    expect_warnings: [
+        "WARN: + in boolean context always true [test/compress/booleans.js:1,8]",
+        "WARN: Condition left of || always true [test/compress/booleans.js:1,8]",
+    ]
+}
+
+process_returns: {
+    options = {
+        booleans: true,
+    }
+    input: {
+        (function() {
+            return 42;
+        })() && console.log("PASS");
+    }
+    expect: {
+        (function() {
+            return 42;
+        })() && console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}
+
 issue_3465_1: {
    options = {
        booleans: true,
@@ -697,3 +735,54 @@ issue_5041_2: {
    }
    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"
+}
+
+issue_5469: {
+    options = {
+        assignments: true,
+        booleans: true,
+        conditionals: true,
+        dead_code: true,
+        evaluate: true,
+        pure_getters: "strict",
+        side_effects: true,
+    }
+    input: {
+        console.log(function f(a) {
+            a && 42[a = A && null];
+        }());
+    }
+    expect: {
+        console.log(function f(a) {
+            a && A,
+            0;
+        }());
+    }
+    expect_stdout: "undefined"
+}
--- a/test/compress/classes.js
+++ b/test/compress/classes.js
@@ -341,7 +341,7 @@ drop_extends: {
    node_version: ">=4"
 }

-keep_extends: {
+keep_extends_1: {
    options = {
        toplevel: true,
        unused: true,
@@ -366,6 +366,43 @@ keep_extends: {
    node_version: ">=4"
 }

+keep_extends_2: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        "use strict";
+        (class extends Function {});
+        console.log("PASS");
+    }
+    expect: {
+        "use strict";
+        (class extends Function {});
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+keep_extends_3: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        class A extends Function {}
+        console.log("PASS");
+    }
+    expect: {
+        "use strict";
+        (class extends Function {});
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 drop_name: {
    options = {
        unused: true,
@@ -434,6 +471,33 @@ static_side_effects: {
        console.log(a);
    }
    expect: {
+        var a = "FAIL 1";
+        (class {
+            static c = a = "PASS";
+        });
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+static_side_effects_strict: {
+    options = {
+        inline: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        var a = "FAIL 1";
+        class A {
+            static p = a = "PASS";
+            q = a = "FAIL 2";
+        }
+        console.log(a);
+    }
+    expect: {
+        "use strict";
        var a = "FAIL 1";
        a = "PASS";
        console.log(a);
@@ -643,6 +707,58 @@ single_use_7: {
    node_version: ">=4"
 }

+single_use_extends: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        class A extends class B {
+            f() {
+                return "PASS";
+            }
+        } {}
+        console.log(new A().f());
+    }
+    expect: {
+        "use strict";
+        console.log(new class extends class {
+            f() {
+                return "PASS";
+            }
+        } {}().f());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+single_use_extends_non_strict: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        class A extends class B {
+            f() {
+                return "PASS";
+            }
+        } {}
+        console.log(new A().f());
+    }
+    expect: {
+        console.log(new class extends class {
+            f() {
+                return "PASS";
+            }
+        } {}().f());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 collapse_non_strict: {
    options = {
        collapse_vars: true,
@@ -715,6 +831,38 @@ collapse_rhs_static: {
    node_version: ">=12"
 }

+inline_non_strict: {
+    options = {
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f(a) {
+            return a.p = "PASS";
+        }
+        class A {
+            g() {
+                return f(42);
+            }
+        }
+        console.log(new A().g());
+    }
+    expect: {
+        function f(a) {
+            return a.p = "PASS";
+        }
+        console.log(new class {
+            g() {
+                return f(42);
+            }
+        }().g());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
 self_comparison: {
    options = {
        booleans: true,
@@ -807,6 +955,33 @@ unused_await: {
        })();
    }
    expect: {
+        var await = "PASS";
+        (async function() {
+            (class {
+                static c = console.log(await);
+            });
+        })();
+    }
+    expect_stdout: true
+    node_version: ">=12 <16"
+}
+
+unused_await_strict: {
+    options = {
+        inline: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        var await = "PASS";
+        (async function() {
+            class A {
+                static p = console.log(await);
+            }
+        })();
+    }
+    expect: {
+        "use strict";
        var await = "PASS";
        (async function() {
            (() => console.log(await))();
@@ -885,12 +1060,14 @@ keep_fnames: {
        class Foo {}
        console.log(Foo.name, class Bar {}.name);
    }
+    expect_stdout: "Foo Bar"
+    node_version: ">=4"
 }

 issue_805_1: {
    options = {
        inline: true,
-        passes: 2,
+        passes: 3,
        pure_getters: "strict",
        reduce_vars: true,
        sequences: true,
@@ -926,7 +1103,7 @@ issue_805_1: {
 issue_805_2: {
    options = {
        inline: true,
-        passes: 2,
+        passes: 3,
        pure_getters: "strict",
        reduce_vars: true,
        sequences: true,
@@ -1149,6 +1326,31 @@ issue_4705: {
        }
    }
    expect: {
+        (class {
+            [console.log("PASS")]() {}
+        });
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+issue_4705_strict: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        var a = "PASS";
+        class A {
+            p = a = "FAIL";
+            [console.log(a)];
+        }
+    }
+    expect: {
+        "use strict";
        console.log("PASS");
    }
    expect_stdout: "PASS"
@@ -1310,6 +1512,7 @@ issue_4725_1: {

 issue_4725_2: {
    options = {
+        if_return: true,
        inline: true,
    }
    input: {
@@ -1370,9 +1573,40 @@ issue_4756: {
    expect: {
        try {
            (class extends 42 {
-                [console.log("foo")]() {}
-            }),
-            (() => console.log("bar"))();
+                static [console.log("foo")] = console.log("bar");
+            });
+        } catch (e) {
+            console.log("baz");
+        }
+    }
+    expect_stdout: [
+        "foo",
+        "baz",
+    ]
+    node_version: ">=12"
+}
+
+issue_4756_strict: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        try {
+            class A extends 42 {
+                static [console.log("foo")] = console.log("bar");
+            }
+        } catch (e) {
+            console.log("baz");
+        }
+    }
+    expect: {
+        "use strict";
+        try {
+            (class extends 42 {
+                static [console.log("foo")] = console.log("bar");
+            });
        } catch (e) {
            console.log("baz");
        }
@@ -1439,7 +1673,7 @@ issue_4829_1: {
    input: {
        "use strict";
        try {
-            class A extends { f(){} }.f {}
+            class A extends { f() {} }.f {}
        } catch (e) {
            console.log("PASS");
        }
@@ -1644,11 +1878,73 @@ issue_4962_1: {
            }
        })(function g() {});
    }
+    expect: {
+        (function() {
+            function f() {
+                while (console.log(typeof g));
+            }
+            (class {
+                static c = f();
+            });
+        })(function g() {});
+    }
+    expect_stdout: "undefined"
+    node_version: ">=12"
+}
+
+issue_4962_1_strict: {
+    options = {
+        ie: true,
+        inline: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        (function() {
+            function f() {
+                while (console.log(typeof g));
+            }
+            class A {
+                static p = f();
+            }
+        })(function g() {});
+    }
+    expect: {
+        "use strict";
+        (function g() {});
+        while (console.log(typeof g));
+    }
+    expect_stdout: "undefined"
+    node_version: ">=12"
+}
+
+issue_4962_1_strict_direct: {
+    options = {
+        ie: true,
+        inline: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function() {
+            function f() {
+                "use strict";
+                while (console.log(typeof g));
+            }
+            class A {
+                static p = f();
+            }
+        })(function g() {});
+    }
    expect: {
        (function g() {}),
-        void function() {
-            while (console.log(typeof g));
-        }();
+        void class {
+            static c = function() {
+                "use strict";
+                while (console.log(typeof g));
+            }();
+        };
    }
    expect_stdout: "undefined"
    node_version: ">=12"
@@ -1672,6 +1968,39 @@ issue_4962_2: {
        }, typeof g));
    }
    expect: {
+        console.log(function f() {}(function g() {
+            function h() {
+                f;
+            }
+            (class {
+                static c = h();
+            });
+        }));
+    }
+    expect_stdout: "undefined"
+    node_version: ">=12"
+}
+
+issue_4962_2_strict: {
+    options = {
+        ie: true,
+        inline: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        console.log(function f() {}(function g() {
+            function h() {
+                f;
+            }
+            class A {
+                static p = h();
+            }
+        }, typeof g));
+    }
+    expect: {
+        "use strict";
        console.log(function f() {}(function g() {
            f;
        }));
@@ -1680,6 +2009,69 @@ issue_4962_2: {
    node_version: ">=12"
 }

+issue_4962_2_strict_direct: {
+    options = {
+        ie: true,
+        inline: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function f() {}(function g() {
+            function h() {
+                "use strict";
+                f;
+            }
+            class A {
+                static p = h();
+            }
+        }, typeof g));
+    }
+    expect: {
+        console.log(function f() {}(function g() {
+            (class {
+                static c = function() {
+                    "use strict";
+                    f;
+                }();
+            });
+        }));
+    }
+    expect_stdout: "undefined"
+    node_version: ">=12"
+}
+
+issue_4962_2_strict_direct_inline: {
+    options = {
+        directives: true,
+        ie: true,
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function f() {}(function g() {
+            function h() {
+                "use strict";
+                f;
+            }
+            class A {
+                static p = h();
+            }
+        }, typeof g));
+    }
+    expect: {
+        console.log(function f() {}(function g() {
+            (class {
+                static c = f;
+            });
+        }));
+    }
+    expect_stdout: "undefined"
+    node_version: ">=12"
+}
+
 issue_4982_1: {
    options = {
        dead_code: true,
@@ -1868,6 +2260,32 @@ issue_5015_3: {
        });
        console.log("PASS");
    }
+    expect: {
+        "use strict";
+        (class A {});
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_5015_4: {
+    options = {
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        (class A {
+            static f() {
+                return A;
+            }
+        });
+        console.log("PASS");
+    }
    expect: {
        "use strict";
        console.log("PASS");
@@ -2027,6 +2445,40 @@ issue_5082_1: {
        })();
    }
    expect: {
+        (function() {
+            class A {
+                p = console.log("PASS");
+                q() {}
+            }
+            (class {
+                static c = new A();
+            });
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+issue_5082_1_strict: {
+    options = {
+        inline: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        (function() {
+            class A {
+                p = console.log("PASS");
+                q() {}
+            }
+            class B {
+                static P = new A();
+            }
+        })();
+    }
+    expect: {
+        "use strict";
        (function() {
            class A {
                p = console.log("PASS");
@@ -2058,6 +2510,41 @@ issue_5082_2: {
        })();
    }
    expect: {
+        (function() {
+            class A {
+                p = console.log("PASS");
+                q() {}
+            }
+            (class {
+                static c = new A();
+            });
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+issue_5082_2_static: {
+    options = {
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        (function() {
+            class A {
+                p = console.log("PASS");
+                q() {}
+            }
+            class B {
+                static P = new A();
+            }
+        })();
+    }
+    expect: {
+        "use strict";
        void new class {
            p = console.log("PASS");
            q() {}
@@ -2066,3 +2553,332 @@ issue_5082_2: {
    expect_stdout: "PASS"
    node_version: ">=12"
 }
+
+issue_5142: {
+    options = {
+        evaluate: true,
+        merge_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 0, b;
+        if (++a)
+            new class {
+                p = b = null;
+                constructor(c) {
+                    console.log(c ? "FAIL" : "PASS");
+                }
+            }(b, a);
+    }
+    expect: {
+        var a = 0, b;
+        if (++a)
+            new class {
+                p = b = null;
+                constructor(c) {
+                    console.log(c ? "FAIL" : "PASS");
+                }
+            }(b, 1);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+issue_5294_1: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        (class A {
+            static p = console.log(typeof A);
+        });
+    }
+    expect: {
+        (class A {
+            static c = console.log(typeof A);
+        });
+    }
+    expect_stdout: "function"
+    node_version: ">=12"
+}
+
+issue_5294_2: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        class A {
+            static p = console.log(typeof A);
+        }
+    }
+    expect: {
+        class A {
+            static p = console.log(typeof A);
+        }
+    }
+    expect_stdout: "function"
+    node_version: ">=12"
+}
+
+issue_5294_3: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = this;
+        (class A {
+            static p = console.log(a === A ? "FAIL" : "PASS");
+        });
+    }
+    expect: {
+        var a = this;
+        (class A {
+            static p = console.log(a === A ? "FAIL" : "PASS");
+        });
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+issue_5294_4: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        (class A {
+            static p = function() {
+                var a = this;
+                console.log(a === A ? "FAIL" : "PASS");
+            }();
+        });
+    }
+    expect: {
+        (class A {
+            static p = function() {
+                console.log(this === A ? "FAIL" : "PASS");
+            }();
+        });
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+issue_5322: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = 41;
+        class A {
+            static p() {
+                console.log(++a);
+            }
+            static q = this.p();
+        }
+    }
+    expect: {
+        var a = 41;
+        (class {
+            static p() {
+                console.log(++a);
+            }
+            static q = this.p();
+        });
+    }
+    expect_stdout: "42"
+    node_version: ">=12"
+}
+
+issue_5352: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        function f(a) {
+            var b;
+            new class {
+                [b = console.log(a)] = b;
+            }(a.p);
+        }
+        f("PASS");
+    }
+    expect: {
+        function f(a) {
+            var b;
+            new class {
+                [b = console.log(a)] = b;
+            }(a.p);
+        }
+        f("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+issue_5387: {
+    options = {
+        properties: true,
+    }
+    input: {
+        "use strict";
+        (function(a) {
+            try {
+                class A extends a {}
+            } catch (e) {
+                console.log("PASS");
+            }
+        })({
+            f() {
+                return this;
+            }
+        }.f);
+    }
+    expect: {
+        "use strict";
+        (function(a) {
+            try {
+                class A extends a {}
+            } catch (e) {
+                console.log("PASS");
+            }
+        })({
+            f() {
+                return this;
+            }
+        }.f);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_5389_1: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+    }
+    input: {
+        function log(m, n) {
+            console.log(m, n);
+        }
+        var a = log;
+        class A {
+            [a = "FAIL"] = a = "PASS";
+        }
+        var b = new A();
+        log(a, b.FAIL);
+    }
+    expect: {
+        function log(m, n) {
+            console.log(m, n);
+        }
+        var a = log;
+        class A {
+            [a = "FAIL"] = a = "PASS";
+        }
+        var b = new A();
+        log(a, b.FAIL);
+    }
+    expect_stdout: "PASS PASS"
+    node_version: ">=12"
+}
+
+issue_5389_2: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+    }
+    input: {
+        function log(m, n) {
+            console.log(m, n);
+        }
+        var a = log;
+        var A = class {
+            [a = "FAIL"] = a = "PASS";
+        };
+        var b = new A();
+        log(a, b.FAIL);
+    }
+    expect: {
+        function log(m, n) {
+            console.log(m, n);
+        }
+        var a = log;
+        var A;
+        var b = new class {
+            [a = "FAIL"] = a = "PASS";
+        }();
+        log(a, b.FAIL);
+    }
+    expect_stdout: "PASS PASS"
+    node_version: ">=12"
+}
+
+issue_5436: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        function f(a) {
+            class A {
+                p = a;
+            }
+            var b = "FAIL";
+            A == b && b();
+            return new A();
+        }
+        console.log(f("PASS").p);
+    }
+    expect: {
+        function f(a) {
+            class A {
+                p = a;
+            }
+            var b = "FAIL";
+            A == b && b();
+            return new A();
+        }
+        console.log(f("PASS").p);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=12"
+}
+
+issue_5481: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        "use strict";
+        var a = "FAIL 1", log = console.log;
+        try {
+            a = "PASS";
+            (class extends 42 {});
+            log("FAIL 2", a);
+        } catch (e) {
+            log(a);
+        }
+    }
+    expect: {
+        "use strict";
+        var a = "FAIL 1", log = console.log;
+        try {
+            a = "PASS";
+            (class extends 42 {});
+            log("FAIL 2", a);
+        } catch (e) {
+            log(a);
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -346,9 +346,7 @@ collapse_vars_if: {
            return "x" != "Bar" + x / 4 ? g9 : g5;
        }
        function f3(x) {
-            if (x)
-                return 1;
-            return 2;
+            return x ? 1 : 2;
        }
    }
 }
@@ -1912,6 +1910,42 @@ collapse_vars_regexp: {
    ]
 }

+collapse_arg_sequence: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a) {
+            a("foo");
+        })((console.log("bar"), console.log));
+    }
+    expect: {
+        (function(a) {
+            (0, console.log)("foo");
+        })(console.log("bar"));
+    }
+    expect_stdout: [
+        "bar",
+        "foo",
+    ]
+}
+
+collapse_for_init: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+    }
+    input: {
+        for (var a = (Math, console), b = a.log("PASS"); b;);
+    }
+    expect: {
+        Math;
+        for (var a, b = console.log("PASS"); b;);
+    }
+    expect_stdout: "PASS"
+}
+
 issue_1537: {
    options = {
        collapse_vars: true,
@@ -2545,7 +2579,7 @@ side_effects_property: {
    expect_stdout: true
 }

-undeclared: {
+undeclared_1: {
    options = {
        collapse_vars: true,
        unused: true,
@@ -2560,8 +2594,68 @@ undeclared: {
    }
    expect: {
        function f(x, y) {
+            return (b = y) + x;
+        }
+    }
+}
+
+undeclared_2: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        function f(x, y) {
+            var a;
+            a = x;
            b = y;
-            return b + x;
+            return a + b;
+        }
+    }
+    expect: {
+        function f(x, y) {
+            return x + (b = y);
+        }
+    }
+}
+
+undeclared_3: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        function f(x, y) {
+            var a;
+            a = x;
+            b = y;
+            return b + a();
+        }
+    }
+    expect: {
+        function f(x, y) {
+            return (b = y) + x();
+        }
+    }
+}
+
+undeclared_4: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        function f(x, y) {
+            var a;
+            a = x;
+            b = y;
+            return a() + b;
+        }
+    }
+    expect: {
+        function f(x, y) {
+            b = y;
+            return x() + b;
        }
    }
 }
@@ -2667,6 +2761,24 @@ chained_4: {
    expect_stdout: "foo undefined"
 }

+chained_5: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = "PASS";
+        var a = (console, console.log(a));
+        a && ++a;
+    }
+    expect: {
+        var a = "PASS";
+        console;
+        var a;
+        (a = console.log(a)) && ++a;
+    }
+    expect_stdout: "PASS"
+}
+
 boolean_binary_1: {
    options = {
        collapse_vars: true,
@@ -2906,6 +3018,127 @@ compound_assignment_2: {
    expect_stdout: "4"
 }

+compound_assignment_3: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = 1;
+        a += (console.log("PASS"), 2);
+        a.p;
+    }
+    expect: {
+        var a = 1;
+        (a += (console.log("PASS"), 2)).p;
+    }
+    expect_stdout: "PASS"
+}
+
+compound_assignment_4: {
+    options = {
+        collapse_vars: true,
+        evaluate: true,
+    }
+    input: {
+        A = "PASS";
+        var a = "";
+        a += (a = "FAIL", A);
+        a.p;
+        console.log(a);
+    }
+    expect: {
+        var a = "";
+        (a += (a = "FAIL", A = "PASS")).p;
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+}
+
+compound_assignment_5: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = 0, b;
+        a += 42;
+        b && (a *= null);
+        console.log(a);
+    }
+    expect: {
+        var a = 0, b;
+        a += 42;
+        b && (a *= null);
+        console.log(a);
+    }
+    expect_stdout: "42"
+}
+
+compound_assignment_6: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a;
+        a ^= 6;
+        a *= a + 1;
+        console.log(a);
+    }
+    expect: {
+        var a;
+        a = (a ^= 6) * (a + 1);
+        console.log(a);
+    }
+    expect_stdout: "42"
+}
+
+compound_assignment_7: {
+    options = {
+        assignments: true,
+        collapse_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = "FA";
+        a = a + "I";
+        a = a + "L";
+        if (console)
+            a = "PASS";
+        console.log(a);
+    }
+    expect: {
+        var a = "FA";
+        a = a + "I" + "L";
+        if (console)
+            a = "PASS";
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+}
+
+compound_assignment_8: {
+    options = {
+        assignments: true,
+        collapse_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 2;
+        a = 3 * a;
+        a = 7 * a;
+        console || (a = "FAIL");
+        console.log(a);
+    }
+    expect: {
+        var a = 2;
+        a = a * 3 * 7;
+        console || (a = "FAIL");
+        console.log(a);
+    }
+    expect_stdout: "42"
+}
+
 issue_2187_1: {
    options = {
        collapse_vars: true,
@@ -3030,10 +3263,10 @@ issue_2203_2: {
            a: "FAIL",
            b: function() {
                return function(c) {
-                    return (String, (Object, function() {
+                    return (Object, function() {
                        return this;
-                    }())).a;
-                }();
+                    }()).a;
+                }(String);
            }
        }.b());
    }
@@ -3731,6 +3964,7 @@ issue_2437_1: {
    options = {
        collapse_vars: true,
        conditionals: true,
+        if_return: true,
        inline: true,
        join_vars: true,
        passes: 2,
@@ -3763,17 +3997,17 @@ issue_2437_1: {
        console.log(foo());
    }
    expect: {
-        console.log(function() {
-            if (xhrDesc) {
-                var result = !!(req = new XMLHttpRequest()).onreadystatechange;
-                return Object.defineProperty(XMLHttpRequest.prototype, "onreadystatechange", xhrDesc || {}),
-                    result;
-            }
-            var req = new XMLHttpRequest(), detectFunc = function(){};
-            return req.onreadystatechange = detectFunc,
-            result = req[SYMBOL_FAKE_ONREADYSTATECHANGE_1] === detectFunc,
-            req.onreadystatechange = null, result;
-        }());
+        var req, detectFunc, result;
+        console.log((
+            xhrDesc ? (result = !!(req = new XMLHttpRequest).onreadystatechange,
+                Object.defineProperty(XMLHttpRequest.prototype, "onreadystatechange", xhrDesc||{})
+            ) : (
+                (req = new XMLHttpRequest).onreadystatechange = detectFunc = function(){},
+                result = req[SYMBOL_FAKE_ONREADYSTATECHANGE_1] === detectFunc,
+                req.onreadystatechange = null
+            ),
+            result
+        ));
    }
 }

@@ -3783,6 +4017,7 @@ issue_2437_2: {
        conditionals: true,
        inline: true,
        join_vars: true,
+        negate_iife: true,
        passes: 3,
        reduce_funcs: true,
        reduce_vars: true,
@@ -3813,15 +4048,15 @@ issue_2437_2: {
        foo();
    }
    expect: {
-        !function() {
-            if (xhrDesc)
-                return (req = new XMLHttpRequest()).onreadystatechange,
-                    Object.defineProperty(XMLHttpRequest.prototype, "onreadystatechange", xhrDesc || {});
-            var req = new XMLHttpRequest();
-            req.onreadystatechange = function(){},
+        var req;
+        xhrDesc ? (
+            (req = new XMLHttpRequest).onreadystatechange,
+            Object.defineProperty(XMLHttpRequest.prototype, "onreadystatechange", xhrDesc || {})
+        ) : (
+            (req = new XMLHttpRequest).onreadystatechange = function(){},
            req[SYMBOL_FAKE_ONREADYSTATECHANGE_1],
-            req.onreadystatechange = null;
-        }();
+            req.onreadystatechange = null
+        );
    }
 }

@@ -6443,7 +6678,8 @@ assign_undeclared: {
        console.log(typeof B);
    }
    expect: {
-        B = new (console.log(42), function() {})();
+        console.log(42);
+        B = new function() {}();
        console.log(typeof B);
    }
    expect_stdout: [
@@ -8156,9 +8392,9 @@ issue_3884_1: {
        console.log(a, b);
    }
    expect: {
-        var a = 100, b = 1;
-        b <<= ++a;
-        console.log(a, b);
+        var a = 100;
+        ++a;
+        console.log(a, 32);
    }
    expect_stdout: "101 32"
 }
@@ -8778,6 +9014,27 @@ collapse_and_assign: {
    expect_stdout: "PASS"
 }

+collapse_and_assign_property: {
+    options = {
+        collapse_vars: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function f() {
+            f && (f.p = "PASS");
+            return f.p;
+        }());
+    }
+    expect: {
+        console.log(function f() {
+            return f.p = f ? "PASS" : f.p;
+        }());
+    }
+    expect_stdout: "PASS"
+}
+
 collapse_or_assign: {
    options = {
        collapse_vars: true,
@@ -8795,7 +9052,7 @@ collapse_or_assign: {
        var a = {
            p: "PASS",
        };
-        log(a = !a.q ? a.p : a);
+        log(a = a.q ? a: a.p);
    }
    expect_stdout: "PASS"
 }
@@ -9139,9 +9396,7 @@ issue_4908: {
        console.log(d[1]);
    }
    expect: {
-        var a = 0, b;
-        console || a++;
-        var c = a, d = [ (d = a) && d, d += 42 ];
+        var a = 0, b, c = (console || a++, a), d = [ (d = a) && d, d += 42 ];
        console.log(d[1]);
    }
    expect_stdout: "42"
@@ -9253,13 +9508,13 @@ issue_4920_2: {
        console.log(b);
    }
    expect: {
-        var o = {
+        var o;
+        var a = "PASS", b;
+        ({
            get PASS() {
                a = "FAIL";
            },
-        };
-        var a = "PASS", b;
-        o[b = a];
+        })[b = a];
        console.log(b);
    }
    expect_stdout: "PASS"
@@ -9283,16 +9538,47 @@ issue_4920_3: {
    }
    expect: {
        var log = console.log;
-        var o = {
+        var o;
+        var a = "PASS", b;
+        ({
            get PASS() {
                a = "FAIL";
            },
+        })[b = a];
+        log(b);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4920_4: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var log = console.log;
+        var o = {
+            get [(a = "FAIL 1", "PASS")]() {
+                a = "FAIL 2";
+            },
+        };
+        var a = "PASS", b;
+        o[b = a];
+        log(b);
+    }
+    expect: {
+        var log = console.log;
+        var o = {
+            get [(a = "FAIL 1", "PASS")]() {
+                a = "FAIL 2";
+            },
        };
        var a = "PASS", b;
        o[b = a];
        log(b);
    }
    expect_stdout: "PASS"
+    node_version: ">=4"
 }

 issue_4935: {
@@ -9343,9 +9629,8 @@ inline_throw: {
    expect: {
        try {
            (function(a) {
-                return function() {
-                    throw a;
-                }();
+                throw a;
+                return;
            })("PASS");
        } catch (e) {
            console.log(e);
@@ -9412,3 +9697,285 @@ issue_4977_2: {
    }
    expect_stdout: "PASS PASS"
 }
+
+issue_5112_1: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        console.log(function(a) {
+            try {
+                try {
+                    if (console + (a = "PASS", ""))
+                        return "FAIL 1";
+                    a.p;
+                } catch (e) {}
+            } finally {
+                return a;
+            }
+        }("FAIL 2"));
+    }
+    expect: {
+        console.log(function(a) {
+            try {
+                try {
+                    if (console + (a = "PASS", ""))
+                        return "FAIL 1";
+                    a.p;
+                } catch (e) {}
+            } finally {
+                return a;
+            }
+        }("FAIL 2"));
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5112_2: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        console.log(function(a) {
+            try {
+                return function() {
+                    try {
+                        if (console + (a = "PASS", ""))
+                            return "FAIL 1";
+                        a.p;
+                    } catch (e) {}
+                }();
+            } finally {
+                return a;
+            }
+        }("FAIL 2"));
+    }
+    expect: {
+        console.log(function(a) {
+            try {
+                return function() {
+                    try {
+                        if (console + (a = "PASS", ""))
+                            return "FAIL 1";
+                        a.p;
+                    } catch (e) {}
+                }();
+            } finally {
+                return a;
+            }
+        }("FAIL 2"));
+    }
+    expect_stdout: "PASS"
+}
+
+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: {
+        var con = console;
+        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: {
+        var con = console;
+        global.log = con.log,
+        console.log((console.log("BAR:", 3), -1), global.log("PASS"));
+    }
+    expect_stdout: [
+        "BAR: 3",
+        "PASS",
+        "-1 undefined",
+    ]
+    node_version: ">=4"
+}
+
+issue_5273: {
+    options = {
+        collapse_vars: true,
+        evaluate: true,
+        inline: true,
+        reduce_vars: true,
+        sequences: true,
+        toplevel: true,
+    }
+    input: {
+        var a = "10", b = 1;
+        function f(c, d) {
+            return d;
+        }
+        f((b += a, b *= a), f);
+        console.log(b);
+    }
+    expect: {
+        var a = "10", b = 1;
+        function f(c, d) {
+            return d;
+        }
+        b = 1100,
+        f,
+        console.log(b);
+    }
+    expect_stdout: "1100"
+}
+
+issue_5276: {
+    options = {
+        collapse_vars: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = A = "PASS";
+        a.p += null;
+        a.p -= 42;
+        console.log(a);
+    }
+    expect: {
+        var a = A = "PASS";
+        a.p = a.p + null - 42;
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5277: {
+    options = {
+        collapse_vars: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var a = function() {
+                a += null;
+                a -= 42;
+            };
+        }());
+    }
+    expect: {
+        console.log(function() {}());
+    }
+    expect_stdout: "undefined"
+}
+
+issue_5309_1: {
+    options = {
+        collapse_vars: true,
+        conditionals: true,
+        toplevel: true,
+    }
+    input: {
+        if (console)
+            var a = (console.log("PASS"), b), b = a;
+        else
+            console.log("FAIL");
+    }
+    expect: {
+        var a, b;
+        console ? (console.log("PASS"), b = b) : console.log("FAIL");
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5309_2: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a, b;
+        console ? (a = (console.log("PASS"), b), b = a) : console.log("FAIL");
+    }
+    expect: {
+        var a, b;
+        console ? (console.log("PASS"), b = b) : console.log("FAIL");
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5394: {
+    options = {
+        collapse_vars: true,
+        evaluate: true,
+    }
+    input: {
+        try {
+            throw A.p = (console.log("FAIL"), []), !1;
+        } catch (e) {
+            console.log(typeof e);
+        }
+    }
+    expect: {
+        try {
+            throw !(A.p = (console.log("FAIL"), []));
+        } catch (e) {
+            console.log(typeof e);
+        }
+    }
+    expect_stdout: "object"
+}
+
+issue_5396: {
+    options = {
+        collapse_vars: true,
+        merge_vars: true,
+        reduce_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a, b;
+        function f() {}
+        b = 0;
+        new function g(c) {
+            var d = a && g(e), e = ++d, i = [ 42 ];
+            for (var j in i)
+                console.log("PASS"),
+                i;
+        }();
+    }
+    expect: {
+        var a, b;
+        function f() {}
+        b = 0;
+        (function g(c) {
+            a && g();
+            for (var j in [ 42 ])
+                console.log("PASS");
+        })();
+    }
+    expect_stdout: "PASS"
+}
--- a/test/compress/comparisons.js
+++ b/test/compress/comparisons.js
@@ -489,7 +489,36 @@ issue_3413: {
    }
    expect: {
        var b;
-        void 0 !== ("" < b || void 0) || console.log("PASS");
+        void 0 === ("" < b || void 0) && console.log("PASS");
    }
    expect_stdout: "PASS"
 }
+
+nullish_assign: {
+    options = {
+        comparisons: true,
+    }
+    input: {
+        var a;
+        void 0 !== (a = "PASS".split("")) && null !== a && console.log(a.join("-"));
+    }
+    expect: {
+        var a;
+        null != (a = "PASS".split("")) && console.log(a.join("-"));
+    }
+    expect_stdout: "P-A-S-S"
+}
+
+nullish_chain: {
+    options = {
+        comparisons: true,
+    }
+    input: {
+        var a;
+        A || B || void 0 === a || null === a || C;
+    }
+    expect: {
+        var a;
+        A || B || null == a || C;
+    }
+}
--- 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
@@ -82,14 +82,14 @@ ifs_3_should_warn: {
        "WARN: Boolean && always false [test/compress/conditionals.js:3,12]",
        "WARN: Condition left of && always false [test/compress/conditionals.js:3,12]",
        "WARN: Condition always false [test/compress/conditionals.js:3,12]",
+        "WARN: Dropping side-effect-free statement [test/compress/conditionals.js:3,12]",
        "WARN: Dropping unreachable code [test/compress/conditionals.js:3,34]",
        "WARN: + in boolean context always true [test/compress/conditionals.js:10,19]",
        "WARN: Boolean || always true [test/compress/conditionals.js:10,12]",
        "WARN: Condition left of || always true [test/compress/conditionals.js:10,12]",
        "WARN: Condition always true [test/compress/conditionals.js:10,12]",
-        "WARN: Dropping unreachable code [test/compress/conditionals.js:12,15]",
-        "WARN: Dropping side-effect-free statement [test/compress/conditionals.js:3,12]",
        "WARN: Dropping side-effect-free statement [test/compress/conditionals.js:10,12]",
+        "WARN: Dropping unreachable code [test/compress/conditionals.js:12,15]",
    ]
 }

@@ -1924,3 +1924,141 @@ 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",
+    ]
+}
+
+issue_5334_1: {
+    options = {
+        conditionals: true,
+        hoist_props: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            if (console.log("PASS"))
+                var o = true, o = {
+                    p: o += console.log("FAIL"),
+                };
+        }
+        f();
+    }
+    expect: {
+        (function() {
+            var o;
+            console.log("PASS") && (o = true, o = {
+                p: o += console.log("FAIL"),
+            });
+        })();
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5334_2: {
+    options = {
+        conditionals: true,
+        hoist_props: true,
+        inline: true,
+        passes: 3,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            if (console.log("PASS"))
+                var o = true, o = {
+                    p: o += console.log("FAIL"),
+                };
+        }
+        f();
+    }
+    expect: {
+        console.log("PASS") && console.log("FAIL");
+    }
+    expect_stdout: "PASS"
+}
--- 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,
@@ -571,8 +597,7 @@ do_if_continue_1: {
    }
    expect: {
        do {
-            if (!console);
-            else {
+            if (console) {
                console.log("PASS");
                {
                    const a = 0;
@@ -602,8 +627,7 @@ do_if_continue_2: {
    }
    expect: {
        do {
-            if (!console);
-            else {
+            if (console) {
                console.log("PASS");
                {
                    const a = 0;
@@ -838,12 +862,10 @@ issue_4202: {
    expect: {
        {
            const o = {};
-            (function() {
-                function f() {
-                    o.p = 42;
-                }
-                f(f);
-            })();
+            function f() {
+                o.p = 42;
+            }
+            f(f);
            console.log(o.p++);
        }
    }
@@ -1219,9 +1241,9 @@ 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 +1281,43 @@ 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,
@@ -1457,6 +1516,7 @@ issue_4689: {

 issue_4691: {
    options = {
+        conditionals: true,
        if_return: true,
        toplevel: true,
    }
@@ -1692,3 +1752,123 @@ issue_4965_2: {
    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"
+}
+
+issue_5319: {
+    options = {
+        collapse_vars: true,
+        merge_vars: true,
+    }
+    input: {
+        (function(a, c) {
+            var b = a, c = b;
+            {
+                const a = c;
+                console.log(c());
+            }
+        })(function() {
+            return "PASS";
+        });
+    }
+    expect: {
+        (function(a, c) {
+            var b = a, c;
+            {
+                const a = c = b;
+                console.log(c());
+            }
+        })(function() {
+            return "PASS";
+        });
+    }
+    expect_stdout: true
+}
+
+issue_5338: {
+    options = {
+        unused: true,
+    }
+    input: {
+        const a = a;
+    }
+    expect: {
+        const a = a;
+    }
+    expect_stdout: true
+}
+
+issue_5476: {
+    mangle = {
+        keep_fargs: true,
+    }
+    input: {
+        console.log(function(n) {
+            const a = 42;
+        }());
+    }
+    expect: {
+        console.log(function(n) {
+            const o = 42;
+        }());
+    }
+    expect_stdout: "undefined"
+}
--- a/test/compress/dead-code.js
+++ b/test/compress/dead-code.js
@@ -1633,3 +1633,39 @@ issue_5030: {
    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
@@ -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,
@@ -568,6 +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,
@@ -1023,7 +1059,7 @@ mangle_arrow_1: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.3"
 }

 mangle_arrow_1_toplevel: {
@@ -1059,7 +1095,7 @@ mangle_arrow_1_toplevel: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.3"
 }

 mangle_arrow_2: {
@@ -1095,7 +1131,7 @@ mangle_arrow_2: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.3"
 }

 mangle_arrow_2_toplevel: {
@@ -1131,7 +1167,7 @@ mangle_arrow_2_toplevel: {
        });
    }
    expect_stdout: "PASS"
-    node_version: ">=6"
+    node_version: ">=6.9.3"
 }

 issue_4444: {
@@ -1573,7 +1609,7 @@ issue_4510_2: {
        };
    }
    expect_stdout: "PASS"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4523: {
@@ -1852,7 +1888,7 @@ issue_5057_2: {

 issue_5057_3: {
    options = {
-        inline: true,
+        inline: 3,
        unused: true,
    }
    input: {
@@ -1875,6 +1911,31 @@ issue_5057_3: {
    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",
@@ -1890,3 +1951,514 @@ issue_5065: {
    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 = {
+        keep_fargs: false,
+        pure_getters: true,
+        unused: true,
+    }
+    input: {
+        console.log(function({} = 42) {
+            return "PASS";
+        }("foo"));
+    }
+    expect: {
+        console.log(function() {
+            return "PASS";
+        }());
+    }
+    expect_stdout: "PASS"
+    expect_warnings: [
+        "INFO: Dropping unused default argument {}=42 [test/compress/default-values.js:1,29]",
+    ]
+    node_version: ">=6"
+}
+
+issue_5246_2: {
+    options = {
+        keep_fargs: false,
+        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,
+        keep_fargs: false,
+        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"
+}
+
+issue_5314_1: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        A = this;
+        new function() {
+            (function(a = console.log(this === A ? "PASS" : "FAIL")) {})();
+        }();
+    }
+    expect: {
+        A = this;
+        (function() {
+            (function(a = console.log(this === A ? "PASS" : "FAIL")) {})();
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5314_2: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        A = this;
+        new function() {
+            ((a = console.log(this === A ? "FAIL" : "PASS")) => {})();
+        }();
+    }
+    expect: {
+        A = this;
+        new function() {
+            console.log(this === A ? "FAIL" : "PASS");
+        }();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5336: {
+    options = {
+        default_values: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        do {
+            (function f(b = console.log("PASS")) {
+                a = f;
+            })(42);
+        } while (a());
+    }
+    expect: {
+        var a;
+        do {
+            (function f(b = console.log("PASS")) {
+                a = f;
+            })(42);
+        } while (a());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5340_1: {
+    options = {
+        keep_fargs: true,
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        var a;
+        (function(b = 42) {})(({ p: a } = true).q);
+        console.log(a);
+    }
+    expect: {
+        var a;
+        (function(b = 0) {})(({ p: a } = true).q);
+        console.log(a);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+issue_5340_2: {
+    options = {
+        keep_fargs: true,
+        pure_getters: "strict",
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        (function(b = 42) {})(({ p: a } = true).q);
+        console.log(a);
+    }
+    expect: {
+        var a;
+        [ [].e = 0 ] = [ ({ p: a } = true).q ];
+        console.log(a);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+issue_5340_3: {
+    options = {
+        keep_fargs: false,
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        var a;
+        (function(b = 42) {})(({ p: a } = true).q);
+        console.log(a);
+    }
+    expect: {
+        var a;
+        (function() {})(a = true["p"]);
+        console.log(a);
+    }
+    expect_stdout: "undefined"
+    node_version: ">=6"
+}
+
+issue_5407: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+    }
+    input: {
+        (function(a) {
+            for (var i = 0; i < 2; i++)
+                (function(b = 4) {
+                    console.log(b);
+                    a = 2;
+                })(a);
+        })();
+    }
+    expect: {
+        (function(a) {
+            for (var i = 0; i < 2; i++)
+                (function(b = 4) {
+                    console.log(b);
+                    a = 2;
+                })(a);
+        })();
+    }
+    expect_stdout: [
+        "4",
+        "2",
+    ]
+    node_version: ">=6"
+}
+
+issue_5444_1: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 42;
+        var b = function({} = setImmediate(function() {
+            console.log(a++);
+        })) {
+            return this;
+        }();
+        console.log(typeof b);
+    }
+    expect: {
+        var a = 42;
+        var b = function({} = setImmediate(function() {
+            console.log(a++);
+        })) {
+            return this;
+        }();
+        console.log(typeof b);
+    }
+    expect_stdout: [
+        "object",
+        "42",
+    ]
+    node_version: ">=6"
+}
+
+issue_5444_2: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        function f(a, b = a++) {
+            return b;
+        }
+        console.log(f("FAIL") || "PASS");
+    }
+    expect: {
+        function f(a, b = a++) {
+            return b;
+        }
+        console.log(f("FAIL") || "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5444_3: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        function f(a, b = function(c = a *= this) {
+            return c;
+        }()) {
+            return b;
+        }
+        console.log(f("FAIL") || "PASS");
+    }
+    expect: {
+        function f(a, b = function(c = a *= this) {
+            return c;
+        }()) {
+            return b;
+        }
+        console.log(f("FAIL") || "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5448_1: {
+    options = {
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a = typeof console.log) {
+            do {
+                var b = [ ...a ];
+            } while (console.log("PASS"));
+        })();
+    }
+    expect: {
+        (function(a = console.log) {
+            do {} while (console.log("PASS"));
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5448_2: {
+    options = {
+        keep_fargs: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(a = typeof console) {
+            do {
+                var b = [ ...a ];
+            } while (console.log("PASS"));
+        })();
+    }
+    expect: {
+        (function(a = 0) {
+            do {} while (console.log("PASS"));
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5448_3: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var [ a = typeof console ] = [ void console.log("PASS") ];
+        var b = [ ...a ];
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5448_4: {
+    options = {
+        evaluate: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var { p: a = typeof console } = { p: void console.log("PASS") };
+        var b = [ ...a ];
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5463: {
+    options = {
+        collapse_vars: true,
+        conditionals: true,
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+    }
+    input: {
+        if (console.log("PASS"))
+            var a = void 0,
+                b = void 0,
+                b = ([ a = FAIL ] = b && b);
+    }
+    expect: {
+        var a, b, b;
+        console.log("PASS") && (
+            b = a = void 0,
+            b = [a = FAIL] = a && a
+        );
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5465: {
+    options = {
+        inline: true,
+        merge_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f(a, b) {
+            (function(c = b = "FAIL 2") {
+                this && console.log(b || "PASS");
+            })(42 - a && a);
+        }
+        f("FAIL 1");
+    }
+    expect: {
+        a = "FAIL 1",
+        void function(c = b = "FAIL 2") {
+            this && console.log(b || "PASS");
+        }(42 - a && a);
+        var a, b;
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5485: {
+    options = {
+        comparisons: true,
+    }
+    input: {
+        (function f(f, a = console.log(void 0 === f ? "PASS" : "FAIL")) {})();
+    }
+    expect: {
+        (function f(f, a = console.log(void 0 === f ? "PASS" : "FAIL")) {})();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
--- 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);
    }
@@ -691,7 +692,7 @@ funarg_inline: {
    node_version: ">=6"
 }

-process_boolean_returns: {
+process_returns: {
    options = {
        booleans: true,
    }
@@ -705,9 +706,7 @@ process_boolean_returns: {
    expect: {
        console.log(function({ length }) {
            return length ? "FAIL" : "PASS";
-        }(function() {
-            return 42;
-        }));
+        }(function() {}));
    }
    expect_stdout: "PASS"
    node_version: ">=6"
@@ -1129,7 +1128,7 @@ drop_unused_2: {
        }
        f();
    }
-    expect:{
+    expect: {
        (function(a) {
            console.log("PASS");
        })();
@@ -1581,6 +1580,75 @@ 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,
@@ -1775,10 +1843,10 @@ issue_4294: {
    expect: {
        A = "PASS";
        (function() {
-            var b = function({
-                [b]: {},
+            var a = function({
+                [a]: {},
            }) {}({
-                [b]: 0,
+                [a]: 0,
            });
            var b = A;
            console.log(b);
@@ -2000,7 +2068,7 @@ issue_4319: {

 issue_4321: {
    options = {
-        inline: true,
+        inline: 3,
        keep_fargs: false,
    }
    input: {
@@ -2127,7 +2195,7 @@ issue_4372_2: {
    }
    expect: {
        var a;
-        [ a ] = [ "PASS", "FAIL" ];
+        [ a ] = a = [ "PASS", "FAIL" ];
        console.log(a);
    }
    expect_stdout: "PASS"
@@ -2952,6 +3020,7 @@ issue_5074_method_pure_getters: {
 issue_5085_1: {
    options = {
        evaluate: true,
+        passes: 2,
        reduce_vars: true,
        toplevel: true,
        unsafe: true,
@@ -2964,8 +3033,7 @@ issue_5085_1: {
    }
    expect: {
        var a = "PASS";
-        var b = [ 42 ][0];
-        b;
+        42;
        console.log(a);
    }
    expect_stdout: "PASS"
@@ -2975,6 +3043,7 @@ issue_5085_1: {
 issue_5085_2: {
    options = {
        evaluate: true,
+        passes: 2,
        reduce_vars: true,
        side_effects: true,
        unsafe: true,
@@ -2991,7 +3060,7 @@ issue_5085_2: {
    expect: {
        var a = "PASS";
        (function(b) {
-            b = [ 42 ][0];
+            0;
        })();
        console.log(a);
    }
@@ -3057,3 +3126,523 @@ issue_5087_2: {
    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_1: {
+    options = {
+        conditionals: true,
+        inline: true,
+        keep_fargs: false,
+        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 (function() {
+            if (console)
+                console.log("PASS");
+        }(), void 0);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5288_2: {
+    options = {
+        conditionals: true,
+        inline: true,
+        keep_fargs: false,
+        passes: 2,
+        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"), void 0);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5314_1: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        A = this;
+        new function() {
+            (function({
+                [console.log(this === A ? "PASS" : "FAIL")]: a,
+            }) {})(42);
+        }();
+    }
+    expect: {
+        A = this;
+        (function() {
+            (function({
+                [console.log(this === A ? "PASS" : "FAIL")]: a,
+            }) {})(42);
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5314_2: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        A = this;
+        new function() {
+            (({
+                [console.log(this === A ? "FAIL" : "PASS")]: a,
+            }) => {})(42);
+        }();
+    }
+    expect: {
+        A = this;
+        new function() {
+            [ {
+                [console.log(this === A ? "FAIL" : "PASS")]: [].e,
+            } ] = [ 42 ];
+        }();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5370: {
+    options = {
+        dead_code: true,
+        ie: true,
+        unused: true,
+    }
+    input: {
+        console.log(function arguments({}) {
+            return arguments;
+            try {} catch (e) {
+                var arguments;
+            }
+        }(42));
+    }
+    expect: {
+        console.log(function arguments({}) {
+            return arguments;
+            var arguments;
+        }(42));
+    }
+    expect_stdout: true
+    node_version: ">=6"
+}
+
+issue_5405_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+    }
+    input: {
+        var [ a ] = [ {} ];
+        console.log(a === a ? "PASS" : "FAIL");
+    }
+    expect: {
+        var [ a ] = [ {} ];
+        console.log(true ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5405_2: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        unsafe: true,
+    }
+    input: {
+        var { p: a } = { p: [] };
+        console.log(a === a ? "PASS" : "FAIL");
+    }
+    expect: {
+        var { p: a } = { p: [] };
+        console.log(true ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5423: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a, b;
+        function f({
+            [function() {
+                if (++a)
+                    return 42;
+            }()]: c
+        }) {}
+        f(b = f);
+        console.log(typeof b);
+    }
+    expect: {
+        var a, b;
+        function f({
+            [function() {
+                if (++a)
+                    return 42;
+            }()]: c
+        }) {}
+        f(b = f);
+        console.log(typeof b);
+    }
+    expect_stdout: "function"
+    node_version: ">=6"
+}
+
+issue_5454: {
+    options = {
+        hoist_props: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f(a) {
+            var a = 42, a = {
+                p: [ a ] = [],
+            };
+            return "PASS";
+        }
+        console.log(f());
+    }
+    expect: {
+        console.log(function(a) {
+            a = 42, a = {
+                p: [ a ] = [],
+            };
+            return "PASS";
+        }());
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5485: {
+    options = {
+        comparisons: true,
+    }
+    input: {
+        (function f({
+            p: f,
+            [console.log(void 0 === f ? "PASS" : "FAIL")]: a,
+        }) {})(42);
+    }
+    expect: {
+        (function f({
+            p: f,
+            [console.log(void 0 === f ? "PASS" : "FAIL")]: a,
+        }) {})(42);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
--- a/test/compress/directives.js
+++ b/test/compress/directives.js
@@ -129,3 +129,32 @@ valid_after_invalid_2: {
    }
    expect_stdout: "undefined"
 }
+
+issue_5368_1: {
+    options = {
+        directives: true,
+        expression: true,
+    }
+    input: {
+        "foo";
+    }
+    expect: {
+        "foo";
+    }
+}
+
+issue_5368_2: {
+    options = {
+        directives: true,
+        expression: true,
+    }
+    input: {
+        "foo";
+        (function() {
+            "bar";
+        })();
+    }
+    expect: {
+        (function() {})();
+    }
+}
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -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,
@@ -2382,7 +2386,8 @@ issue_3664: {
    }
    expect: {
        console.log(function() {
-            var a, b = (a = (a = [ b && console.log("FAIL") ]).p = 0, 0);
+            a = (a = [ b && console.log("FAIL") ]).p = 0;
+            var a, b = 0;
            return "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"
 }
@@ -2652,7 +2656,7 @@ issue_3956: {
        collapse_vars: true,
        evaluate: true,
        inline: true,
-        passes: 2,
+        passes: 3,
        reduce_vars: true,
        sequences: true,
        side_effects: true,
@@ -2783,7 +2787,7 @@ issue_3986: {
    expect_stdout: "0"
 }

-issue_4017: {
+issue_4017_1: {
    options = {
        pure_getters: "strict",
        reduce_vars: true,
@@ -2801,7 +2805,31 @@ issue_4017: {
        var a = 0;
        console.log(function() {
            c &= 0;
-            var c;
+            var c = a++ + (A = a);
+        }());
+    }
+    expect_stdout: "undefined"
+}
+
+issue_4017_2: {
+    options = {
+        passes: 2,
+        pure_getters: "strict",
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        var a = 0;
+        console.log(function f() {
+            var b = c &= 0;
+            var c = a++ + (A = a);
+            var d = c && c[f];
+        }());
+    }
+    expect: {
+        var a = 0;
+        console.log(function() {
+            0;
            a++,
            A = a;
        }());
@@ -2916,7 +2944,7 @@ issue_4133: {
        console.log(a);
    }
    expect: {
-        var b = 1;
+        var a = 1;
        console.log(0);
    }
    expect_stdout: "0"
@@ -3062,7 +3090,7 @@ issue_4184: {
    expect_stdout: "42"
 }

-issue_4235: {
+issue_4235_1: {
    options = {
        inline: true,
        reduce_vars: true,
@@ -3081,13 +3109,37 @@ issue_4235: {
    }
    expect: {
        void function() {
-            var f;
-            console.log(f);
+            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() {
+            {
+                const f = 0;
+            }
+            (function f() {
+                var f = console.log(f);
+            })();
+        })();
+    }
+    expect: {
+        console.log(void 0);
+    }
+    expect_stdout: "undefined"
+}
+
 issue_4404: {
    options = {
        pure_getters: "strict",
@@ -3220,7 +3272,7 @@ issue_4558_1: {
    expect: {
        var a = 0;
        var b = c >>>= a;
-        var c;
+        var c = 0;
        b && a++,
        console.log(a);
    }
@@ -3306,6 +3358,7 @@ issue_4806_1: {
 issue_4806_2: {
    options = {
        sequences: true,
+        side_effects: true,
        toplevel: true,
        unused: true,
    }
@@ -3379,7 +3432,7 @@ issue_4834: {
    }
    expect: {
        try {
-            void b.p;
+            b.p;
        } catch (e) {
            console.log("PASS");
        }
@@ -3492,3 +3545,73 @@ issue_5079: {
    }
    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
@@ -745,7 +745,7 @@ call_args: {
    expect: {
        var a = 1;
        console.log(1);
-        +(1, 1);
+        1, 1;
    }
    expect_stdout: true
 }
@@ -769,7 +769,7 @@ call_args_drop_param: {
    }
    expect: {
        console.log(1);
-        +(b, 1);
+        b, 1;
    }
    expect_stdout: true
 }
@@ -888,6 +888,25 @@ unsafe_charAt_noop: {
    expect_stdout: "f  n"
 }

+chained_side_effects: {
+    options = {
+        evaluate: true,
+    }
+    input: {
+        console.log("foo") || (console.log("bar"), "baz") || console.log("moo");
+    }
+    expect: {
+        console.log("foo") || (console.log("bar"), "baz");
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+    expect_warnings: [
+        "WARN: Condition left of || always true [test/compress/evaluate.js:1,8]",
+    ]
+}
+
 issue_1649: {
    options = {
        evaluate: true,
@@ -2752,8 +2771,7 @@ 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;
        }();
    }
@@ -3203,7 +3221,7 @@ issue_4552: {
    expect_stdout: "NaN"
 }

-issue_4886: {
+issue_4886_1: {
    options = {
        evaluate: true,
        unsafe: true,
@@ -3222,3 +3240,139 @@ issue_4886: {
    }
    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"
+}
+
+issue_5354: {
+    options = {
+        evaluate: true,
+        unsafe: true,
+    }
+    input: {
+        function f(a) {
+            return +a.toExponential(1);
+        }
+        function g(b) {
+            return 0 + b.toFixed(2);
+        }
+        function h(c) {
+            return 1 * c.toPrecision(3);
+        }
+        console.log(typeof f(45), typeof g(67), typeof h(89));
+    }
+    expect: {
+        function f(a) {
+            return +a.toExponential(1);
+        }
+        function g(b) {
+            return 0 + b.toFixed(2);
+        }
+        function h(c) {
+            return +c.toPrecision(3);
+        }
+        console.log(typeof f(45), typeof g(67), typeof h(89));
+    }
+    expect_stdout: "number string number"
+}
+
+issue_5356: {
+    options = {
+        evaluate: true,
+        inline: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            return a++;
+            var a = a;
+        }());
+    }
+    expect: {
+        console.log(+a);
+        var a;
+    }
+    expect_stdout: "NaN"
+}
+
+issue_5362_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = -console;
+        console.log(delete +a);
+    }
+    expect: {
+        var a = -console;
+        console.log((+a, true));
+    }
+    expect_stdout: "true"
+}
+
+issue_5362_2: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        var a = -console;
+        console.log(delete +a);
+    }
+    expect: {
+        console.log(true);
+    }
+    expect_stdout: "true"
+}
+
+issue_5380: {
+    options = {
+        evaluate: true,
+        keep_fnames: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = function f(b) {
+            return function g() {
+                for (b in { PASS: 42 });
+            }(), b;
+        }("FAIL");
+        console.log(a);
+    }
+    expect: {
+        var a = function f(b) {
+            return function g() {
+                for (b in { PASS: 42 });
+            }(), b;
+        }("FAIL");
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+}
--- 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: {
@@ -99,7 +99,7 @@ issue_4664: {
    expect: {
        (function f() {
            new function(a) {
-                console.log(typeof f, 1073741824, typeof this);
+                console.log(typeof f, 2 ** 30, typeof this);
            }(A = 0);
        })();
    }
--- a/test/compress/exports.js
+++ b/test/compress/exports.js
@@ -496,3 +496,16 @@ issue_4766: {
        export var a = "bar";
    }
 }
+
+issue_5444: {
+    options = {
+        unused: true,
+    }
+    input: {
+        export var a = (console, console);
+    }
+    expect: {
+        console;
+        export var a = console;
+    }
+}
--- 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));
@@ -931,7 +934,7 @@ issue_3411: {
    expect: {
        var c = 1;
        !function f() {
-            var o_p = --c && f();
+            var o, o_p = --c && f();
            +{} || console.log("PASS");
        }();
    }
@@ -1042,9 +1045,7 @@ issue_3945_1: {
    expect: {
        function f() {
            o.p;
-            var o = {
-                q: 0,
-            };
+            var o, o_q = 0;
        }
    }
 }
@@ -1063,9 +1064,7 @@ issue_3945_2: {
    }
    expect: {
        console.log(typeof o);
-        var o = {
-            p: 0,
-        };
+        var o, o_p = 0;
    }
    expect_stdout: "undefined"
 }
@@ -1134,10 +1133,73 @@ issue_4985: {
        }());
    }
    expect: {
-        var a_p = 42;
+        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",
+    ]
+}
+
+issue_5441: {
+    options = {
+        hoist_props: true,
+        passes: 2,
+        reduce_vars: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(function(a) {
+            (function() {
+                a = { p: this };
+            })();
+            return typeof a;
+        }());
+    }
+    expect: {
+        console.log(function(a) {
+            (function() {
+                a_p = this;
+            })();
+            var a_p;
+            return typeof {};
+        }());
+    }
+    expect_stdout: "object"
+}
--- a/test/compress/hoist_vars.js
+++ b/test/compress/hoist_vars.js
@@ -135,7 +135,7 @@ issue_2295: {
    }
 }

-issue_4487: {
+issue_4487_1: {
    options = {
        functions: true,
        hoist_vars: true,
@@ -150,16 +150,64 @@ issue_4487: {
        };
        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,
+        keep_fnames: true,
+        passes: 2,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = function f() {
+            var f = console.log(typeof f);
+        };
+        var b = a();
+    }
    expect: {
        function a() {
-            var f;
-            console.log(typeof f);
+            var f = console.log(typeof f);
        }
        a();
    }
    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,
@@ -176,8 +224,7 @@ issue_4489: {
        console.log(k);
    }
    expect: {
-        !(A = 0);
-        for (var k in true);
+        for (var k in !(A = 0));
        console.log(k);
    }
    expect_stdout: "undefined"
@@ -202,8 +249,7 @@ issue_4517: {
    expect: {
        console.log(function() {
            var a = 2;
-            A = a;
-            return A + typeof !1;
+            return (A = a) + typeof !1;
        }());
    }
    expect_stdout: "2boolean"
@@ -234,7 +280,7 @@ issue_4736: {
        (function() {
            (function() {
                0,
-                console.log(1073741824);
+                console.log(1 << 30);
            })();
        })();
    }
@@ -251,18 +297,18 @@ issue_4839: {
        unused: true,
    }
    input: {
-        var o = function(a, b) {
+        var log = console.log, o = function(a, b) {
            return b && b;
        }("foo");
        for (var k in o)
            throw "FAIL";
-        console.log("PASS");
+        log("PASS");
    }
    expect: {
-        var k, o = void 0;
-        for (k in o)
+        var k, log = console.log;
+        for (k in void 0)
            throw "FAIL";
-        console.log("PASS");
+        log("PASS");
    }
    expect_stdout: "PASS"
 }
@@ -288,8 +334,7 @@ issue_4859: {
    }
    expect: {
        (function f(a) {
-            var d = 1 / 0, d = Infinity;
-            console.log(d);
+            console.log(2 + 1 / 0);
            return f;
        })();
    }
@@ -361,9 +406,9 @@ issue_4893_2: {
    expect: {
        try{
            (function() {
-                var b;
-                b = null;
-                b.p += 42;
+                var a;
+                a = null;
+                a.p += 42;
            })();
        } catch (e) {
            console.log("PASS");
@@ -395,3 +440,166 @@ issue_4898: {
    }
    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]"
+}
+
+issue_5378: {
+    options = {
+        hoist_vars: true,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 2;
+        while (a--)
+            (function() {
+                var b;
+                var c;
+                while (console.log(b));
+                --b;
+            })();
+    }
+    expect: {
+        var a = 2;
+        while (a--) {
+            b = void 0;
+            var b, c;
+            while (console.log(b));
+            --b;
+        }
+    }
+    expect_stdout: [
+        "undefined",
+        "undefined",
+    ]
+}
+
+issue_5411_1: {
+    options = {
+        collapse_vars: true,
+        dead_code: true,
+        hoist_vars: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        var a = "PASS";
+        b++;
+        b = a;
+        var b = b, c = c && c[b];
+        console.log(b);
+    }
+    expect: {
+        var b, c, a = "PASS";
+        b++;
+        b = a;
+        c = c && c[b];
+        console.log(b);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5411_2: {
+    options = {
+        collapse_vars: true,
+        dead_code: true,
+        evaluate: true,
+        hoist_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        b++;
+        b = a;
+        var b = b, c = c && c[b];
+        console.log(b);
+    }
+    expect: {
+        var b, c;
+        b++;
+        b = "PASS",
+        c = c && c[b];
+        console.log(b);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5411_3: {
+    options = {
+        collapse_vars: true,
+        hoist_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = console;
+        a++;
+        var a = A = a;
+        console.log(A);
+    }
+    expect: {
+        var a = console;
+        a = A = ++a;
+        console.log(A);
+    }
+    expect_stdout: "NaN"
+}
--- a/test/compress/ie.js
+++ b/test/compress/ie.js
@@ -2631,13 +2631,14 @@ issue_3999: {
    ]
 }

-issue_4001: {
+issue_4001_1: {
    options = {
        collapse_vars: true,
        ie: true,
        inline: true,
        reduce_vars: true,
        sequences: true,
+        side_effects: false,
        toplevel: true,
        unused: true,
    }
@@ -2660,7 +2661,42 @@ issue_4001: {
            return a;
        }
        var a;
-        console.log((a = 42, void f()[42], void function a() {}));
+        console.log((a = 42, f()[42], void f, void function a() {}));
+    }
+    expect_stdout: "undefined"
+}
+
+issue_4001_2: {
+    options = {
+        collapse_vars: true,
+        ie: true,
+        inline: true,
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            function f() {
+                return a;
+                var b;
+            }
+            var c = f();
+            (function g() {
+                c[42];
+                f;
+            })();
+            (function a() {});
+        }(42));
+    }
+    expect: {
+        function f() {
+            return a;
+        }
+        var a;
+        console.log((a = 42, void f()[42]));
    }
    expect_stdout: "undefined"
 }
@@ -3109,9 +3145,9 @@ issue_5081_call: {
        }));
    }
    expect: {
-        function f(b) {
+        function f(a) {
            // IE5-10: TypeError: Function expected
-            return b(b = "A") + (b += "SS");
+            return a(a = "A") + (a += "SS");
        }
        console.log(f(function() {
            return "P";
@@ -3161,8 +3197,8 @@ issue_5081_property_access: {
        console.log(f({ A: "P" }));
    }
    expect: {
-        function f(b) {
-            return b[b = "A"] + (b += "SS");
+        function f(a) {
+            return a[a = "A"] + (a += "SS");
        }
        // IE9-11: undefinedASS
        console.log(f({ A: "P" }));
@@ -3192,3 +3228,249 @@ issue_5081_property_access_ie: {
    }
    expect_stdout: "PASS"
 }
+
+issue_5269_1: {
+    options = {
+        ie: false,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        do {
+            (function() {
+                try {
+                    throw "PASS";
+                } catch (e) {
+                    console.log(e);
+                }
+            })();
+        } while (!console);
+    }
+    expect: {
+        "use strict";
+        do {
+            try {
+                throw "PASS";
+            } catch (e) {
+                console.log(e);
+            }
+        } while (!console);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5269_1_ie: {
+    options = {
+        ie: true,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        "use strict";
+        do {
+            (function() {
+                try {
+                    throw "PASS";
+                } catch (e) {
+                    console.log(e);
+                }
+            })();
+        } while (!console);
+    }
+    expect: {
+        "use strict";
+        do {
+            try {
+                throw "PASS";
+            } catch (e) {
+                console.log(e);
+            }
+        } while (!console);
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5269_2: {
+    options = {
+        ie: false,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        for (var i = 0; i < 2; i++)
+            (function() {
+                console.log(e);
+                try {
+                    console;
+                } catch (e) {
+                    var e = "FAIL 1";
+                }
+                e = "FAIL 2";
+                console;
+            })();
+    }
+    expect: {
+        for (var i = 0; i < 2; i++) {
+            e = void 0;
+            console.log(e);
+            try {
+                console;
+            } catch (e) {
+                var e = "FAIL 1";
+            }
+            e = "FAIL 2";
+            console;
+        }
+    }
+    expect_stdout: [
+        "undefined",
+        "undefined",
+    ]
+}
+
+issue_5269_2_ie: {
+    options = {
+        ie: true,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        for (var i = 0; i < 2; i++)
+            (function() {
+                console.log(e);
+                try {
+                    console;
+                } catch (e) {
+                    var e = "FAIL 1";
+                }
+                e = "FAIL 2";
+                console;
+            })();
+    }
+    expect: {
+        for (var i = 0; i < 2; i++) {
+            e = void 0;
+            console.log(e);
+            try {
+                console;
+            } catch (e) {
+                var e = "FAIL 1";
+            }
+            e = "FAIL 2";
+            console;
+        }
+    }
+    expect_stdout: [
+        "undefined",
+        "undefined",
+    ]
+}
+
+issue_5269_3: {
+    options = {
+        ie: false,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        e = "foo";
+        for (var i = 0; i < 2; i++)
+            (function() {
+                console.log(e);
+                try {
+                    console;
+                } catch (e) {
+                    e = "FAIL";
+                }
+                e = "bar";
+                console;
+            })();
+    }
+    expect: {
+        e = "foo";
+        for (var i = 0; i < 2; i++) {
+            console.log(e);
+            try {
+                console;
+            } catch (e) {
+                e = "FAIL";
+            }
+            e = "bar";
+            console;
+        }
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+}
+
+issue_5269_3_ie: {
+    options = {
+        ie: true,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        e = "foo";
+        for (var i = 0; i < 2; i++)
+            (function() {
+                console.log(e);
+                try {
+                    console;
+                } catch (e) {
+                    e = "FAIL";
+                }
+                e = "bar";
+                console;
+            })();
+    }
+    expect: {
+        e = "foo";
+        for (var i = 0; i < 2; i++) {
+            console.log(e);
+            try {
+                console;
+            } catch (e) {
+                e = "FAIL";
+            }
+            e = "bar";
+            console;
+        }
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+}
+
+issue_5350: {
+    options = {
+        ie: false,
+        properties: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(typeof f, [ 42, function f() {} ][0]);
+    }
+    expect: {
+        console.log(typeof f, 42);
+    }
+    expect_stdout: "undefined 42"
+}
+
+issue_5350_ie: {
+    options = {
+        ie: true,
+        properties: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(typeof f, [ 42, function f() {} ][0]);
+    }
+    expect: {
+        console.log(typeof f, (function f() {}, 42));
+    }
+    expect_stdout: "undefined 42"
+}
--- a/test/compress/if_return.js
+++ b/test/compress/if_return.js
@@ -327,7 +327,7 @@ issue_512: {
    }
 }

-if_var_return: {
+if_var_return_1: {
    options = {
        conditionals: true,
        if_return: true,
@@ -373,6 +373,76 @@ if_var_return: {
    }
 }

+if_var_return_2: {
+    options = {
+        conditionals: true,
+        if_return: true,
+        sequences: true,
+    }
+    input: {
+        (function() {
+            var a = w();
+            if (x())
+                return y();
+            z();
+        })();
+    }
+    expect: {
+        (function() {
+            var a = w();
+            return x() ? y() : (z(), void 0);
+        })();
+    }
+}
+
+if_var_retrn_3: {
+    options = {
+        conditionals: true,
+        if_return: true,
+        sequences: true,
+    }
+    input: {
+        f(function() {
+            var a = w();
+            if (x())
+                return y(a);
+            z();
+        });
+    }
+    expect: {
+        f(function() {
+            var a = w();
+            if (x())
+                return y(a);
+            z();
+        });
+    }
+}
+
+if_var_return_4: {
+    options = {
+        conditionals: true,
+        if_return: true,
+        sequences: true,
+    }
+    input: {
+        function f() {
+            if (u())
+                return v();
+            var a = w();
+            if (x())
+                return y();
+            z();
+        }
+    }
+    expect: {
+        function f() {
+            return u() ? v() : (a = w(), x() ? y() : (z(), void 0));
+            var a;
+        }
+    }
+}
+
 if_if_return_return: {
    options = {
        conditionals: true,
@@ -545,7 +615,36 @@ 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 +665,9 @@ issue_3600: {
    expect: {
        var c = 0;
        (function() {
-            if ([][c++]) b = --b, c = 42;
+            if ([][c++])
+                b = --b,
+                c = 42;
            var b;
        })();
        console.log(c);
@@ -597,7 +698,9 @@ iife_if_return_simple: {

 nested_if_break: {
    options = {
+        conditionals: true,
        if_return: true,
+        side_effects: true,
    }
    input: {
        for (var i = 0; i < 3; i++)
@@ -608,8 +711,7 @@ nested_if_break: {
    }
    expect: {
        for (var i = 0; i < 3; i++)
-            L1: if ("number" == typeof i)
-                if (0 !== i) console.log(i);
+            L1: "number" == typeof i && 0 !== i && console.log(i);
    }
    expect_stdout: [
        "1",
@@ -648,11 +750,11 @@ nested_if_continue: {
        function f(n) {
            for (var i = 0;
                "number" == typeof n
-                    && (0 !== n
-                        ? 1 !== n
-                            ? i++
-                            : console.log("odd", i)
-                        : console.log("even", i)),
+                    && (0 === n
+                        ? console.log("even", i)
+                        : 1 === n
+                        ? console.log("odd", i)
+                        : i++),
                0 <= (n -= 2););
        }
        f(37);
--- a/test/compress/imports.js
+++ b/test/compress/imports.js
@@ -106,6 +106,22 @@ drop_unused: {
    }
 }

+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";
+    }
+}
+
 mangle: {
    rename = false
    mangle = {
--- a/test/compress/indentation.js
+++ b/test/compress/indentation.js
@@ -0,0 +1,100 @@
+numeric: {
+    beautify = {
+        beautify: true,
+        indent_start: 1,
+        indent_level: 3,
+    }
+    input: {
+        switch (42) {
+          case null:
+            console.log("FAIL");
+        }
+        console.log("PASS");
+    }
+    expect_exact: [
+        " switch (42) {",
+        "  case null:",
+        '    console.log("FAIL");',
+        " }",
+        "",
+        ' console.log("PASS");',
+    ]
+    expect_stdout: "PASS"
+}
+
+spaces: {
+    beautify = {
+        beautify: true,
+        indent_start: " ",
+        indent_level: "   ",
+    }
+    input: {
+        switch (42) {
+          case null:
+            console.log("FAIL");
+        }
+        console.log("PASS");
+    }
+    expect_exact: [
+        " switch (42) {",
+        "  case null:",
+        '    console.log("FAIL");',
+        " }",
+        "",
+        ' console.log("PASS");',
+    ]
+    expect_stdout: "PASS"
+}
+
+tabs: {
+    beautify = {
+        beautify: true,
+        indent_start: "\t",
+        indent_level: "\t",
+    }
+    input: {
+        switch (42) {
+          case null:
+            console.log("FAIL");
+        }
+        console.log("PASS");
+    }
+    expect_exact: [
+        "\tswitch (42) {",
+        "\tcase null:",
+        '\t\tconsole.log("FAIL");',
+        "\t}",
+        "",
+        '\tconsole.log("PASS");',
+    ]
+    expect_stdout: "PASS"
+}
+
+mixed: {
+    beautify = {
+        beautify: true,
+        indent_start: "\n",
+        indent_level: "       \t",
+    }
+    input: {
+        switch (42) {
+          case null:
+            console.log("FAIL");
+        }
+        console.log("PASS");
+    }
+    expect_exact: [
+        "",
+        "switch (42) {",
+        "",
+        "    case null:",
+        "",
+        '       \tconsole.log("FAIL");',
+        "",
+        "}",
+        "",
+        "",
+        'console.log("PASS");',
+    ]
+    expect_stdout: "PASS"
+}
--- a/test/compress/issue-1052.js
+++ b/test/compress/issue-1052.js
@@ -4,22 +4,21 @@ multiple_functions: {
        if_return: true,
    }
    input: {
-        ( function() {
-            if ( !window ) {
+        (function() {
+            if (!window)
                return;
-            }
            function f() {}
            function g() {}
-        } )();
+        })();
    }
    expect: {
-        ( function() {
+        (function() {
            // NOTE: other compression steps will reduce this
            // down to just `window`.
-            if ( !window );
+            if (!window);
            function f() {}
            function g() {}
-        } )();
+        })();
    }
 }

@@ -29,18 +28,17 @@ single_function: {
        if_return: true,
    }
    input: {
-        ( function() {
-            if ( !window ) {
+        (function() {
+            if (!window)
                return;
-            }
            function f() {}
-        } )();
+        })();
    }
    expect: {
-        ( function() {
-            if ( !window );
+        (function() {
+            if (!window);
            function f() {}
-        } )();
+        })();
    }
 }

@@ -50,28 +48,26 @@ deeply_nested: {
        if_return: true,
    }
    input: {
-        ( function() {
-            if ( !window ) {
+        (function() {
+            if (!window)
                return;
-            }
            function f() {}
            function g() {}
-            if ( !document ) {
+            if (!document)
                return;
-            }
            function h() {}
-        } )();
+        })();
    }
    expect: {
-        ( function() {
+        (function() {
            // NOTE: other compression steps will reduce this
            // down to just `window`.
-            if ( window )
-                if ( !document );
+            if (!window);
+            else if (!document);
            function f() {}
            function g() {}
            function h() {}
-        } )();
+        })();
    }
 }

@@ -81,18 +77,18 @@ not_hoisted_when_already_nested: {
        if_return: true,
    }
    input: {
-        ( function() {
-            if ( !window ) {
+        (function() {
+            if (!window)
                return;
-            }
-            if ( foo ) function f() {}
-        } )();
+            if (foo) function f() {}
+        })();
    }
    expect: {
-        ( function() {
-            if ( window )
-                if ( foo ) function f() {}
-        } )();
+        (function() {
+            if (!window);
+            else if (foo)
+                function f() {}
+        })();
    }
 }

@@ -104,15 +100,19 @@ defun_if_return: {
    input: {
        function e() {
            function f() {}
-            if (!window) return;
-            else function g() {}
+            if (!window)
+                return;
+            else
+                function g() {}
            function h() {}
        }
    }
    expect: {
        function e() {
            function f() {}
-            if (window) function g() {}
+            if (!window);
+            else
+                function g() {}
            function h() {}
        }
    }
@@ -126,8 +126,10 @@ defun_hoist_funs: {
    input: {
        function e() {
            function f() {}
-            if (!window) return;
-            else function g() {}
+            if (!window)
+                return;
+            else
+                function g() {}
            function h() {}
        }
    }
@@ -136,7 +138,7 @@ defun_hoist_funs: {
            function f() {}
            function g() {}
            function h() {}
-            if (window);
+            if (!window);
        }
    }
 }
@@ -149,15 +151,18 @@ defun_else_if_return: {
    input: {
        function e() {
            function f() {}
-            if (window) function g() {}
-            else return;
+            if (window)
+                function g() {}
+            else
+                return;
            function h() {}
        }
    }
    expect: {
        function e() {
            function f() {}
-            if (window) function g() {}
+            if (window)
+                function g() {}
            function h() {}
        }
    }
--- a/test/compress/issue-1447.js
+++ b/test/compress/issue-1447.js
@@ -40,6 +40,9 @@ conditional_false_stray_else_in_loop: {
            console.log(i);
        }
    }
-    expect_exact: "for(var i=1;i<=4;++i)if(!(i<=2))console.log(i);"
-    expect_stdout: true
+    expect_exact: "for(var i=1;i<=4;++i)if(i<=2);else console.log(i);"
+    expect_stdout: [
+        "3",
+        "4",
+    ]
 }
--- a/test/compress/issue-1704.js
+++ b/test/compress/issue-1704.js
@@ -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";
@@ -366,7 +367,8 @@ 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: {
@@ -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";
@@ -389,7 +392,8 @@ 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: {
@@ -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";
@@ -412,7 +417,8 @@ 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: {
@@ -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-640.js
+++ b/test/compress/issue-640.js
@@ -317,7 +317,35 @@ iife: {
        typeof function g() {}();
    }
    expect: {
-        x = 42, function a() {}(), function b() {}(), function c() {}(),
-        function d() {}(), function e() {}(), function f() {}(), typeof function g() {}();
+        x = 42,
+        function a() {}(),
+        !function b() {}(),
+        ~function c() {}(),
+        +function d() {}(),
+        -function e() {}(),
+        void function f() {}(),
+        typeof function g() {}();
+    }
+}
+
+iife_drop_side_effect_free: {
+    options = {
+        expression: true,
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        x = 42;
+        (function a() {})();
+        !function b() {}();
+        ~function c() {}();
+        +function d() {}();
+        -function e() {}();
+        void function f() {}();
+        typeof function g() {}();
+    }
+    expect: {
+        x = 42,
+        typeof void 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/issue-979.js
+++ b/test/compress/issue-979.js
@@ -1,4 +1,4 @@
-issue979_reported: {
+reported: {
    options = {
        booleans: true,
        comparisons: true,
@@ -17,29 +17,26 @@ issue979_reported: {
    }
    input: {
        function f1() {
-            if (a == 1 || b == 2) {
+            if (a == 1 || b == 2)
                foo();
-            }
        }
        function f2() {
-            if (!(a == 1 || b == 2)) {
-            }
-            else {
+            if (!(a == 1 || b == 2));
+            else
                foo();
-            }
        }
    }
    expect: {
        function f1() {
-            1!=a&&2!=b||foo();
+            1 != a && 2 != b || foo();
        }
        function f2() {
-            1!=a&&2!=b||foo();
+            1 != a && 2 != b || foo();
        }
    }
 }

-issue979_test_negated_is_best: {
+test_negated_is_best: {
    options = {
        booleans: true,
        comparisons: true,
@@ -58,53 +55,47 @@ issue979_test_negated_is_best: {
    }
    input: {
        function f3() {
-            if (a == 1 | b == 2) {
+            if (a == 1 | b == 2)
                foo();
-            }
        }
        function f4() {
-            if (!(a == 1 | b == 2)) {
-            }
-            else {
+            if (!(a == 1 | b == 2));
+            else
                foo();
-            }
        }
        function f5() {
-            if (a == 1 && b == 2) {
+            if (a == 1 && b == 2)
                foo();
-            }
        }
        function f6() {
-            if (!(a == 1 && b == 2)) {
-            }
-            else {
+            if (!(a == 1 && b == 2));
+            else
                foo();
-            }
        }
        function f7() {
-            if (a == 1 || b == 2) {
+            if (a == 1 || b == 2)
                foo();
-            }
-            else {
+            else
                return bar();
-            }
        }
    }
    expect: {
        function f3() {
-            1==a|2==b&&foo();
+            1 == a | 2 == b && foo();
        }
        function f4() {
-            1==a|2==b&&foo();
+            1 == a | 2 == b && foo();
        }
        function f5() {
-            1==a&&2==b&&foo();
+            1 == a && 2 == b && foo();
        }
        function f6() {
-            1!=a||2!=b||foo();
+            1 == a && 2 == b && foo();
        }
        function f7() {
-            if(1!=a&&2!=b)return bar();foo()
+            if (1 != a && 2 != b)
+                return bar();
+            foo();
        }
    }
 }
--- 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,
@@ -990,7 +1144,7 @@ conditional_assignments_3: {
    expect_stdout: "PASS"
 }

-issue_3856: {
+issue_3856_1: {
    options = {
        booleans: true,
        conditionals: true,
@@ -1015,9 +1169,46 @@ issue_3856: {
        console.log(function() {
            (function() {
                var a, b;
-                if (a) return a, 1;
-                for (a = 0; !console;);
-                return 0;
+                if (a) a;
+                else {
+                    a = 0;
+                    for (; !console;);
+                }
+            })();
+        }());
+    }
+    expect_stdout: "undefined"
+}
+
+issue_3856_2: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        if_return: true,
+        join_vars: true,
+        passes: 2,
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(function() {
+            (function() {
+                var a;
+                if (!a) {
+                    a = 0;
+                    for (var b; !console;);
+                    return 0;
+                }
+                if (a) return 1;
+            })();
+        }());
+    }
+    expect: {
+        console.log(function() {
+            (function() {
+                var a, b;
+                if (!a)
+                    for (a = 0; !console;);
            })();
        }());
    }
@@ -1172,10 +1363,7 @@ 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: [
@@ -1183,3 +1371,26 @@ 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
@@ -181,10 +181,10 @@ issue_2203_2: {
            a: "FAIL",
            b: function() {
                return function() {
-                    return (String, (Object, function() {
+                    return (Object, function() {
                        return this;
-                    }())).a;
-                }();
+                    }()).a;
+                }(String);
            }
        }.b());
    }
@@ -925,6 +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,
@@ -1217,6 +1239,7 @@ issues_3267_1: {
        evaluate: true,
        inline: true,
        keep_fargs: false,
+        negate_iife: true,
        reduce_vars: true,
        sequences: true,
        side_effects: true,
--- 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 +20,94 @@ 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,
@@ -182,8 +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",
@@ -192,6 +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,
@@ -792,8 +912,7 @@ do_if_continue_1: {
    expect: {
        "use strict";
        do {
-            if (!console);
-            else {
+            if (console) {
                console.log("PASS");
                {
                    let a = 0;
@@ -826,8 +945,7 @@ do_if_continue_2: {
    expect: {
        "use strict";
        do {
-            if (!console);
-            else {
+            if (console) {
                console.log("FAIL");
                {
                    let a = 0;
@@ -966,12 +1084,10 @@ 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++);
        }
    }
@@ -1488,48 +1604,6 @@ issue_4305_2: {
    node_version: ">=4"
 }

-issue_1753: {
-    mangle = {
-        toplevel: false,
-        webkit: true,
-    }
-    input: {
-        "use strict";
-        let l = null;
-        for (let i = 0; i < 1; i++)
-            console.log(i);
-    }
-    expect: {
-        "use strict";
-        let l = null;
-        for (let i = 0; i < 1; i++)
-            console.log(i);
-    }
-    expect_stdout: "0"
-    node_version: ">=4"
-}
-
-issue_1753_toplevel: {
-    mangle = {
-        toplevel: true,
-        webkit: true,
-    }
-    input: {
-        "use strict";
-        let l = null;
-        for (let i = 0; i < 1; i++)
-            console.log(i);
-    }
-    expect: {
-        "use strict";
-        let l = null;
-        for (let e = 0; e < 1; e++)
-            console.log(e);
-    }
-    expect_stdout: "0"
-    node_version: ">=4"
-}
-
 issue_4438: {
    options = {
        if_return: true,
@@ -1549,11 +1623,9 @@ issue_4438: {
    expect: {
        "use strict";
        function f() {
-            if (!console)
-                ;
-            else {
+            if (console) {
                let a = console.log;
-                a("PASS");
+                void a("PASS");
            }
        }
        f();
@@ -1639,6 +1711,7 @@ issue_4689: {

 issue_4691: {
    options = {
+        conditionals: true,
        if_return: true,
        toplevel: true,
    }
@@ -1747,3 +1820,181 @@ issue_4985: {
    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"
+}
+
+issue_5319: {
+    options = {
+        collapse_vars: true,
+        merge_vars: true,
+    }
+    input: {
+        "use strict";
+        (function(a, c) {
+            var b = a, c = b;
+            {
+                let a = c;
+                console.log(c());
+            }
+        })(function() {
+            return "PASS";
+        });
+    }
+    expect: {
+        "use strict";
+        (function(a, c) {
+            var b = a, c;
+            {
+                let a = c = b;
+                console.log(c());
+            }
+        })(function() {
+            return "PASS";
+        });
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
+issue_5338: {
+    options = {
+        unused: true,
+    }
+    input: {
+        "use strict";
+        let a = a;
+    }
+    expect: {
+        "use strict";
+        a;
+        let a;
+    }
+    expect_stdout: ReferenceError("a is not defined")
+    node_version: ">=4"
+}
+
+issue_5476: {
+    mangle = {
+        keep_fargs: true,
+    }
+    input: {
+        "use strict";
+        console.log(function(n) {
+            let a;
+        }());
+    }
+    expect: {
+        "use strict";
+        console.log(function(n) {
+            let o;
+        }());
+    }
+    expect_stdout: "undefined"
+    node_version: ">=4"
+}
--- a/test/compress/max_line_len.js
+++ b/test/compress/max_line_len.js
@@ -37,6 +37,51 @@ just_enough: {
    expect_warnings: []
 }

+drop_semicolon: {
+    beautify = {
+        max_line_len: 5,
+        semicolons: true,
+    }
+    input: {
+        var a;
+        console.log(a || 42);
+    }
+    expect_exact: [
+        "var a",
+        "console.log(",
+        "a||42",
+        ");",
+    ]
+    expect_stdout: "42"
+    expect_warnings: [
+        "WARN: Output exceeds 5 characters",
+    ]
+}
+
+template_newline: {
+    beautify = {
+        max_line_len: 2,
+    }
+    input: {
+        console.log(`foo
+bar`);
+    }
+    expect_exact: [
+        "console.log(",
+        "`foo",
+        "bar`",
+        ");",
+    ]
+    expect_stdout: [
+        "foo",
+        "bar",
+    ]
+    expect_warnings: [
+        "WARN: Output exceeds 2 characters",
+    ]
+    node_version: ">=4"
+}
+
 issue_304: {
    beautify = {
        max_line_len: 10,
--- a/test/compress/merge_vars.js
+++ b/test/compress/merge_vars.js
--- a/test/compress/negate-iife.js
+++ b/test/compress/negate-iife.js
@@ -122,13 +122,41 @@ negate_iife_4: {
        sequences: true,
    }
    input: {
-        (function(){ return t })() ? console.log(true) : console.log(false);
-        (function(){
+        (function() {
+            return t;
+        })() ? console.log(true) : console.log(false);
+        (function() {
            console.log("something");
        })();
    }
    expect: {
-        !function(){ return t }() ? console.log(false) : console.log(true), function(){
+        !function() {
+            return t;
+        }() ? console.log(false) : console.log(true), !function() {
+            console.log("something");
+        }();
+    }
+}
+
+negate_iife_4_drop_side_effect_free: {
+    options = {
+        conditionals: true,
+        negate_iife: true,
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        (function() {
+            return t;
+        })() ? console.log(true) : console.log(false);
+        (function() {
+            console.log("something");
+        })();
+    }
+    expect: {
+        !function() {
+            return t;
+        }() ? console.log(false) : console.log(true), function() {
            console.log("something");
        }();
    }
@@ -176,17 +204,49 @@ negate_iife_5: {
        sequences: true,
    }
    input: {
-        if ((function(){ return t })()) {
+        if (function() {
+            return t;
+        }()) {
            foo(true);
        } else {
            bar(false);
        }
-        (function(){
+        (function() {
            console.log("something");
        })();
    }
    expect: {
-        !function(){ return t }() ? bar(false) : foo(true), function(){
+        !function() {
+            return t;
+        }() ? bar(false) : foo(true), !function() {
+            console.log("something");
+        }();
+    }
+}
+
+negate_iife_5_drop_side_effect_free: {
+    options = {
+        conditionals: true,
+        negate_iife: true,
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        if (function() {
+            return t;
+        }()) {
+            foo(true);
+        } else {
+            bar(false);
+        }
+        (function() {
+            console.log("something");
+        })();
+    }
+    expect: {
+        !function() {
+            return t;
+        }() ? bar(false) : foo(true), function() {
            console.log("something");
        }();
    }
@@ -389,6 +449,7 @@ issue_1288_side_effects: {
    options = {
        conditionals: true,
        negate_iife: true,
+        sequences: true,
        side_effects: true,
    }
    input: {
@@ -409,10 +470,10 @@ issue_1288_side_effects: {
            })(0);
    }
    expect: {
-        w;
+        w,
        x || function() {
            x = {};
-        }();
+        }(),
        y;
    }
 }
--- a/test/compress/nullish.js
+++ b/test/compress/nullish.js
@@ -262,6 +262,30 @@ de_morgan_2e: {
    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,
@@ -280,3 +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
@@ -842,9 +842,9 @@ unary_binary_parentheses: {
        v.forEach(function(x) {
            v.forEach(function(y) {
                console.log(
-                    +x*y,
-                    +x/y,
-                    +x%y,
+                    x*y,
+                    x/y,
+                    x%y,
                    -x*y,
                    -x/y,
                    -x%y
@@ -1397,7 +1397,7 @@ issue_3695: {
    }
    expect: {
        var a = [];
-        console.log(+(a * (a[0] = false)));
+        console.log(a * (a[0] = false));
    }
    expect_stdout: "NaN"
 }
--- 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
@@ -58,7 +58,7 @@ assign_parentheses_dot: {
    input: {
        (console?.log).name.p = console.log("PASS");
    }
-    expect_exact: '(console?.log.name).p=console.log("PASS");'
+    expect_exact: '(console?.log).name.p=console.log("PASS");'
    expect_stdout: "PASS"
    node_version: ">=14"
 }
@@ -72,6 +72,26 @@ assign_no_parentheses: {
    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 };
@@ -237,6 +257,99 @@ trim_2: {
    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,
@@ -248,7 +361,9 @@ issue_4906: {
        } while (console.log("PASS"));
    }
    expect: {
-        do {} while (console.log("PASS"));
+        do {
+            var a = a?.[42];
+        } while (console.log("PASS"));
    }
    expect_stdout: "PASS"
    node_version: ">=14"
@@ -321,7 +436,7 @@ issue_5039: {
        console.log("PASS");
    }
    expect: {
-        (function f() {});
+        var a = a?.[function f() {}];
        console.log("PASS");
    }
    expect_stdout: "PASS"
@@ -342,14 +457,163 @@ issue_5091: {
        console.log(f("FAIL 1") || "PASS");
    }
    expect: {
-        function f(b) {
-            var b = b.p;
+        function f(a) {
+            var a = a.p;
            var c;
-            b?.[c = "FAIL 2"];
-            return b || 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/preserve_line.js
+++ b/test/compress/preserve_line.js
@@ -97,10 +97,10 @@ return_5: {
    }
    expect_exact: [
        "_is_selected=function(tags,slug){",
-        "var ref",
+        "var ref;",
        "",
        "",
-        ";return null!=(ref=_.find(tags,{slug:slug}))?ref.selected:void 0};",
+        "return null!=(ref=_.find(tags,{slug:slug}))?ref.selected:void 0};",
    ]
 }

@@ -146,10 +146,10 @@ return_7: {
    }
    expect_exact: [
        "_is_selected=function(e,l){",
-        "var n",
+        "var n;",
        "",
        "",
-        ";return null!=(n=_.find(e,{slug:l}))?n.selected:void 0};",
+        "return null!=(n=_.find(e,{slug:l}))?n.selected:void 0};",
    ]
 }

--- a/test/compress/properties.js
+++ b/test/compress/properties.js
@@ -1510,3 +1510,71 @@ issue_5093_quote_style: {
    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_getters.js
+++ b/test/compress/pure_getters.js
@@ -1289,6 +1289,7 @@ issue_2878: {
        collapse_vars: true,
        pure_getters: true,
        sequences: true,
+        side_effects: true,
    }
    input: {
        var c = 0;
@@ -1363,9 +1364,8 @@ 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"
@@ -1640,6 +1640,26 @@ nested_property_assignments_3: {
    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",
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -6,6 +6,7 @@ reduce_vars: {
            C: 0,
        },
        inline: true,
+        passes: 2,
        reduce_funcs: true,
        reduce_vars: true,
        toplevel: true,
@@ -41,10 +42,8 @@ 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 +904,7 @@ use_before_var: {
    }
    expect: {
        function f(){
-            console.log(void 0);
+            console.log(t);
            var t = 1;
        }
    }
@@ -981,7 +980,7 @@ 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);
@@ -6671,6 +6670,7 @@ issues_3267_1: {
        dead_code: true,
        evaluate: true,
        inline: true,
+        negate_iife: true,
        reduce_vars: true,
        sequences: true,
        side_effects: true,
@@ -6688,7 +6688,7 @@ issues_3267_1: {
        });
    }
    expect: {
-        !function(i) {
+        !function(x) {
            if (Object())
                return console.log("PASS");
            throw "FAIL";
@@ -6705,6 +6705,7 @@ issues_3267_2: {
        evaluate: true,
        inline: true,
        keep_fargs: false,
+        negate_iife: true,
        passes: 2,
        reduce_vars: true,
        sequences: true,
@@ -7320,6 +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,
@@ -7435,6 +7494,7 @@ issue_4030: {
        collapse_vars: true,
        evaluate: true,
        reduce_vars: true,
+        side_effects: true,
        toplevel: true,
        unused: true,
    }
@@ -7772,3 +7832,67 @@ issue_5055_2: {
    }
    expect_stdout: "PASS"
 }
+
+issue_5324: {
+    options = {
+        inline: true,
+        merge_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        A = 0;
+        do {
+            var a, b = A;
+            for (a in b)
+                var c = b;
+        } while (function() {
+            var d;
+            console.log(d *= A);
+        }());
+    }
+    expect: {
+        A = 0;
+        do {
+            var a, b = A;
+            for (a in b);
+        } while (b = void 0, void console.log(b *= A));
+    }
+    expect_stdout: "NaN"
+}
+
+issue_5434: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            for (var i = 0; i < 2; i++) {
+                var b = "FAIL";
+                f && f();
+                a = b;
+                var f = function() {
+                    b = "PASS";
+                };
+            }
+            return a;
+        }());
+    }
+    expect: {
+        console.log(function(a) {
+            for (var i = 0; i < 2; i++) {
+                var b = "FAIL";
+                f && f();
+                a = b;
+                var f = function() {
+                    b = "PASS";
+                };
+            }
+            return a;
+        }());
+    }
+    expect_stdout: "PASS"
+}
--- 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: {
@@ -270,7 +270,7 @@ retain_destructured_object_1: {
        "1 PASS",
        "2 42",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 retain_destructured_object_2: {
@@ -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: {
@@ -344,11 +344,12 @@ 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: {
    options = {
+        keep_fargs: false,
        unused: true,
    }
    input: {
@@ -359,10 +360,10 @@ 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: {
@@ -436,9 +437,9 @@ merge_funarg: {
        })();
    }
    expect: {
-        (function(...b) {
-            var b = b.length;
-            console.log(b);
+        (function(...a) {
+            var a = a.length;
+            console.log(a);
        })();
    }
    expect_stdout: "0"
@@ -456,9 +457,9 @@ 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"
@@ -476,13 +477,13 @@ 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: {
@@ -636,6 +637,24 @@ keep_rest_lambda_2: {
    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,
@@ -848,9 +867,9 @@ issue_4575: {
    }
    expect: {
        (function(a) {
-            (function a(...d) {
+            (function(d) {
                console.log(d.length);
-            })();
+            })([]);
        })();
    }
    expect_stdout: "0"
@@ -974,7 +993,7 @@ issue_5089_1: {
        console.log(o.p);
    }
    expect_stdout: "undefined"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_5089_2: {
@@ -1001,5 +1020,346 @@ issue_5089_2: {
        console.log(o.p);
    }
    expect_stdout: "undefined"
-    node_version: ">=8"
+    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: {
+                q: a,
+            } = 42,
+            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"), {
+                q: a,
+            } = 42),
+        } ][0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=10.22.0"
+}
+
+issue_5108: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        rests: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        console.log(function([ ...[ a ] ]) {
+            return a;
+        }([ "PASS", "FAIL" ]));
+    }
+    expect: {
+        console.log("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 = {
+        keep_fargs: false,
+        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 = {
+        keep_fargs: false,
+        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 = {
+        keep_fargs: false,
+        unused: true,
+    }
+    input: {
+        (function f(...[ [ a ] ]) {
+            console.log(a);
+        })([ "PASS" ]);
+    }
+    expect: {
+        (function(...[ a ]) {
+            console.log(a);
+        })([ "PASS" ][0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_5360: {
+    options = {
+        keep_fargs: false,
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        var a;
+        console.log(function({ p: {}, ...b }) {
+            return b.q;
+        }({
+            p: ~a && ([ a ] = []),
+            q: "PASS",
+        }));
+    }
+    expect: {
+        var a;
+        console.log(function({ p: {}, ...b }) {
+            return b.q;
+        }({
+            p: ~a && ([ a ] = []),
+            q: "PASS",
+        }));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8.3.0"
+}
+
+issue_5370: {
+    options = {
+        dead_code: true,
+        ie: true,
+        unused: true,
+    }
+    input: {
+        console.log(function arguments(...a) {
+            return arguments;
+            try {} catch (e) {
+                var arguments;
+            }
+        }());
+    }
+    expect: {
+        console.log(function arguments(...a) {
+            return arguments;
+            var arguments;
+        }());
+    }
+    expect_stdout: true
+    node_version: ">=6"
+}
+
+issue_5391: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        objects: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a, b = function f({
+            p: {},
+            ...c
+        }) {
+            while (c.q);
+        }({
+            p: {
+                r: a++,
+                r: 0,
+            }
+        });
+        console.log(a);
+    }
+    expect: {
+        (function({
+            p: {},
+            ...c
+        }) {
+            while (c.q);
+        })({
+            p: 0,
+        });
+        console.log(NaN);
+    }
+    expect_stdout: "NaN"
+    node_version: ">=8.3.0"
 }
--- a/test/compress/sandbox.js
+++ b/test/compress/sandbox.js
@@ -201,3 +201,20 @@ issue_4811_2: {
    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
@@ -289,8 +289,34 @@ iife: {
        typeof function g() {}();
    }
    expect: {
-        x = 42, function a() {}(), function b() {}(), function c() {}(),
-        function d() {}(), function e() {}(), function f() {}(), function g() {}();
+        x = 42,
+        function a() {}(),
+        !function b() {}(),
+        ~function c() {}(),
+        +function d() {}(),
+        -function e() {}(),
+        void function f() {}(),
+        typeof function g() {}();
+    }
+}
+
+iife_drop_side_effect_free: {
+    options = {
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        x = 42;
+        (function a() {})();
+        !function b() {}();
+        ~function c() {}();
+        +function d() {}();
+        -function e() {}();
+        void function f() {}();
+        typeof function g() {}();
+    }
+    expect: {
+        x = 42;
    }
 }

@@ -774,7 +800,7 @@ 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 +936,7 @@ hoist_decl: {
        var d;
    }
    expect: {
-        var a;
-        w();
-        var b = x(), c, d;
+        var a, b = (w(), x()), c, d;
        for (y(); 0;) z();
    }
 }
@@ -1047,11 +1071,102 @@ call: {
        b.c = function() {
            console.log(this === b ? "bar" : "baz");
        },
+        a,
        b(),
+        a,
        b.c(),
        (a, b.c)(),
+        a,
        b["c"](),
        (a, b["c"])(),
+        a,
+        function() {
+            console.log(this === a);
+        }(),
+        a,
+        new b(),
+        a,
+        new b.c(),
+        a,
+        new b.c(),
+        a,
+        new b["c"](),
+        a,
+        new b["c"](),
+        a,
+        new function() {
+            console.log(this === a);
+        }(),
+        console.log((a, typeof b.c)),
+        console.log((a, typeof b["c"]));
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+        "baz",
+        "bar",
+        "baz",
+        "true",
+        "foo",
+        "baz",
+        "baz",
+        "baz",
+        "baz",
+        "false",
+        "function",
+        "function",
+    ]
+}
+
+call_drop_side_effect_free: {
+    options = {
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        var a = function() {
+            return this;
+        }();
+        function b() {
+            console.log("foo");
+        }
+        b.c = function() {
+            console.log(this === b ? "bar" : "baz");
+        };
+        (a, b)();
+        (a, b).c();
+        (a, b.c)();
+        (a, b)["c"]();
+        (a, b["c"])();
+        (a, function() {
+            console.log(this === a);
+        })();
+        new (a, b)();
+        new (a, b).c();
+        new (a, b.c)();
+        new (a, b)["c"]();
+        new (a, b["c"])();
+        new (a, function() {
+            console.log(this === a);
+        })();
+        console.log(typeof (a, b).c);
+        console.log(typeof (a, b)["c"]);
+    }
+    expect: {
+        var a = function() {
+            return this;
+        }();
+        function b() {
+            console.log("foo");
+        }
+        b.c = function() {
+            console.log(this === b ? "bar" : "baz");
+        },
+        b(),
+        b.c(),
+        (0, b.c)(),
+        b["c"](),
+        (0, b["c"])(),
        function() {
            console.log(this === a);
        }(),
@@ -1063,8 +1178,8 @@ call: {
        new function() {
            console.log(this === a);
        }(),
-        console.log((a, typeof b.c)),
-        console.log((a, typeof b["c"]));
+        console.log(typeof b.c),
+        console.log(typeof b["c"]);
    }
    expect_stdout: [
        "foo",
@@ -1099,6 +1214,26 @@ missing_link: {
    expect: {
        var a = 100;
        a,
+        a++ + (0, 1),
+        console.log(a);
+    }
+}
+
+missing_link_drop_side_effect_free: {
+    options = {
+        conditionals: true,
+        evaluate: true,
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        var a = 100;
+        a;
+        a++ + (0 ? 2 : 1);
+        console.log(a);
+    }
+    expect: {
+        var a = 100;
        a++,
        console.log(a);
    }
@@ -1162,10 +1297,8 @@ 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 +1328,8 @@ issue_3490_2: {
    }
    expect: {
        var b = 42, c = "FAIL";
-        for (function() {
-            var a;
-        }(), c = "PASS", b; "" == typeof d;);
+        var a;
+        for (c = "PASS"; "" == typeof d;);
        console.log(c, b);
    }
    expect_stdout: "PASS 42"
--- a/test/compress/side_effects.js
+++ b/test/compress/side_effects.js
@@ -617,7 +617,7 @@ issue_4730_2: {
    }
    expect: {
        var a;
-        !console.log("PASS") || a && a[a.p];
+        console.log("PASS") && a && a[a.p];
    }
    expect_stdout: "PASS"
 }
--- 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: {
@@ -994,7 +1056,7 @@ issue_4849: {
        }()));
    }
    expect_stdout: "object"
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4882_1: {
@@ -1026,7 +1088,7 @@ issue_4882_1: {
        "PASS",
        "undefined",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4882_2: {
@@ -1052,7 +1114,7 @@ issue_4882_2: {
        "42",
        "PASS",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_4882_3: {
@@ -1082,7 +1144,7 @@ issue_4882_3: {
        "PASS",
        "42",
    ]
-    node_version: ">=8"
+    node_version: ">=8.3.0"
 }

 issue_5006: {
@@ -1104,3 +1166,31 @@ issue_5006: {
    expect_stdout: "PASS"
    node_version: ">=6"
 }
+
+issue_5382: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        ({
+            f() {
+                ({ ...this });
+            },
+            get p() {
+                console.log("PASS");
+            },
+        }).f();
+    }
+    expect: {
+        ({
+            f() {
+                ({ ...this });
+            },
+            get p() {
+                console.log("PASS");
+            },
+        }).f();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8.3.0"
+}
--- a/test/compress/templates.js
+++ b/test/compress/templates.js
@@ -131,6 +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: [
+        "",
+        "${",
+        "",
+    ]
+    node_version: ">=4"
+}
+
 evaluate: {
    options = {
        evaluate: true,
@@ -174,7 +273,7 @@ partial_evaluate: {
        console.log(`${6 * 7} foo ${console ? `PA` + "SS" : `FA` + `IL`}`);
    }
    expect: {
-        console.log(`42 foo ${console ? "PASS" : "FAIL"}`);
+        console.log("42 foo " + (console ? "PASS" : "FAIL"));
    }
    expect_stdout: "42 foo PASS"
    node_version: ">=4"
@@ -204,7 +303,7 @@ malformed_evaluate_2: {
        console.log(`\u0${0}b${5}`);
    }
    expect: {
-        console.log(`\u0${0}b5`);
+        console.log(`\u00b` + 5);
    }
    expect_stdout: true
    node_version: ">=4"
@@ -238,7 +337,7 @@ malformed_evaluate_4: {
        console.log("\\u00b5");
    }
    expect_stdout: "\\u00b5"
-    node_version: ">=8"
+    node_version: ">=8.10.0"
 }

 unsafe_evaluate: {
@@ -254,7 +353,7 @@ unsafe_evaluate: {
        console.log("\\uFo");
    }
    expect_stdout: "\\uFo"
-    node_version: ">=8"
+    node_version: ">=8.10.0"
 }

 side_effects_1: {
@@ -357,13 +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"
@@ -434,3 +534,238 @@ issue_4931: {
    ]
    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/typeof.js
+++ b/test/compress/typeof.js
@@ -307,7 +307,7 @@ typeof_defined_1: {
    }
    expect: {
        "undefined" == typeof A && A;
-        "undefined" != typeof A || A;
+        "undefined" == typeof A && A;
    }
 }

@@ -324,7 +324,7 @@ typeof_defined_2: {
    }
    expect: {
        "function" != typeof A && A;
-        "function" == typeof A || A;
+        "function" != typeof A && A;
    }
 }

@@ -355,16 +355,19 @@ typeof_defined_3: {
        "undefined" == typeof A && "undefined" == typeof B && (A, B);
        "undefined" == typeof A && "undefined" != typeof B && A;
        "undefined" != typeof A && "undefined" == typeof B && B;
+        // dropped
        "undefined" == typeof A && "undefined" == typeof B || (A, B);
        "undefined" == typeof A && "undefined" != typeof B || (A, B);
        "undefined" != typeof A && "undefined" == typeof B || (A, B);
        "undefined" != typeof A && "undefined" != typeof B || (A, B);
-        "undefined" == typeof A || "undefined" == typeof B && B;
-        "undefined" != typeof A || "undefined" == typeof B && (A, B);
-        "undefined" != typeof A || "undefined" != typeof B && A;
-        "undefined" == typeof A || "undefined" != typeof B || B;
-        "undefined" != typeof A || "undefined" == typeof B || A;
-        "undefined" != typeof A || "undefined" != typeof B || (A, B);
+        "undefined" != typeof A && "undefined" == typeof B && B;
+        // dropped
+        "undefined" == typeof A && "undefined" == typeof B && (A, B);
+        "undefined" == typeof A && "undefined" != typeof B && A;
+        // dropped
+        "undefined" != typeof A && "undefined" == typeof B && B;
+        "undefined" == typeof A && "undefined" != typeof B && A;
+        "undefined" == typeof A && "undefined" == typeof B && (A, B);
    }
 }

@@ -392,6 +395,7 @@ typeof_defined_4: {
        "object" != typeof A || "object" != typeof B || (A, B);
    }
    expect: {
+        // dropped
        "object" == typeof A && "object" != typeof B && B;
        "object" != typeof A && "object" == typeof B && A;
        "object" != typeof A && "object" != typeof B && (A, B);
@@ -399,12 +403,14 @@ typeof_defined_4: {
        "object" == typeof A && "object" != typeof B || (A, B);
        "object" != typeof A && "object" == typeof B || (A, B);
        "object" != typeof A && "object" != typeof B || (A, B);
-        "object" == typeof A || "object" == typeof B && A;
-        "object" == typeof A || "object" != typeof B && (A, B);
-        "object" != typeof A || "object" != typeof B && B;
-        "object" == typeof A || "object" == typeof B || (A, B);
-        "object" == typeof A || "object" != typeof B || A;
-        "object" != typeof A || "object" == typeof B || B;
+        "object" != typeof A && "object" == typeof B && A;
+        "object" != typeof A && "object" != typeof B && (A, B);
+        // dropped
+        "object" == typeof A && "object" != typeof B && B;
+        "object" != typeof A && "object" != typeof B && (A, B);
+        "object" != typeof A && "object" == typeof B && A;
+        "object" == typeof A && "object" != typeof B && B;
+        // dropped
    }
 }

@@ -436,6 +442,245 @@ 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, 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"
--- a/test/compress/webkit.js
+++ b/test/compress/webkit.js
@@ -107,3 +107,209 @@ function_name_mangle_ie8: {
    expect_exact: "(function(){console.log(typeof function n(o){})})();"
    expect_stdout: "function"
 }
+
+issue_1753: {
+    mangle = {
+        toplevel: false,
+        webkit: true,
+    }
+    input: {
+        "use strict";
+        let l = null;
+        for (let i = 0; i < 1; i++)
+            console.log(i);
+    }
+    expect: {
+        "use strict";
+        let l = null;
+        for (let i = 0; i < 1; i++)
+            console.log(i);
+    }
+    expect_stdout: "0"
+    node_version: ">=4"
+}
+
+issue_1753_toplevel: {
+    mangle = {
+        toplevel: true,
+        webkit: true,
+    }
+    input: {
+        "use strict";
+        let l = null;
+        for (let i = 0; i < 1; i++)
+            console.log(i);
+    }
+    expect: {
+        "use strict";
+        let l = null;
+        for (let e = 0; e < 1; e++)
+            console.log(e);
+    }
+    expect_stdout: "0"
+    node_version: ">=4"
+}
+
+issue_5032_await: {
+    options = {
+        merge_vars: true,
+        webkit: false,
+    }
+    input: {
+        function log(value) {
+            console.log(value);
+            return value;
+        }
+        async function f(a) {
+            var b = log(a), c = b;
+            log(b);
+            log(c);
+        }
+        f("PASS");
+    }
+    expect: {
+        function log(value) {
+            console.log(value);
+            return value;
+        }
+        async function f(a) {
+            var a = log(a), c = a;
+            log(a);
+            log(c);
+        }
+        f("PASS");
+    }
+    expect_stdout: [
+        "PASS",
+        "PASS",
+        "PASS",
+    ]
+    node_version: ">=8"
+}
+
+issue_5032_await_webkit: {
+    options = {
+        merge_vars: true,
+        webkit: true,
+    }
+    input: {
+        function log(value) {
+            console.log(value);
+            return value;
+        }
+        async function f(a) {
+            var b = log(a), c = b;
+            log(b);
+            log(c);
+        }
+        f("PASS");
+    }
+    expect: {
+        function log(value) {
+            console.log(value);
+            return value;
+        }
+        async function f(a) {
+            var b = log(a), c = b;
+            log(b);
+            log(c);
+        }
+        f("PASS");
+    }
+    expect_stdout: [
+        "PASS",
+        "PASS",
+        "PASS",
+    ]
+    node_version: ">=8"
+}
+
+issue_5032_yield: {
+    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_yield_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_5480: {
+    mangle = {
+        webkit: true,
+    }
+    input: {
+        "use strict";
+        L: for (let a in console.log("PASS"));
+    }
+    expect: {
+        "use strict";
+        o: for (let o in console.log("PASS"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
--- 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() {
@@ -737,7 +749,7 @@ lift_sequence: {
    node_version: ">=4"
 }

-inline_nested_yield: {
+inline_nested: {
    options = {
        inline: true,
        sequences: true,
@@ -772,6 +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,
@@ -852,8 +976,8 @@ issue_4454_2: {
        f("PASS");
    }
    expect: {
-        function f(b) {
-            (function*(c = console.log(b)) {})();
+        function f(a) {
+            (function*(c = console.log(a)) {})();
            var b = 42..toString();
            console.log(b);
        }
@@ -958,7 +1082,7 @@ issue_4639_1: {
        }().next().value());
    }
    expect_stdout: "PASS"
-    node_version: ">=4"
+    node_version: ">=4 <7 || >=8.7.0"
 }

 issue_4639_2: {
@@ -1143,80 +1267,6 @@ issue_5019_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(c) {
-            var b = log(c), c = b;
-            log(b);
-            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,
@@ -1247,12 +1297,13 @@ issue_5034: {
    node_version: ">=4"
 }

-issue_5076: {
+issue_5076_1: {
    options = {
        evaluate: true,
        hoist_vars: true,
-        passes: 2,
+        keep_fargs: false,
        pure_getters: "strict",
+        sequences: true,
        side_effects: true,
        toplevel: true,
        unused: true,
@@ -1269,9 +1320,198 @@ issue_5076: {
    }
    expect: {
        var a;
-        console.log("PASS");
+        console.log("PASS"),
        a = 42["a"];
    }
    expect_stdout: "PASS"
    node_version: ">=6"
 }
+
+issue_5076_2: {
+    options = {
+        evaluate: true,
+        hoist_vars: true,
+        keep_fargs: false,
+        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"
+}
+
+issue_5385_1: {
+    options = {
+        inline: true,
+    }
+    input: {
+        (async function*() {
+            (function() {
+                try {
+                    return console.log("foo");
+                } finally {
+                    return console.log("bar");
+                }
+                console.log("baz");
+            })();
+        })().next();
+        console.log("moo");
+    }
+    expect: {
+        (async function*() {
+            (function() {
+                try {
+                    return console.log("foo");
+                } finally {
+                    return console.log("bar");
+                }
+                console.log("baz");
+            })();
+        })().next();
+        console.log("moo");
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+        "moo",
+    ]
+    node_version: ">=10"
+}
+
+issue_5385_2: {
+    options = {
+        inline: true,
+    }
+    input: {
+        (async function*() {
+            return function() {
+                try {
+                    return console.log("foo");
+                } finally {
+                    return console.log("bar");
+                }
+            }();
+        })().next();
+        console.log("moo");
+    }
+    expect: {
+        (async function*() {
+            return function() {
+                try {
+                    return console.log("foo");
+                } finally {
+                    return console.log("bar");
+                }
+            }();
+        })().next();
+        console.log("moo");
+    }
+    expect_stdout: [
+        "foo",
+        "bar",
+        "moo",
+    ]
+    node_version: ">=10"
+}
+
+issue_5425: {
+    options = {
+        assignments: true,
+        ie: true,
+        toplevel: true,
+        unused: true,
+        yields: true,
+    }
+    input: {
+        var a = "FAIL";
+        var b = function* f() {}(a ? a = "PASS" : 42);
+        console.log(a, typeof f);
+    }
+    expect: {
+        var a = "FAIL";
+        (function* f() {})(a && (a = "PASS"));
+        console.log(a, typeof f);
+    }
+    expect_stdout: "PASS undefined"
+    node_version: ">=4"
+}
+
+issue_5456: {
+    options = {
+        inline: true,
+        merge_vars: true,
+    }
+    input: {
+        var a = true;
+        (function() {
+            (function(b, c) {
+                var d = function*() {
+                    c = null;
+                }();
+                var e = function() {
+                    if (c)
+                        console.log(typeof d);
+                    while (b);
+                }();
+            })(function(i) {
+                return console.log("foo") && i;
+            }(a));
+        })();
+    }
+    expect: {
+        var a = true;
+        (function() {
+            b = (i = a, console.log("foo") && i),
+            d = function*() {
+                c = null;
+            }(),
+            e = function() {
+                if (c) console.log(typeof d);
+                while (b);
+            }(),
+            void 0;
+            var b, c, d, e;
+            var i;
+        })();
+    }
+    expect_stdout: "foo"
+    node_version: ">=4"
+}
--- a/test/input/invalid/optional-template.js
+++ b/test/input/invalid/optional-template.js
@@ -0,0 +1 @@
+console?.log``;
--- a/test/input/issue-505/output.js
+++ b/test/input/issue-505/output.js
@@ -1,5 +1,5 @@
 function test(a){
-"aaaaaaaaaaaaaaaa"
-;a(err,data),a(err,
+"aaaaaaaaaaaaaaaa";
+a(err,data),a(err,
 data)}
-//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIjAiXSwibmFtZXMiOlsidGVzdCIsImNhbGxiYWNrIiwiZXJyIiwiZGF0YSJdLCJtYXBwaW5ncyI6IkFBQUEsU0FBU0EsS0FBS0M7O0NBRVZBLEVBQVNDLElBQUtDLE1BQ2RGLEVBQVNDO0FBQUtDIn0=
+//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIjAiXSwibmFtZXMiOlsidGVzdCIsImNhbGxiYWNrIiwiZXJyIiwiZGF0YSJdLCJtYXBwaW5ncyI6IkFBQUEsU0FBU0E7SEFBS0M7QUFFVkE7aEJBQVNDLElBQUtDLE1BQ2RGLEVBQVNDLElBQUtDIn0=
--- a/test/input/module/expect.js
+++ b/test/input/module/expect.js
@@ -0,0 +1 @@
+function n(){return this||arguments[0]+arguments[1]}function o(){return this||arguments[0]+arguments[1]}console.log(n(n(1,3),5)),console.log(o(o(2,4),6));
--- a/test/input/module/input.js
+++ b/test/input/module/input.js
@@ -0,0 +1,13 @@
+console.log(function() {
+    function sum(...params) {
+        return this || arguments[0] + arguments[1];
+    }
+    return sum(sum(1, 3), 5);
+}());
+console.log(function() {
+    "use strict";
+    function sum(...params) {
+        return this || arguments[0] + arguments[1];
+    }
+    return sum(sum(2, 4), 6);
+}());
--- 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/input/reduce/export_default.js
+++ b/test/input/reduce/export_default.js
@@ -0,0 +1,17 @@
+var unused;
+export default class {
+    ____11111() {
+        a, b, c, d, e;
+        f, g, h, i, j;
+        k, l, m, n, o;
+        p, q, r, s, t;
+        u, v, w, x, y, z;
+        A, B, C, D, E;
+        F, G, H, I, J;
+        K, L, M, N, O;
+        P, Q, R, S, T;
+        U, V, W, X, Y, Z;
+        $, _;
+        unused;
+    }
+}
--- a/test/jetstream.js
+++ b/test/jetstream.js
@@ -68,6 +68,8 @@ if (typeof phantom == "undefined") {
        (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",
--- a/test/mocha/awaits.js
+++ b/test/mocha/awaits.js
@@ -7,7 +7,7 @@ describe("async", function() {
            "function await() {}",
            "function(await) {}",
            "function() { await; }",
-            "function() { await:{} }",
+            "function() { await: {} }",
            "function() { var await; }",
            "function() { function await() {} }",
            "function() { try {} catch (await) {} }",
--- 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();
        });
    });
@@ -721,6 +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,
@@ -886,6 +928,14 @@ describe("bin/uglifyjs", function() {
            done();
        });
    });
+    it("Should work with --module", function(done) {
+        var command = uglifyjscmd + " test/input/module/input.js --module -mc";
+        exec(command, function(err, stdout, stderr) {
+            if (err) throw err;
+            assert.strictEqual(stdout, read("test/input/module/expect.js"));
+            done();
+        });
+    });
    it("Should compress swarm of unused variables with reasonable performance", function(done) {
        var code = [
            "console.log(function() {",
--- 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/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);
@@ -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");
@@ -282,35 +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;
@@ -414,4 +418,71 @@ describe("test/reduce.js", function() {
        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"));
+    });
+    it("Should transform `export default class` correctly", function() {
+        var result = reduce_test(read("test/input/reduce/export_default.js"), {
+            compress: false,
+            toplevel: true,
+        });
+        if (result.error) throw result.error;
+        assert.strictEqual(result.code, [
+            "// Can't reproduce test failure",
+            "// minify options: {",
+            '//   "compress": false,',
+            '//   "toplevel": true',
+            "// }",
+        ].join("\n"));
+    });
+    it("Should transform `export default function` correctly", function() {
+        var code = [
+            "for (var k in this)",
+            "    console.log(k);",
+            "export default (function f() {});",
+            "console.log(k);",
+        ].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 transform `export default (42)` correctly", function() {
+        var code = [
+            "export default (42);",
+            "for (var k in this)",
+            "    console.log(k);",
+        ].join("\n");
+        var result = reduce_test(code, {
+            compress: false,
+            mangle: false,
+        });
+        if (result.error) throw result.error;
+        assert.strictEqual(result.code, [
+            "// Can't reproduce test failure",
+            "// minify options: {",
+            '//   "compress": false,',
+            '//   "mangle": false',
+            "// }",
+        ].join("\n"));
+    });
 });
--- a/test/mocha/sourcemaps.js
+++ b/test/mocha/sourcemaps.js
@@ -205,8 +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" ]);
        });
@@ -362,7 +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/mocha/yields.js
+++ b/test/mocha/yields.js
@@ -6,7 +6,7 @@ describe("generator", function() {
        [
            "function yield() {}",
            "function(yield) {}",
-            "function() { yield:{} }",
+            "function() { yield: {} }",
            "function() { var yield; }",
            "function() { function yield() {} }",
            "function() { try {} catch (yield) {} }",
--- a/test/reduce.js
+++ b/test/reduce.js
--- a/test/release/web-tooling-benchmark.sh
+++ b/test/release/web-tooling-benchmark.sh
@@ -54,7 +54,7 @@ ERR=$?; if [ "$ERR" != "0" ]; then echo "Error: $ERR"; exit $ERR; fi
 minify_in_situ "src" \
 && minify_in_situ "third_party" \
 && rm -rf node_modules \
-&& npm_install \
+&& npm_install --package-lock \
 && rm -rf build/* \
 && npm run build:terser-bundled \
 && npm run build:uglify-js-bundled \
--- a/test/sandbox.js
+++ b/test/sandbox.js
@@ -26,9 +26,11 @@ exports.run_code = semver.satisfies(process.version, "0.8") ? function(code, top
    return stdout;
 } : semver.satisfies(process.version, "<0.12") ? run_code_vm : function(code, toplevel, timeout) {
    if ([
-        /\basync[ \t]*\([\s\S]*?\)[ \t]*=>/,
        /\b(async[ \t]+function|Promise|setImmediate|setInterval|setTimeout)\b/,
-        /\basync([ \t]+|[ \t]*#|[ \t]*\*[ \t]*)[^\s()[\]{},.&|!~=*%/+-]+(\s*\(|[ \t]*=>)/,
+        /\basync([ \t]+|[ \t]*#)[^\s()[\]{}#:;,.&|!~=*%/+-]+(\s*\(|[ \t]*=>)/,
+        /\basync[ \t]*\*[ \t]*[^\s()[\]{}#:;,.&|!~=*%/+-]+\s*\(/,
+        /\basync([ \t]*\*)?[ \t]*\[[\s\S]*?\]\s*\(/,
+        /\basync[ \t]*\([\s\S]*?\)[ \t]*=>/,
    ].some(function(pattern) {
        return pattern.test(code);
    })) {
@@ -50,14 +52,22 @@ exports.same_stdout = semver.satisfies(process.version, "0.12") ? function(expec
    return typeof expected == typeof actual && strip_func_ids(expected) == strip_func_ids(actual);
 };
 exports.patch_module_statements = function(code) {
-    var count = 0, imports = [];
-    code = code.replace(/\bexport(?:\s*\{[^}]*}\s*?(?:$|\n|;)|\s+default\b(?:\s*(\(|\{|class\s*\{|class\s+(?=extends\b)|(?:async\s+)?function\s*(?:\*\s*)?\())?|\b)/g, function(match, header) {
+    var count = 0, has_default = "", imports = [], strict_mode = "";
+    code = code.replace(/^\s*("|')use strict\1\s*;?/, function(match) {
+        strict_mode = match;
+        return "";
+    }).replace(/\bexport(?:\s*\{[^{}]*}\s*?(?:$|\n|;)|\s+default\b(?:\s*(\(|\{|class\s*\{|class\s+(?=extends\b)|(?:async\s+)?function\s*(?:\*\s*)?\())?|\b)/g, function(match, header) {
+        if (/^export\s+default/.test(match)) has_default = "var _uglify_export_default_;";
        if (!header) return "";
        if (header.length == 1) return "0, " + header;
-        return header.slice(0, -1) + " _" + ++count + header.slice(-1);
+        var name = "_uglify_export_default_";
+        if (/^class\b/.test(header)) do {
+            name = "_uglify_export_default_" + ++count;
+        } while (code.indexOf(name) >= 0);
+        return header.slice(0, -1) + " " + name + header.slice(-1);
    }).replace(/\bimport\.meta\b/g, function() {
        return '({ url: "https://example.com/path/index.html" })';
-    }).replace(/\bimport\b(?:\s*([^('"]+)\bfrom\b)?\s*(['"]).*?\2(?:$|\n|;)/g, function(match, symbols) {
+    }).replace(/\bimport\b(?:\s*([^\s('"][^('"]*)\bfrom\b)?\s*(['"]).*?\2(?:$|\n|;)/g, function(match, symbols) {
        if (symbols) {
            if (!/^[{*]/.test(symbols)) symbols = "default:" + symbols;
            symbols = symbols.replace(/[{}]/g, "").trim().replace(/\s*,\s*/g, ",");
@@ -71,7 +81,7 @@ exports.patch_module_statements = function(code) {
        return "";
    });
    imports.push("");
-    return imports.join("\n") + code;
+    return strict_mode + has_default + imports.join("\n") + code;
 };

 function is_error(result) {
@@ -146,7 +156,8 @@ function setup(global, builtins, setup_log, setup_tty) {
                    delete ex[name];
                }
            }
-            process.stderr.write(inspect(value) + "\n\n-----===== UNCAUGHT EXCEPTION =====-----\n\n");
+            var marker = "\n\n-----===== UNCAUGHT EXCEPTION =====-----\n\n";
+            process.stderr.write(marker + inspect(value) + marker);
            throw ex;
        }).on("unhandledRejection", function() {});
    }
@@ -202,13 +213,11 @@ function setup(global, builtins, setup_log, setup_tty) {
    });
    Object.defineProperties(global, props);
    // for Node.js v8+
-    if (global.toString !== Object.prototype.toString) {
-        global.__proto__ = Object.defineProperty(Object.create(global.__proto__), "toString", {
-            value: function() {
-                return "[object global]";
-            },
-        });
-    }
+    global.__proto__ = Object.defineProperty(Object.create(global.__proto__), "toString", {
+        value: function() {
+            return "[object global]";
+        },
+    });

    function self() {
        return this;
@@ -254,8 +263,11 @@ function run_code_vm(code, toplevel, timeout) {
        var ctx = vm.createContext({ console: console });
        // for Node.js v6
        vm.runInContext(setup_code, ctx);
-        vm.runInContext(toplevel ? "(function(){" + code + "})();" : code, ctx, { timeout: timeout });
-        return strip_color_codes(stdout);
+        vm.runInContext(toplevel ? "(function(){\n" + code + "\n})();" : code, ctx, { timeout: timeout });
+        // for Node.js v4
+        return strip_color_codes(stdout.replace(/\b(Array \[|Object {)/g, function(match) {
+            return match.slice(-1);
+        }));
    } catch (ex) {
        return ex;
    } finally {
@@ -265,7 +277,7 @@ function run_code_vm(code, toplevel, timeout) {

 function run_code_exec(code, toplevel, timeout) {
    if (toplevel) {
-        code = setup_code + "(function(){" + code + "})();";
+        code = setup_code + "(function(){\n" + code + "\n})();";
    } else {
        code = code.replace(/^((["'])[^"']*\2(;|$))?/, function(directive) {
            return directive + setup_code;
@@ -278,22 +290,26 @@ function run_code_exec(code, toplevel, timeout) {
        timeout: timeout || 5000,
    });
    if (result.status === 0) return result.stdout;
+    var msg = ("" + result.stderr).replace(/\r\n/g, "\n");
    if (result.error && result.error.code == "ETIMEDOUT" || /FATAL ERROR:/.test(msg)) {
        return new Error("Script execution timed out.");
    }
    if (result.error) return result.error;
-    var msg = result.stderr.replace(/\r\n/g, "\n");
-    var end = msg.indexOf("\n\n-----===== UNCAUGHT EXCEPTION =====-----\n\n");
+    var match = /\n([^:\s]*Error)(?:: ([\s\S]+?))?\n(    at [\s\S]+)\n$/.exec(msg);
+    var marker = "\n\n-----===== UNCAUGHT EXCEPTION =====-----\n\n";
+    var start = msg.indexOf(marker) + marker.length;
+    var end = msg.indexOf(marker, start);
    var details;
    if (end >= 0) {
-        details = msg.slice(0, end).replace(/<([1-9][0-9]*) empty items?>/g, function(match, count) {
+        details = msg.slice(start, end).replace(/<([1-9][0-9]*) empty items?>/g, function(match, count) {
            return new Array(+count).join();
        });
        try {
            details = vm.runInNewContext("(" + details + ")");
        } catch (e) {}
+    } else if (!match) {
+        return new Error("Script execution aborted.");
    }
-    var match = /\n([^:\s]*Error)(?:: ([\s\S]+?))?\n(    at [\s\S]+)\n$/.exec(msg);
    if (!match) return details;
    var ex = new global[match[1]](match[2]);
    ex.stack = ex.stack.slice(0, ex.stack.indexOf("    at ")) + match[3];
--- a/test/ufuzz/index.js
+++ b/test/ufuzz/index.js
@@ -128,7 +128,7 @@ for (var i = 2; i < process.argv.length; ++i) {

 var SUPPORT = function(matrix) {
    for (var name in matrix) {
-        matrix[name] = typeof sandbox.run_code(matrix[name]) == "string";
+        matrix[name] = !sandbox.is_error(sandbox.run_code(matrix[name]));
    }
    return matrix;
 }({
@@ -334,6 +334,7 @@ var VAR_NAMES = [
    "arguments",
    "async",
    "await",
+    "let",
    "yield",
 ];
 var INITIAL_NAMES_LEN = VAR_NAMES.length;
@@ -352,7 +353,7 @@ var TYPEOF_OUTCOMES = [
 ];

 var avoid_vars = [];
-var block_vars = [];
+var block_vars = [ "let" ];
 var lambda_vars = [];
 var unique_vars = [];
 var classes = [];
@@ -399,7 +400,7 @@ function mayDefer(code) {

 function createTopLevelCode() {
    VAR_NAMES.length = INITIAL_NAMES_LEN; // prune any previous names still in the list
-    block_vars.length = 0;
+    block_vars.length = 1;
    lambda_vars.length = 0;
    unique_vars.length = 0;
    classes.length = 0;
@@ -1804,7 +1805,7 @@ function createClassLiteral(recurmax, stmtDepth, canThrow, name) {
        if (canThrow && rng(20) == 0) {
            s += p;
        } else {
-            s += "(" + p + " && " + p + ".constructor === Function ? " + p + " : function() {})";
+            s += "(typeof " + p + ' == "function" && typeof ' + p + '.prototype == "object" && ' + p + ".constructor === Function ? " + p + " : function() {})";
        }
    }
    s += " {\n";
@@ -1823,9 +1824,15 @@ function createClassLiteral(recurmax, stmtDepth, canThrow, name) {
            declared.push(internal);
        }
        if (SUPPORT.class_field && rng(2)) {
-            s += internal || createObjectKey(recurmax, stmtDepth, canThrow);
+            if (internal) {
+                s += internal;
+            } else if (fixed && bug_class_static_nontrivial) {
+                s += getDotKey();
+            } else {
+                s += createObjectKey(recurmax, stmtDepth, canThrow);
+            }
            if (rng(5)) {
-                async = bug_async_class_await && fixed && 0;
+                async = false;
                generator = false;
                s += " = " + createExpression(recurmax, NO_COMMA, stmtDepth, fixed ? canThrow : CANNOT_THROW);
                generator = save_generator;
@@ -2027,9 +2034,10 @@ function removeAvoidVar(name) {
 function isBannedKeyword(name) {
    switch (name) {
      case "arguments":
+      case "let":
        return in_class;
      case "await":
-        return async !== false;
+        return async || in_class && bug_class_static_await;
      case "yield":
        return generator || in_class;
    }
@@ -2078,8 +2086,8 @@ if (require.main !== module) {
    return;
 }

-function run_code(code, toplevel) {
-    return sandbox.run_code(sandbox.patch_module_statements(code), toplevel);
+function run_code(code, toplevel, timeout) {
+    return sandbox.run_code(sandbox.patch_module_statements(code), toplevel, timeout);
 }

 function writeln(stream, msg) {
@@ -2108,7 +2116,7 @@ function try_beautify(code, toplevel, result, printfn, options) {
    } else if (options) {
        var uglified = UglifyJS.minify(beautified.code, JSON.parse(options));
        var expected, actual;
-        if (typeof uglify_code != "string" || uglified.error) {
+        if (sandbox.is_error(uglify_code) || uglified.error) {
            expected = uglify_code;
            actual = uglified.error;
        } else {
@@ -2137,7 +2145,7 @@ function log_suspects(minify_options, component) {
    var defs = default_options[component];
    var toplevel = sandbox.has_toplevel(minify_options);
    var suspects = Object.keys(defs).filter(function(name) {
-        var flip = name == "keep_fargs";
+        var flip = component == "compress" && name == "keep_fargs";
        if (flip !== (name in options ? options : defs)[name]) {
            var m = JSON.parse(JSON.stringify(minify_options));
            var o = JSON.parse(JSON.stringify(options));
@@ -2145,7 +2153,7 @@ function log_suspects(minify_options, component) {
            m[component] = o;
            m.validate = true;
            var result = UglifyJS.minify(original_code, m);
-            if (typeof uglify_code != "string") {
+            if (sandbox.is_error(uglify_code)) {
                return !sandbox.same_stdout(uglify_code, result.error);
            } else if (result.error) {
                errorln("Error testing options." + component + "." + name);
@@ -2173,7 +2181,7 @@ function log_suspects_global(options, toplevel) {
        m[component] = false;
        m.validate = true;
        var result = UglifyJS.minify(original_code, m);
-        if (typeof uglify_code != "string") {
+        if (sandbox.is_error(uglify_code)) {
            return !sandbox.same_stdout(uglify_code, result.error);
        } else if (result.error) {
            errorln("Error testing options." + component);
@@ -2202,7 +2210,16 @@ function log(options) {
    errorln();
    errorln();
    errorln("//-------------------------------------------------------------");
-    if (typeof uglify_code == "string") {
+    if (sandbox.is_error(uglify_code)) {
+        errorln("// !!! uglify failed !!!");
+        errorln(uglify_code);
+        if (original_erred) {
+            errorln();
+            errorln();
+            errorln("original stacktrace:");
+            errorln(original_result);
+        }
+    } else {
        errorln("// uglified code");
        try_beautify(uglify_code, toplevel, uglify_result, errorln);
        errorln();
@@ -2211,15 +2228,6 @@ function log(options) {
        errorln(original_result);
        errorln("uglified result:");
        errorln(uglify_result);
-    } else {
-        errorln("// !!! uglify failed !!!");
-        errorln(uglify_code);
-        if (errored) {
-            errorln();
-            errorln();
-            errorln("original stacktrace:");
-            errorln(original_result);
-        }
    }
    errorln("//-------------------------------------------------------------");
    if (!ok) {
@@ -2288,7 +2296,7 @@ function fuzzy_match(original, uglified) {
    return true;

    function collect(input, nums) {
-        return input.replace(/-?([1-9][0-9]*(\.[0-9]+)?|0\.[0-9]+)(e-?[1-9][0-9]*)?/ig, function(num) {
+        return input.replace(/-?([1-9][0-9]*(\.[0-9]+)?|0\.[0-9]+)(e-?[1-9][0-9]*)?/gi, function(num) {
            return "<|" + nums.push(+num) + "|>";
        });
    }
@@ -2316,20 +2324,28 @@ function is_error_in(ex) {
    return ex.name == "TypeError" && /'in'/.test(ex.message);
 }

+function is_error_tdz(ex) {
+    return ex.name == "ReferenceError";
+}
+
 function is_error_spread(ex) {
-    return ex.name == "TypeError" && /Found non-callable @@iterator| is not iterable| not a function/.test(ex.message);
+    return ex.name == "TypeError" && /Found non-callable @@iterator| is not iterable| not a function|Symbol\(Symbol\.iterator\)/.test(ex.message);
 }

 function is_error_recursion(ex) {
    return ex.name == "RangeError" && /Invalid string length|Maximum call stack size exceeded/.test(ex.message);
 }

+function is_error_set_property(ex) {
+    return ex.name == "TypeError" && /^Cannot set propert[\s\S]+? of (null|undefined)/.test(ex.message);
+}
+
 function is_error_redeclaration(ex) {
    return ex.name == "SyntaxError" && /already been declared|redeclaration/.test(ex.message);
 }

 function is_error_destructuring(ex) {
-    return ex.name == "TypeError" && /^Cannot destructure /.test(ex.message);
+    return ex.name == "TypeError" && /^Cannot (destructure|read propert)/.test(ex.message);
 }

 function is_error_class_constructor(ex) {
@@ -2343,6 +2359,8 @@ function is_error_getter_only_property(ex) {
 }

 function patch_try_catch(orig, toplevel) {
+    var patched = Object.create(null);
+    var patches = [];
    var stack = [ {
        code: orig,
        index: 0,
@@ -2350,7 +2368,7 @@ function patch_try_catch(orig, toplevel) {
        tries: [],
    } ];
    var tail_throw = '\nif (typeof UFUZZ_ERROR == "object") throw UFUZZ_ERROR;\n';
-    var re = /(?:(?:^|[\s{}):;])try|}\s*catch\s*\(([^)[{]+)\)|}\s*finally)\s*(?={)/g;
+    var re = /(?:(?:^|[\s{}):;])try|}\s*catch\s*\(([^()[{]+)\)|}\s*finally)\s*(?={)/g;
    while (stack.length) {
        var code = stack[0].code;
        var offset = stack[0].offset;
@@ -2380,7 +2398,7 @@ function patch_try_catch(orig, toplevel) {
                    "throw " + match[1] + ";",
                ].join("\n");
            }
-            var new_code = code.slice(0, index) + insert + code.slice(index) + tail_throw;
+            var new_code = code.slice(0, index) + insert + code.slice(index) + tail_throw + "var UFUZZ_ERROR;";
            var result = run_code(new_code, toplevel);
            if (!sandbox.is_error(result)) {
                if (!stack.filled && match[1]) stack.push({
@@ -2392,27 +2410,35 @@ function patch_try_catch(orig, toplevel) {
                offset += insert.length;
                code = new_code;
            } else if (is_error_in(result)) {
-                index = result.ufuzz_catch;
-                return orig.slice(0, index) + result.ufuzz_var + ' = new Error("invalid `in`");' + orig.slice(index);
+                patch(result.ufuzz_catch, result.ufuzz_var + ' = new Error("invalid `in`");');
+            } else if (is_error_tdz(result)) {
+                patch(result.ufuzz_catch, result.ufuzz_var + ' = new Error("TDZ");');
            } else if (is_error_spread(result)) {
-                index = result.ufuzz_catch;
-                return orig.slice(0, index) + result.ufuzz_var + ' = new Error("spread not iterable");' + orig.slice(index);
+                patch(result.ufuzz_catch, result.ufuzz_var + ' = new Error("spread not iterable");');
            } else if (is_error_recursion(result)) {
-                index = result.ufuzz_try;
-                return orig.slice(0, index) + 'throw new Error("skipping infinite recursion");' + orig.slice(index);
+                patch(result.ufuzz_try, 'throw new Error("skipping infinite recursion");');
+            } else if (is_error_set_property(result)) {
+                patch(result.ufuzz_catch, result.ufuzz_var + ' = new Error("cannot set property");');
            } else if (is_error_destructuring(result)) {
-                index = result.ufuzz_catch;
-                return orig.slice(0, index) + result.ufuzz_var + ' = new Error("cannot destructure");' + orig.slice(index);
+                patch(result.ufuzz_catch, result.ufuzz_var + ' = new Error("cannot destructure");');
            } else if (is_error_class_constructor(result)) {
-                index = result.ufuzz_catch;
-                return orig.slice(0, index) + result.ufuzz_var + ' = new Error("missing new for class");' + orig.slice(index);
+                patch(result.ufuzz_catch, result.ufuzz_var + ' = new Error("missing new for class");');
            } else if (is_error_getter_only_property(result)) {
-                index = result.ufuzz_catch;
-                return orig.slice(0, index) + result.ufuzz_var + ' = new Error("setting getter-only property");' + orig.slice(index);
+                patch(result.ufuzz_catch, result.ufuzz_var + ' = new Error("setting getter-only property");');
            }
        }
        stack.filled = true;
    }
+    if (patches.length) return patches.reduce(function(code, patch) {
+        var index = patch[0];
+        return code.slice(0, index) + patch[1] + code.slice(index);
+    }, orig);
+
+    function patch(index, code) {
+        if (patched[index]) return;
+        patched[index] = true;
+        patches.unshift([ index, code ]);
+    }
 }

 var beautify_options = {
@@ -2424,22 +2450,23 @@ var beautify_options = {
    },
 };
 var minify_options = require("./options.json");
-if (typeof sandbox.run_code("A:if (0) B:; else B:;") != "string") {
+if (sandbox.is_error(sandbox.run_code("A:if (0) B:; else B:;"))) {
    minify_options.forEach(function(o) {
        if (!("mangle" in o)) o.mangle = {};
        if (o.mangle) o.mangle.v8 = true;
    });
 }
 var bug_async_arrow_rest = function() {};
-if (SUPPORT.arrow && SUPPORT.async && SUPPORT.rest && typeof sandbox.run_code("async (a = f(...[], b)) => 0;") != "string") {
+if (SUPPORT.arrow && SUPPORT.async && SUPPORT.rest && sandbox.is_error(sandbox.run_code("async (a = f(...[], b)) => 0;"))) {
    bug_async_arrow_rest = function(ex) {
        return ex.name == "SyntaxError" && ex.message == "Rest parameter must be last formal parameter";
    };
 }
-var bug_async_class_await = SUPPORT.async && SUPPORT.class_field && typeof sandbox.run_code("var await; async function f() { class A { static p = await; } }") != "string";
-var bug_for_of_async = SUPPORT.for_await_of && typeof sandbox.run_code("var async; for (async of []);") != "string";
-var bug_for_of_var = SUPPORT.for_of && SUPPORT.let && typeof sandbox.run_code("try {} catch (e) { for (var e of []); }") != "string";
-if (SUPPORT.destructuring && typeof sandbox.run_code("console.log([ 1 ], {} = 2);") != "string") {
+var bug_class_static_await = SUPPORT.async && SUPPORT.class_field && sandbox.is_error(sandbox.run_code("var await; class A { static p = await; }"));
+var bug_class_static_nontrivial = SUPPORT.class_field && sandbox.is_error(sandbox.run_code("class A { static 42; static get 42() {} }"));
+var bug_for_of_async = SUPPORT.for_await_of && sandbox.is_error(sandbox.run_code("var async; for (async of []);"));
+var bug_for_of_var = SUPPORT.for_of && SUPPORT.let && sandbox.is_error(sandbox.run_code("try {} catch (e) { for (var e of []); }"));
+if (SUPPORT.destructuring && sandbox.is_error(sandbox.run_code("console.log([ 1 ], {} = 2);"))) {
    beautify_options.output.v8 = true;
    minify_options.forEach(function(o) {
        if (!("output" in o)) o.output = {};
@@ -2448,7 +2475,7 @@ if (SUPPORT.destructuring && typeof sandbox.run_code("console.log([ 1 ], {} = 2)
 }
 beautify_options = JSON.stringify(beautify_options);
 minify_options = minify_options.map(JSON.stringify);
-var original_code, original_result, errored;
+var original_code, original_result, original_erred;
 var uglify_code, uglify_result, ok;
 for (var round = 1; round <= num_iterations; round++) {
    process.stdout.write(round + " of " + num_iterations + "\r");
@@ -2456,7 +2483,7 @@ for (var round = 1; round <= num_iterations; round++) {
    original_code = createTopLevelCode();
    var orig_result = [ run_code(original_code), run_code(original_code, true) ];
    if (orig_result.some(function(result, toplevel) {
-        if (typeof result == "string") return;
+        if (!sandbox.is_error(result)) return;
        println();
        println();
        println("//=============================================================");
@@ -2467,8 +2494,10 @@ for (var round = 1; round <= num_iterations; round++) {
        println("original result:");
        println(result);
        println();
-        // ignore v8 parser bug
-        return bug_async_arrow_rest(result);
+            // ignore v8 parser bug
+        return bug_async_arrow_rest(result)
+            // ignore runtime platform bugs
+            || result.message == "Script execution aborted.";
    })) continue;
    minify_options.forEach(function(options) {
        var o = JSON.parse(options);
@@ -2476,33 +2505,44 @@ for (var round = 1; round <= num_iterations; round++) {
        o.validate = true;
        uglify_code = UglifyJS.minify(original_code, o);
        original_result = orig_result[toplevel ? 1 : 0];
-        errored = typeof original_result != "string";
+        original_erred = sandbox.is_error(original_result);
        if (!uglify_code.error) {
            uglify_code = uglify_code.code;
            uglify_result = run_code(uglify_code, toplevel);
            ok = sandbox.same_stdout(original_result, uglify_result);
+            var uglify_erred = sandbox.is_error(uglify_result);
            // ignore v8 parser bug
-            if (!ok && bug_async_arrow_rest(uglify_result)) ok = true;
+            if (!ok && uglify_erred && bug_async_arrow_rest(uglify_result)) ok = true;
+            // ignore runtime platform bugs
+            if (!ok && uglify_erred && uglify_result.message == "Script execution aborted.") ok = true;
            // handle difference caused by time-outs
-            if (!ok && errored && is_error_timeout(original_result)) {
-                if (is_error_timeout(uglify_result)) {
-                    // ignore difference in error message
-                    ok = true;
-                } else {
+            if (!ok) {
+                if (original_erred && is_error_timeout(original_result)) {
+                    if (uglify_erred && is_error_timeout(uglify_result)) {
+                        // ignore difference in error message
+                        ok = true;
+                    } else {
+                        // ignore spurious time-outs
+                        if (!orig_result[toplevel ? 3 : 2]) orig_result[toplevel ? 3 : 2] = run_code(original_code, toplevel, 10000);
+                        ok = sandbox.same_stdout(orig_result[toplevel ? 3 : 2], uglify_result);
+                    }
+                } else if (uglify_erred && is_error_timeout(uglify_result)) {
                    // ignore spurious time-outs
-                    if (!orig_result[toplevel ? 3 : 2]) orig_result[toplevel ? 3 : 2] = run_code(original_code, toplevel, 10000);
-                    ok = sandbox.same_stdout(orig_result[toplevel ? 3 : 2], uglify_result);
+                    var waited_result = run_code(uglify_code, toplevel, 10000);
+                    ok = sandbox.same_stdout(original_result, waited_result);
                }
            }
            // ignore declaration order of global variables
            if (!ok && !toplevel) {
-                ok = sandbox.same_stdout(run_code(sort_globals(original_code)), run_code(sort_globals(uglify_code)));
+                if (!(original_erred && original_result.name == "SyntaxError") && !(uglify_erred && uglify_result.name == "SyntaxError")) {
+                    ok = sandbox.same_stdout(run_code(sort_globals(original_code)), run_code(sort_globals(uglify_code)));
+                }
            }
            // ignore numerical imprecision caused by `unsafe_math`
-            if (!ok && o.compress && o.compress.unsafe_math && typeof original_result == typeof uglify_result) {
-                if (typeof original_result == "string") {
+            if (!ok && o.compress && o.compress.unsafe_math) {
+                if (typeof original_result == "string" && typeof uglify_result == "string") {
                    ok = fuzzy_match(original_result, uglify_result);
-                } else if (sandbox.is_error(original_result)) {
+                } else if (original_erred && uglify_erred) {
                    ok = original_result.name == uglify_result.name && fuzzy_match(original_result.message, uglify_result.message);
                }
                if (!ok) {
@@ -2510,47 +2550,33 @@ for (var round = 1; round <= num_iterations; round++) {
                    ok = sandbox.same_stdout(fuzzy_result, uglify_result);
                }
            }
-            // ignore difference in error message caused by Temporal Dead Zone
-            if (!ok && errored && uglify_result.name == "ReferenceError" && original_result.name == "ReferenceError") ok = true;
-            // ignore difference due to implicit strict-mode in `class`
-            if (!ok && /\bclass\b/.test(original_code)) {
-                var original_strict = run_code('"use strict";\n' + original_code, toplevel);
-                var uglify_strict = run_code('"use strict";\n' + uglify_code, toplevel);
-                if (typeof original_strict != "string") {
-                    ok = typeof uglify_strict != "string";
-                } else {
-                    ok = sandbox.same_stdout(original_strict, uglify_strict);
-                }
-            }
-            // ignore difference in error message caused by `import` symbol redeclaration
-            if (!ok && errored && /\bimport\b/.test(original_code)) {
-                if (is_error_redeclaration(uglify_result) && is_error_redeclaration(original_result)) ok = true;
-            }
+            if (!ok && original_erred && uglify_erred && (
+                // ignore difference in error message caused by `in`
+                is_error_in(original_result) && is_error_in(uglify_result)
+                // ignore difference in error message caused by Temporal Dead Zone
+                || is_error_tdz(original_result) && is_error_tdz(uglify_result)
+                // ignore difference in error message caused by spread syntax
+                || is_error_spread(original_result) && is_error_spread(uglify_result)
+                // ignore difference in error message caused by destructuring assignment
+                || is_error_set_property(original_result) && is_error_set_property(uglify_result)
+                // ignore difference in error message caused by `import` symbol redeclaration
+                || /\bimport\b/.test(original_code) && is_error_redeclaration(original_result) && is_error_redeclaration(uglify_result)
+                // ignore difference in error message caused by destructuring
+                || is_error_destructuring(original_result) && is_error_destructuring(uglify_result)
+                // ignore difference in error message caused by call on class
+                || is_error_class_constructor(original_result) && is_error_class_constructor(uglify_result)
+                // ignore difference in error message caused by setting getter-only property
+                || is_error_getter_only_property(original_result) && is_error_getter_only_property(uglify_result)
+            )) ok = true;
            // ignore difference due to `__proto__` assignment
            if (!ok && /\b__proto__\b/.test(original_code)) {
                var original_proto = run_code("(" + patch_proto + ")();\n" + original_code, toplevel);
                var uglify_proto = run_code("(" + patch_proto + ")();\n" + uglify_code, toplevel);
                ok = sandbox.same_stdout(original_proto, uglify_proto);
            }
-            // ignore difference in error message caused by `in`
-            if (!ok && errored && is_error_in(uglify_result) && is_error_in(original_result)) ok = true;
-            // ignore difference in error message caused by spread syntax
-            if (!ok && errored && is_error_spread(uglify_result) && is_error_spread(original_result)) ok = true;
            // ignore difference in depth of termination caused by infinite recursion
-            if (!ok && errored && is_error_recursion(original_result)) {
-                if (is_error_recursion(uglify_result) || typeof uglify_result == "string") ok = true;
-            }
-            // ignore difference in error message caused by destructuring
-            if (!ok && errored && is_error_destructuring(uglify_result) && is_error_destructuring(original_result)) {
-                ok = true;
-            }
-            // ignore difference in error message caused by call on class
-            if (!ok && errored && is_error_class_constructor(uglify_result) && is_error_class_constructor(original_result)) {
-                ok = true;
-            }
-            // ignore difference in error message caused by setting getter-only property
-            if (!ok && errored && is_error_getter_only_property(uglify_result) && is_error_getter_only_property(original_result)) {
-                ok = true;
+            if (!ok && original_erred && is_error_recursion(original_result)) {
+                if (!uglify_erred || is_error_recursion(uglify_result)) ok = true;
            }
            // ignore errors above when caught by try-catch
            if (!ok) {
@@ -2562,7 +2588,7 @@ for (var round = 1; round <= num_iterations; round++) {
            }
        } else {
            uglify_code = uglify_code.error;
-            ok = errored && uglify_code.name == original_result.name;
+            ok = original_erred && uglify_code.name == original_result.name;
        }
        if (verbose || (verbose_interval && !(round % INTERVAL_COUNT)) || !ok) log(options);
        if (!ok && isFinite(num_iterations)) {
--- a/test/ufuzz/options.json
+++ b/test/ufuzz/options.json
@@ -26,6 +26,7 @@
            "passes": 1e6,
            "unsafe": true
        },
+        "keep_fargs": true,
        "keep_fnames": true,
        "toplevel": true
    },
				`@@ -0,0 +1 @@`
				`function n(){return this\|\|arguments[0]+arguments[1]}function o(){return this\|\|arguments[0]+arguments[1]}console.log(n(n(1,3),5)),console.log(o(o(2,4),6));`