v3.16.0

fixes #5485

.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

README.md

@@ -118,6 +118,7 @@ a double dash to prevent input files being used as option arguments:
     --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:
@@ -146,7 +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
@@ -517,6 +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
@@ -728,6 +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.
@@ -1331,11 +1338,9 @@ 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;
   }
-  }
   // SyntaxError: Unexpected reserved word
   ```
   UglifyJS may modify the input which in turn may suppress those errors.
@@ -1373,3 +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.

bin/uglifyjs

@@ -107,6 +107,7 @@ function process_option(name, no_value) {
                 "  --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.",
@@ -152,6 +153,7 @@ function process_option(name, no_value) {
       case "annotations":
       case "ie":
       case "ie8":
+      case "module":
       case "timings":
       case "toplevel":
       case "v8":

lib/ast.js

@@ -827,6 +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() {
@@ -851,9 +854,6 @@ var AST_DefClass = DEFNODE("DefClass", null, {
     $propdoc: {
         name: "[AST_SymbolDefClass] the name of this class",
     },
-    resolve: function(def_class) {
-        return def_class ? this : this.parent_scope.resolve();
-    },
     _validate: function() {
         if (!(this.name instanceof AST_SymbolDefClass)) throw new Error("name must be AST_SymbolDefClass");
     },
@@ -1837,7 +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", {
@@ -2039,16 +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);
         }
     },

lib/compress.js

@@ -80,6 +80,7 @@ function Compressor(options, false_by_default) {
         keep_infinity   : false,
         loops           : !false_by_default,
         merge_vars      : !false_by_default,
+        module          : false,
         negate_iife     : !false_by_default,
         objects         : !false_by_default,
         optional_chains : !false_by_default,
@@ -97,7 +98,7 @@ function Compressor(options, false_by_default) {
         switches        : !false_by_default,
         templates       : !false_by_default,
         top_retain      : null,
-        toplevel        : !!(options && options["top_retain"]),
+        toplevel        : !!(options && (options["module"] || options["top_retain"])),
         typeofs         : !false_by_default,
         unsafe          : false,
         unsafe_comps    : false,
@@ -130,6 +131,7 @@ function Compressor(options, false_by_default) {
         var escaped = def.escaped;
         return escaped && escaped.depth != 1;
     };
+    if (this.options["module"]) this.directives["use strict"] = true;
     var pure_funcs = this.options["pure_funcs"];
     if (typeof pure_funcs == "function") {
         this.pure_funcs = pure_funcs;
@@ -649,7 +651,7 @@ Compressor.prototype.compress = function(node) {
             }
             if (!HOP(tw.safe_ids, def.id)) {
                 if (!safe) return false;
-                if (safe.read) {
+                if (safe.read || tw.in_loop) {
                     var scope = tw.find_parent(AST_BlockScope);
                     if (scope instanceof AST_Class) return false;
                     if (def.scope.resolve() !== scope.resolve()) return false;
@@ -766,14 +768,14 @@ Compressor.prototype.compress = function(node) {
         function make_fixed_default(compressor, node, save) {
             var prev_save, prev_seq;
             return function() {
+                if (prev_seq === node) return node;
                 var current = save();
-                var ev;
-                if (!is_undefined(current, compressor) && (ev = fuzzy_eval(compressor, current, true)) !== undefined) {
-                    return ev instanceof AST_Node ? node : current;
-                }
-                if (prev_save !== current) {
+                var ev = fuzzy_eval(compressor, current, true);
+                if (ev instanceof AST_Node) {
+                    prev_seq = node;
+                } else if (prev_save !== current) {
                     prev_save = current;
-                    prev_seq = make_sequence(node, [ current, node.value ]);
+                    prev_seq = ev === undefined ? make_sequence(node, [ current, node.value ]) : current;
                 }
                 return prev_seq;
             };
@@ -1557,7 +1559,10 @@ Compressor.prototype.compress = function(node) {
 
     AST_SymbolRef.DEFMETHOD("is_immutable", function() {
         var def = this.redef || this.definition();
-        return (this.in_arg || def.orig.length == 1) && def.orig[0] instanceof AST_SymbolLambda;
+        if (!(def.orig[0] instanceof AST_SymbolLambda)) return false;
+        if (def.orig.length == 1) return true;
+        if (!this.in_arg) return false;
+        return !(def.orig[1] instanceof AST_SymbolFunarg);
     });
 
     AST_Node.DEFMETHOD("convert_symbol", noop);
@@ -2464,6 +2469,13 @@ Compressor.prototype.compress = function(node) {
                     abort = false;
                     return true;
                 }
+                if (node instanceof AST_Class) {
+                    if (!in_try) return false;
+                    var base = node.extends;
+                    if (!base) return false;
+                    if (base instanceof AST_SymbolRef) base = base.fixed_value();
+                    return !safe_for_extends(base);
+                }
                 if (node instanceof AST_Exit) {
                     if (in_try) {
                         if (in_try.bfinally) return true;
@@ -2552,8 +2564,8 @@ Compressor.prototype.compress = function(node) {
                     && all(iife.args, function(arg) {
                         return !(arg instanceof AST_Spread);
                     })) {
-                    var fn_strict = compressor.has_directive("use strict");
-                    if (fn_strict && !member(fn_strict, fn.body)) fn_strict = false;
+                    var fn_strict = fn.in_strict_mode(compressor)
+                        && !fn.parent_scope.resolve(true).in_strict_mode(compressor);
                     var has_await = is_async(fn) ? function(node) {
                         return node instanceof AST_Symbol && node.name == "await";
                     } : function(node) {
@@ -4120,6 +4132,25 @@ Compressor.prototype.compress = function(node) {
                 && !(compressor && node.expression.has_side_effects(compressor));
     }
 
+    // in_strict_mode()
+    // return true if scope executes in Strict Mode
+    (function(def) {
+        def(AST_Class, return_true);
+        def(AST_Scope, function(compressor) {
+            var body = this.body;
+            for (var i = 0; i < body.length; i++) {
+                var stat = body[i];
+                if (!(stat instanceof AST_Directive)) break;
+                if (stat.value == "use strict") return true;
+            }
+            var parent = this.parent_scope;
+            if (!parent) return compressor.option("module");
+            return parent.resolve(true).in_strict_mode(compressor);
+        });
+    })(function(node, func) {
+        node.DEFMETHOD("in_strict_mode", func);
+    });
+
     // is_truthy()
     // return true if `!!node === true`
     (function(def) {
@@ -6015,7 +6046,7 @@ Compressor.prototype.compress = function(node) {
     var NO_MERGE = makePredicate("arguments await yield");
     AST_Scope.DEFMETHOD("merge_variables", function(compressor) {
         if (!compressor.option("merge_vars")) return;
-        var in_try, root, segment = {}, self = this;
+        var in_arg = [], in_try, root, segment = {}, self = this;
         var first = [], last = [], index = 0;
         var declarations = new Dictionary();
         var references = Object.create(null);
@@ -6026,31 +6057,7 @@ Compressor.prototype.compress = function(node) {
                 var rhs = node.right;
                 if (lhs instanceof AST_Destructured) {
                     rhs.walk(tw);
-                    var marker = new TreeWalker(function(node) {
-                        if (node instanceof AST_Destructured) return;
-                        if (node instanceof AST_DefaultValue) {
-                            push();
-                            node.value.walk(tw);
-                            pop();
-                            node.name.walk(marker);
-                        } else if (node instanceof AST_DestructuredKeyVal) {
-                            if (node.key instanceof AST_Node) {
-                                push();
-                                segment.block = node;
-                                node.key.walk(tw);
-                                node.value.walk(marker);
-                                pop();
-                            } else {
-                                node.value.walk(marker);
-                            }
-                        } else if (node instanceof AST_SymbolRef) {
-                            mark(node);
-                        } else {
-                            node.walk(tw);
-                        }
-                        return true;
-                    });
-                    lhs.walk(marker);
+                    walk_destructured(AST_SymbolRef, mark, lhs);
                     return true;
                 }
                 if (lazy_op[node.operator.slice(0, -1)]) {
@@ -6081,18 +6088,15 @@ Compressor.prototype.compress = function(node) {
             }
             if (node instanceof AST_Call) {
                 var exp = node.expression;
-                var tail = exp.tail_node();
-                if (!(tail instanceof AST_LambdaExpression)) {
-                    descend();
-                    return mark_expression(exp);
-                }
-                if (exp !== tail) exp.expressions.slice(0, -1).forEach(function(node) {
-                    node.walk(tw);
-                });
+                if (exp instanceof AST_LambdaExpression) {
                     node.args.forEach(function(arg) {
                         arg.walk(tw);
                     });
-                tail.walk(tw);
+                    exp.walk(tw);
+                } else {
+                    descend();
+                    mark_expression(exp);
+                }
                 return true;
             }
             if (node instanceof AST_Class) {
@@ -6105,9 +6109,10 @@ Compressor.prototype.compress = function(node) {
                     if (prop.static) {
                         prop.value.walk(tw);
                     } else {
-                        push(tw);
+                        push();
+                        segment.block = node;
                         prop.value.walk(tw);
-                        pop(tw);
+                        pop();
                     }
                 });
                 return true;
@@ -6173,32 +6178,16 @@ Compressor.prototype.compress = function(node) {
                 if (node instanceof AST_Lambda) {
                     if (node.name) references[node.name.definition().id] = false;
                     var marker = node.uses_arguments && !tw.has_directive("use strict") ? function(node) {
-                        if (node instanceof AST_SymbolFunarg) references[node.definition().id] = false;
+                        references[node.definition().id] = false;
                     } : function(node) {
-                        if (node instanceof AST_SymbolFunarg) mark(node);
+                        mark(node);
                     };
-                    var scanner = new TreeWalker(function(ref) {
-                        if (ref instanceof AST_SymbolDeclaration) references[ref.definition().id] = false;
-                        if (!(ref instanceof AST_SymbolRef)) return;
-                        var def = ref.definition();
-                        var ldef = node.variables.get(ref.name);
-                        if (ldef && (ldef === def
-                            || def.undeclared
-                            || node.parent_scope.find_variable(ref.name) === def)) {
-                            references[def.id] = false;
-                            references[ldef.id] = false;
-                        } else {
-                            var save = segment;
-                            pop();
-                            mark(ref, true);
-                            segment = save;
-                        }
-                        return true;
-                    });
+                    in_arg.push(node);
                     node.argnames.forEach(function(argname) {
-                        argname.mark_symbol(marker, scanner);
+                        walk_destructured(AST_SymbolFunarg, marker, argname);
                     });
-                    if (node.rest) node.rest.mark_symbol(marker, scanner);
+                    if (node.rest) walk_destructured(AST_SymbolFunarg, marker, node.rest);
+                    in_arg.pop();
                 }
                 walk_lambda(node, tw);
                 pop();
@@ -6214,7 +6203,8 @@ Compressor.prototype.compress = function(node) {
                 } else {
                     descend();
                 }
-                return mark_expression(exp);
+                mark_expression(exp);
+                return true;
             }
             if (node instanceof AST_Switch) {
                 node.expression.walk(tw);
@@ -6246,9 +6236,7 @@ Compressor.prototype.compress = function(node) {
             if (node instanceof AST_Try) {
                 var save_try = in_try;
                 in_try = node;
-                var save = segment;
                 walk_body(node, tw);
-                segment = save;
                 if (node.bcatch) {
                     if (node.bcatch.argname) node.bcatch.argname.mark_symbol(function(node) {
                         if (node instanceof AST_SymbolCatch) {
@@ -6266,7 +6254,6 @@ Compressor.prototype.compress = function(node) {
                     }
                 }
                 in_try = save_try;
-                segment = save;
                 if (node.bfinally) node.bfinally.walk(tw);
                 return true;
             }
@@ -6316,12 +6303,10 @@ Compressor.prototype.compress = function(node) {
             }
 
             function mark_expression(exp) {
-                if (compressor.option("ie")) {
+                if (!compressor.option("ie")) return;
                 var sym = root_expr(exp);
                 if (sym instanceof AST_SymbolRef) sym.walk(tw);
             }
-                return true;
-            }
 
             function walk_cond(condition, consequent, alternative) {
                 var save = segment;
@@ -6416,8 +6401,45 @@ Compressor.prototype.compress = function(node) {
             segment = Object.getPrototypeOf(segment);
         }
 
+        function walk_destructured(symbol_type, mark, lhs) {
+            var marker = new TreeWalker(function(node) {
+                if (node instanceof AST_Destructured) return;
+                if (node instanceof AST_DefaultValue) {
+                    push();
+                    node.value.walk(tw);
+                    pop();
+                    node.name.walk(marker);
+                } else if (node instanceof AST_DestructuredKeyVal) {
+                    if (node.key instanceof AST_Node) {
+                        push();
+                        segment.block = node;
+                        node.key.walk(tw);
+                        node.value.walk(marker);
+                        pop();
+                    } else {
+                        node.value.walk(marker);
+                    }
+                } else if (node instanceof symbol_type) {
+                    mark(node);
+                } else {
+                    node.walk(tw);
+                }
+                return true;
+            });
+            lhs.walk(marker);
+        }
+
         function mark(sym, read) {
-            var def = sym.definition(), ldef, seg = segment;
+            var def = sym.definition(), ldef;
+            if (read && !all(in_arg, function(fn) {
+                ldef = fn.variables.get(sym.name);
+                if (!ldef) return true;
+                if (!is_funarg(ldef)) return true;
+                return ldef !== def
+                    && !def.undeclared
+                    && fn.parent_scope.find_variable(sym.name) !== def;
+            })) return references[def.id] = references[ldef.id] = false;
+            var seg = segment;
             if (in_try) {
                 push();
                 seg = segment;
@@ -6776,7 +6798,6 @@ Compressor.prototype.compress = function(node) {
             }
         });
         // pass 3: we should drop declarations not in_use
-        var unused_fn_names = [];
         var calls_to_drop_args = [];
         var fns_with_marked_args = [];
         var trimmer = new TreeTransformer(function(node) {
@@ -6897,7 +6918,7 @@ Compressor.prototype.compress = function(node) {
                 }
             }
             if (node instanceof AST_ClassExpression && node.name && drop_fn_name(node.name.definition())) {
-                unused_fn_names.push(node);
+                node.name = null;
             }
             if (node instanceof AST_Lambda) {
                 if (drop_funcs && node !== self && node instanceof AST_LambdaDefinition) {
@@ -6913,7 +6934,7 @@ Compressor.prototype.compress = function(node) {
                     }
                 }
                 if (node instanceof AST_LambdaExpression && node.name && drop_fn_name(node.name.definition())) {
-                    unused_fn_names.push(node);
+                    node.name = null;
                 }
                 if (!(node instanceof AST_Accessor)) {
                     var args, spread, trim = compressor.drop_fargs(node, parent);
@@ -6925,7 +6946,9 @@ Compressor.prototype.compress = function(node) {
                     }
                     var argnames = node.argnames;
                     var rest = node.rest;
+                    var after = false, before = false;
                     if (rest) {
+                        before = true;
                         if (!args || spread < argnames.length || rest instanceof AST_SymbolFunarg) {
                             rest = rest.transform(trimmer);
                         } else {
@@ -6938,8 +6961,7 @@ Compressor.prototype.compress = function(node) {
                             args.length = argnames.length;
                             if (trimmed.value.elements.length) [].push.apply(args, trimmed.value.elements);
                         }
-                        if (rest instanceof AST_Destructured && !rest.rest
-                            && (!node.uses_arguments || tt.has_directive("use strict"))) {
+                        if (rest instanceof AST_Destructured && !rest.rest) {
                             if (rest instanceof AST_DestructuredArray) {
                                 if (rest.elements.length == 0) rest = null;
                             } else if (rest.properties.length == 0) {
@@ -6947,9 +6969,13 @@ Compressor.prototype.compress = function(node) {
                             }
                         }
                         node.rest = rest;
-                        if (rest) trim = false;
+                        if (rest) {
+                            trim = false;
+                            after = true;
+                        }
                     }
                     var default_length = trim ? -1 : node.length();
+                    var trim_value = args && !node.uses_arguments && parent !== compressor.parent();
                     for (var i = argnames.length; --i >= 0;) {
                         var sym = argnames[i];
                         if (sym instanceof AST_SymbolFunarg) {
@@ -6964,29 +6990,43 @@ Compressor.prototype.compress = function(node) {
                                 sym.unused = true;
                             }
                         } else {
+                            before = true;
                             var funarg;
                             if (!args || spread < i) {
                                 funarg = sym.transform(trimmer);
                             } else {
-                                funarg = trim_destructured(sym, args[i], function(node) {
+                                var trimmed = trim_destructured(sym, args[i], function(node) {
                                     return node.definition().id in in_use_ids ? node : null;
-                                }, !node.uses_arguments, sym).name;
+                                }, trim_value, sym);
+                                funarg = trimmed.name;
+                                if (trimmed.value) args[i] = trimmed.value;
                             }
                             if (funarg) {
                                 trim = false;
+                                argnames[i] = funarg;
+                                if (!after) after = !(funarg instanceof AST_SymbolFunarg);
                             } else if (trim) {
                                 log_default(sym, "Dropping unused default argument {name}");
                                 argnames.pop();
                             } else if (i > default_length) {
                                 log_default(sym, "Dropping unused default argument assignment {name}");
-                                if (sym.name instanceof AST_SymbolFunarg) sym.name.unused = true;
+                                if (sym.name instanceof AST_SymbolFunarg) {
+                                    sym.name.unused = true;
+                                } else {
+                                    after = true;
+                                }
                                 argnames[i] = sym.name;
                             } else {
                                 log_default(sym, "Dropping unused default argument value {name}");
+                                argnames[i] = sym = sym.clone();
                                 sym.value = make_node(AST_Number, sym, { value: 0 });
+                                after = true;
                             }
                         }
                     }
+                    if (before && !after && node.uses_arguments && !tt.has_directive("use strict")) {
+                        node.rest = make_node(AST_DestructuredArray, node, { elements: [] });
+                    }
                     fns_with_marked_args.push(node);
                 }
             }
@@ -7210,6 +7250,7 @@ Compressor.prototype.compress = function(node) {
                             });
                             var index = indexOf_assign(sym, def);
                             if (index >= 0) assign_in_use[sym.id][index] = assign;
+                            sym.assignments++;
                             sym.eliminated++;
                             return assign;
                         }));
@@ -7285,6 +7326,13 @@ Compressor.prototype.compress = function(node) {
             }
         }, function(node, in_list) {
             if (node instanceof AST_BlockStatement) return trim_block(node, tt.parent(), in_list);
+            if (node instanceof AST_ExportDeclaration) {
+                var block = node.body;
+                if (!(block instanceof AST_BlockStatement)) return;
+                node.body = block.body.pop();
+                block.body.push(node);
+                return in_list ? List.splice(block.body) : block;
+            }
             if (node instanceof AST_For) return patch_for_init(node, in_list);
             if (node instanceof AST_ForIn) {
                 if (!drop_vars || !compressor.option("loops")) return;
@@ -7318,6 +7366,7 @@ Compressor.prototype.compress = function(node) {
             }
         });
         tt.push(compressor.parent());
+        tt.directives = Object.create(compressor.directives);
         self.transform(tt);
         if (self instanceof AST_Lambda
             && self.body.length == 1
@@ -7325,9 +7374,6 @@ Compressor.prototype.compress = function(node) {
             && self.body[0].value == "use strict") {
             self.body.length = 0;
         }
-        unused_fn_names.forEach(function(fn) {
-            fn.name = null;
-        });
         calls_to_drop_args.forEach(function(call) {
             drop_unused_call_args(call, compressor, fns_with_marked_args);
         });
@@ -7539,6 +7585,7 @@ Compressor.prototype.compress = function(node) {
                 var value = node.value.drop_side_effect_free(compressor);
                 if (!value) return null;
                 log(node.name, "Side effects in default value of unused variable {name}");
+                node = node.clone();
                 node.name.unused = null;
                 node.value = value;
             }
@@ -7616,6 +7663,7 @@ Compressor.prototype.compress = function(node) {
                     drop = save_drop;
                     if (values && newValues) {
                         fill_holes(value, newValues);
+                        value = value.clone();
                         value.elements = newValues;
                     }
                     if (!node.rest && (value instanceof AST_Array
@@ -7649,12 +7697,15 @@ Compressor.prototype.compress = function(node) {
                         drop = false;
                         value = value.fixed_value();
                     }
-                    var prop_keys, prop_map;
+                    var prop_keys, prop_map, values;
                     if (value instanceof AST_Object) {
                         prop_keys = [];
                         prop_map = new Dictionary();
-                        value.properties.forEach(function(prop, index) {
-                            if (prop instanceof AST_Spread) return prop_map = false;
+                        values = value.properties.map(function(prop, index) {
+                            prop = prop.clone();
+                            if (prop instanceof AST_Spread) {
+                                prop_map = false;
+                            } else {
                                 var key = prop.key;
                                 if (key instanceof AST_Node) key = key.evaluate(compressor, true);
                                 if (key instanceof AST_Node) {
@@ -7663,6 +7714,8 @@ Compressor.prototype.compress = function(node) {
                                     prop_map.set(key, prop);
                                 }
                                 prop_keys[index] = key;
+                            }
+                            return prop;
                         });
                     }
                     if (node.rest) {
@@ -7727,7 +7780,9 @@ Compressor.prototype.compress = function(node) {
                     });
                     value = save_value;
                     drop = save_drop;
-                    if (drop_keys && prop_keys) value.properties = List(value.properties, function(prop, index) {
+                    if (drop_keys && prop_keys) {
+                        value = value.clone();
+                        value.properties = List(values, function(prop, index) {
                             if (prop instanceof AST_Spread) return prop;
                             var key = prop_keys[index];
                             if (key instanceof AST_Node) return prop;
@@ -7748,6 +7803,7 @@ Compressor.prototype.compress = function(node) {
                                 value: make_node(AST_Number, prop, { value: 0 }),
                             }) : List.skip;
                         });
+                    }
                     if (value && !node.rest) switch (properties.length) {
                       case 0:
                         if (node === root) break;
@@ -8140,12 +8196,12 @@ Compressor.prototype.compress = function(node) {
         var self = this;
         var top_retain = self instanceof AST_Toplevel && compressor.top_retain || return_false;
         var defs_by_id = Object.create(null);
-        self.transform(new TreeTransformer(function(node, descend) {
+        var tt = new TreeTransformer(function(node, descend) {
             if (node instanceof AST_Assign) {
                 if (node.operator != "=") return;
                 if (!node.write_only) return;
                 if (!can_hoist(node.left, node.right, 1)) return;
-                descend(node, this);
+                descend(node, tt);
                 var defs = new Dictionary();
                 var assignments = [];
                 var decls = [];
@@ -8169,15 +8225,20 @@ Compressor.prototype.compress = function(node) {
                 });
                 defs.value = node.right;
                 defs_by_id[node.left.definition().id] = defs;
-                self.body.splice(self.body.indexOf(this.stack[1]) + 1, 0, make_node(AST_Var, node, {
+                self.body.splice(self.body.indexOf(tt.stack[1]) + 1, 0, make_node(AST_Var, node, {
                     definitions: decls,
                 }));
                 return make_sequence(node, assignments);
             }
-            if (node instanceof AST_Scope) return node === self ? undefined : node;
+            if (node instanceof AST_Scope) {
+                if (node === self) return;
+                var parent = tt.parent();
+                if (parent.TYPE == "Call" && parent.expression === node) return;
+                return node;
+            }
             if (node instanceof AST_VarDef) {
                 if (!can_hoist(node.name, node.value, 0)) return;
-                descend(node, this);
+                descend(node, tt);
                 var defs = new Dictionary();
                 var var_defs = [];
                 var decl = node.clone();
@@ -8199,7 +8260,8 @@ Compressor.prototype.compress = function(node) {
                 defs.set(key, new_var.definition());
                 return new_var;
             }
-        }));
+        });
+        self.transform(tt);
         self.transform(new TreeTransformer(function(node, descend) {
             if (node instanceof AST_PropAccess) {
                 if (!(node.expression instanceof AST_SymbolRef)) return;
@@ -8229,6 +8291,7 @@ Compressor.prototype.compress = function(node) {
             if (def.assignments != count) return;
             if (def.references.length - def.replaced == count) return;
             if (def.single_use) return;
+            if (self.find_variable(sym.name) !== def) return;
             if (top_retain(def)) return;
             if (sym.fixed_value() !== right) return;
             var fixed = sym.fixed || def.fixed;
@@ -8292,6 +8355,9 @@ Compressor.prototype.compress = function(node) {
                     var dropped = value.drop_side_effect_free(compressor);
                     if (dropped !== value) {
                         changed = true;
+                        if (dropped && async && !is_primitive(compressor, dropped)) {
+                            dropped = dropped.negate(compressor);
+                        }
                         node.value = dropped;
                     }
                 }
@@ -9100,6 +9166,7 @@ Compressor.prototype.compress = function(node) {
 
     function fuzzy_eval(compressor, node, nullish) {
         if (node.truthy) return true;
+        if (is_undefined(node)) return undefined;
         if (node.falsy && !nullish) return false;
         if (node.is_truthy()) return true;
         return node.evaluate(compressor, true);
@@ -9114,11 +9181,12 @@ Compressor.prototype.compress = function(node) {
             child = parent;
             parent = compressor.parent(level++);
             if (parent instanceof AST_Binary) {
-                var op = parent.operator;
-                if (!lazy_op[op]) return;
-                var left = parent.left;
-                if (left === child) continue;
-                if (match(left)) switch (op) {
+                switch (child) {
+                  case parent.left:
+                    if (lazy_op[parent.operator]) continue;
+                    break;
+                  case parent.right:
+                    if (match(parent.left)) switch (parent.operator) {
                       case "&&":
                         node[negated ? "falsy" : "truthy"] = true;
                         break;
@@ -9127,6 +9195,8 @@ Compressor.prototype.compress = function(node) {
                         node[negated ? "truthy" : "falsy"] = true;
                         break;
                     }
+                    break;
+                }
             } else if (parent instanceof AST_Conditional) {
                 var cond = parent.condition;
                 if (cond === child) continue;
@@ -9884,6 +9954,10 @@ Compressor.prototype.compress = function(node) {
         return safe;
     }
 
+    function safe_from_strict_mode(fn, compressor) {
+        return fn.in_strict_mode(compressor) || !compressor.has_directive("use strict");
+    }
+
     OPT(AST_Call, function(self, compressor) {
         var exp = self.expression;
         var terminated = trim_optional_chain(self, compressor);
@@ -10208,7 +10282,10 @@ Compressor.prototype.compress = function(node) {
             }
             return true;
         }) && !(fn.rest instanceof AST_Destructured && has_arg_refs(fn, fn.rest));
-        var can_inline = can_drop && compressor.option("inline") && !self.is_expr_pure(compressor);
+        var can_inline = can_drop
+            && compressor.option("inline")
+            && !self.is_expr_pure(compressor)
+            && (exp === fn || safe_from_strict_mode(fn, compressor));
         if (can_inline && stat instanceof AST_Return) {
             var value = stat.value;
             if (exp === fn
@@ -11142,9 +11219,15 @@ Compressor.prototype.compress = function(node) {
                 && assign instanceof AST_Assign
                 && assign.operator == "="
                 && self.left.equivalent_to(assign.left)) {
-                self.right = assign.right;
-                assign.right = self;
-                return assign;
+                return make_node(AST_Assign, self, {
+                    operator: "=",
+                    left: assign.left,
+                    right: make_node(AST_Binary, self, {
+                        operator: self.operator,
+                        left: self.left,
+                        right: assign.right,
+                    }),
+                }).optimize(compressor);
             }
         }
         if (compressor.option("comparisons")) switch (self.operator) {
@@ -11809,8 +11892,9 @@ Compressor.prototype.compress = function(node) {
                     } else if (fixed.name && fixed.name.definition() !== def) {
                         single_use = false;
                     } else if (fixed.parent_scope !== self.scope || is_funarg(def)) {
-                        single_use = fixed.is_constant_expression(self.scope);
-                        if (single_use == "f") {
+                        if (!safe_from_strict_mode(fixed, compressor)) {
+                            single_use = false;
+                        } else if ((single_use = fixed.is_constant_expression(self.scope)) == "f") {
                             var scope = self.scope;
                             do {
                                 if (scope instanceof AST_LambdaDefinition || scope instanceof AST_LambdaExpression) {
@@ -13382,7 +13466,7 @@ Compressor.prototype.compress = function(node) {
             });
             var body = [];
             fn.variables.each(function(def, name) {
-                if (name == "arguments") return;
+                if (!arrow && name == "arguments" && def.orig.length == 1) return;
                 names.set(name, true);
                 scope.enclosed.push(def);
                 scope.variables.set(name, def);

lib/minify.js

@@ -81,13 +81,14 @@ function minify(files, options) {
             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,
@@ -101,6 +102,7 @@ function minify(files, options) {
         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" ]);

lib/parse.js

@@ -237,8 +237,7 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
         newline_before  : false,
         regex_allowed   : false,
         comments_before : [],
-        directives      : {},
-        directive_stack : [],
+        directives      : Object.create(null),
         read_template   : with_eof_error("Unterminated template literal", function(strings) {
             var s = "";
             for (;;) {
@@ -635,24 +634,19 @@ function tokenizer($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;
@@ -699,6 +693,7 @@ function parse($TEXT, options) {
         expression     : false,
         filename       : null,
         html5_comments : true,
+        module         : false,
         shebang        : true,
         strict         : false,
         toplevel       : null,
@@ -1340,8 +1335,6 @@ function parse($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", "{")) {
@@ -1352,8 +1345,6 @@ function parse($TEXT, options) {
             handle_regexp();
             value = maybe_assign();
         }
-        var is_strict = S.input.has_directive("use strict");
-        S.input.pop_directives_stack();
         --S.in_function;
         S.in_loop = loop;
         S.labels = labels;
@@ -1367,7 +1358,7 @@ function parse($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;
     }
 
@@ -1412,7 +1403,7 @@ function parse($TEXT, options) {
             name: name,
             argnames: argnames,
             rest: argnames.rest || null,
-            body: body
+            body: body,
         });
         if (is_strict) {
             if (name) strict_verify_symbol(name);
@@ -2550,6 +2541,7 @@ function parse($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());

lib/scope.js

@@ -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() {
@@ -469,6 +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,
     }));
@@ -620,14 +622,10 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options) {
     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) {
@@ -673,6 +671,7 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options) {
                 }));
             }
             to_mangle.forEach(mangle);
+            if (node instanceof AST_LabeledStatement && !(options.v8 && in_label(tw))) lname = save_nesting;
             return true;
         }
         if (node instanceof AST_Label) {

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": "3.15.4",
+  "version": "3.16.0",
   "engines": {
     "node": ">=0.8.0"
   },

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);
@@ -98,7 +96,7 @@ 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 }),
         }));
     }
 
@@ -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;
                         }));

test/compress/arrows.js

@@ -1018,3 +1018,91 @@ issue_5356: {
     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"
+}

test/compress/awaits.js

@@ -1748,8 +1748,8 @@ issue_4454_2: {
     expect: {
         function f(a) {
             (async function(c = console.log(a)) {})();
-            var a = 42..toString();
-            console.log(a);
+            var b = 42..toString();
+            console.log(b);
         }
         f("PASS");
     }
@@ -2427,80 +2427,6 @@ issue_5023_2: {
     node_version: ">=8"
 }
 
-issue_5032_normal: {
-    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_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_5034: {
     options = {
         functions: true,
@@ -2959,3 +2885,79 @@ issue_5305_3: {
     expect_stdout: "PASS"
     node_version: ">=8"
 }
+
+issue_5456: {
+    options = {
+        inline: true,
+        merge_vars: true,
+    }
+    input: {
+        var a = true;
+        (function() {
+            (function(b, c) {
+                var d = async function() {
+                    c = await 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 = async function() {
+                c = await 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: ">=8"
+}
+
+issue_5478: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        A = {
+            get then() {
+                a = "FAIL";
+            },
+        };
+        var a = "PASS";
+        (async function() {
+            for (var b in "foo")
+                return void A;
+        })();
+        console.log(a);
+    }
+    expect: {
+        A = {
+            get then() {
+                a = "FAIL";
+            },
+        };
+        var a = "PASS";
+        (async function() {
+            for (var b in "foo")
+                return !A;
+        })();
+        console.log(a);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}

test/compress/booleans.js

@@ -762,3 +762,27 @@ issue_5228: {
     }
     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"
+}

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,
@@ -670,6 +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,
@@ -742,6 +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,
@@ -1758,12 +1879,14 @@ issue_4962_1: {
         })(function g() {});
     }
     expect: {
-        (function g() {}),
-        void class {
-            static c = function() {
+        (function() {
+            function f() {
                 while (console.log(typeof g));
-            }();
-        };
+            }
+            (class {
+                static c = f();
+            });
+        })(function g() {});
     }
     expect_stdout: "undefined"
     node_version: ">=12"
@@ -1796,6 +1919,37 @@ issue_4962_1_strict: {
     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 class {
+            static c = function() {
+                "use strict";
+                while (console.log(typeof g));
+            }();
+        };
+    }
+    expect_stdout: "undefined"
+    node_version: ">=12"
+}
+
 issue_4962_2: {
     options = {
         ie: true,
@@ -1815,8 +1969,11 @@ issue_4962_2: {
     }
     expect: {
         console.log(function f() {}(function g() {
+            function h() {
+                f;
+            }
             (class {
-                static c = f;
+                static c = h();
             });
         }));
     }
@@ -1852,6 +2009,69 @@ issue_4962_2_strict: {
     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,
@@ -2541,7 +2761,7 @@ issue_5387: {
     node_version: ">=4"
 }
 
-issue_5389: {
+issue_5389_1: {
     options = {
         collapse_vars: true,
         toplevel: true,
@@ -2571,3 +2791,94 @@ issue_5389: {
     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"
+}

test/compress/const.js

@@ -1855,3 +1855,20 @@ issue_5338: {
     }
     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"
+}

test/compress/default-values.js

@@ -2239,3 +2239,226 @@ issue_5407: {
     ]
     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"
+}

test/compress/destructured.js

@@ -1848,8 +1848,8 @@ issue_4294: {
             }) {}({
                 [a]: 0,
             });
-            var a = A;
-            console.log(a);
+            var b = A;
+            console.log(b);
         })();
     }
     expect_stdout: "PASS"
@@ -3020,6 +3020,7 @@ issue_5074_method_pure_getters: {
 issue_5085_1: {
     options = {
         evaluate: true,
+        passes: 2,
         reduce_vars: true,
         toplevel: true,
         unsafe: true,
@@ -3032,8 +3033,7 @@ issue_5085_1: {
     }
     expect: {
         var a = "PASS";
-        var b = [ 42 ][0];
-        b;
+        42;
         console.log(a);
     }
     expect_stdout: "PASS"
@@ -3043,6 +3043,7 @@ issue_5085_1: {
 issue_5085_2: {
     options = {
         evaluate: true,
+        passes: 2,
         reduce_vars: true,
         side_effects: true,
         unsafe: true,
@@ -3059,7 +3060,7 @@ issue_5085_2: {
     expect: {
         var a = "PASS";
         (function(b) {
-            b = [ 42 ][0];
+            0;
         })();
         console.log(a);
     }
@@ -3400,7 +3401,7 @@ issue_5222: {
     node_version: ">=6"
 }
 
-issue_5288: {
+issue_5288_1: {
     options = {
         conditionals: true,
         inline: true,
@@ -3420,7 +3421,37 @@ issue_5288: {
         }() ]));
     }
     expect: {
-        while (console ? console.log("PASS") : 0, void 0);
+        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"
@@ -3535,3 +3566,83 @@ issue_5405_2: {
     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"
+}

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;
+    }
+}

test/compress/functions.js

@@ -8398,3 +8398,251 @@ issue_5409: {
     }
     expect_stdout: "undefined"
 }
+
+mixed_mode_inline_1: {
+    options = {
+        directives: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            return this;
+        }
+        console.log(function() {
+            return f();
+        }() ? "PASS" : "FAIL");
+    }
+    expect: {
+        console.log(function() {
+            return this;
+        }() ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+}
+
+mixed_mode_inline_1_strict: {
+    options = {
+        directives: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        function f() {
+            return this;
+        }
+        console.log(function() {
+            return f();
+        }() ? "FAIL" : "PASS");
+    }
+    expect: {
+        "use strict";
+        console.log(function() {
+            return this;
+        }() ? "FAIL" : "PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+mixed_mode_inline_2: {
+    options = {
+        directives: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            "use strict";
+            return this;
+        }
+        console.log(function() {
+            return f();
+        }() ? "FAIL" : "PASS");
+    }
+    expect: {
+        console.log(function() {
+            "use strict";
+            return this;
+        }() ? "FAIL" : "PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+mixed_mode_inline_2_strict: {
+    options = {
+        directives: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        function f() {
+            "use strict";
+            return this;
+        }
+        console.log(function() {
+            return f();
+        }() ? "FAIL" : "PASS");
+    }
+    expect: {
+        "use strict";
+        console.log(function() {
+            return this;
+        }() ? "FAIL" : "PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+mixed_mode_inline_3: {
+    options = {
+        directives: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            return this;
+        }
+        console.log(function() {
+            "use strict";
+            return f();
+        }() ? "PASS" : "FAIL");
+    }
+    expect: {
+        function f() {
+            return this;
+        }
+        console.log(function() {
+            "use strict";
+            return f();
+        }() ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+}
+
+mixed_mode_inline_3_strict: {
+    options = {
+        directives: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        function f() {
+            return this;
+        }
+        console.log(function() {
+            "use strict";
+            return f();
+        }() ? "FAIL" : "PASS");
+    }
+    expect: {
+        "use strict";
+        console.log(function() {
+            return this;
+        }() ? "FAIL" : "PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+mixed_mode_inline_4: {
+    options = {
+        directives: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            "use strict";
+            return this;
+        }
+        console.log(function() {
+            "use strict";
+            return f();
+        }() ? "FAIL" : "PASS");
+    }
+    expect: {
+        console.log(function() {
+            "use strict";
+            return function() {
+                "use strict";
+                return this;
+            }();
+        }() ? "FAIL" : "PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+mixed_mode_inline_4_strict: {
+    options = {
+        directives: true,
+        inline: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        function f() {
+            "use strict";
+            return this;
+        }
+        console.log(function() {
+            "use strict";
+            return f();
+        }() ? "FAIL" : "PASS");
+    }
+    expect: {
+        "use strict";
+        console.log(function() {
+            return this;
+        }() ? "FAIL" : "PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+module_inline: {
+    options = {
+        inline: true,
+        module: true,
+        reduce_vars: true,
+    }
+    input: {
+        var a = f;
+        function f() {
+            return a;
+        }
+        console.log(f() === a);
+    }
+    expect: {
+        var a = f;
+        function f() {
+            return a;
+        }
+        console.log(a === a);
+    }
+    expect_stdout: "true"
+}

test/compress/hoist_props.js

@@ -1176,3 +1176,30 @@ issue_5182: {
         "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"
+}

test/compress/let.js

@@ -1604,48 +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,
@@ -2020,3 +1978,23 @@ issue_5338: {
     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"
+}

test/compress/merge_vars.js

@@ -3702,3 +3702,146 @@ issue_5182: {
     ]
     node_version: ">=4"
 }
+
+issue_5420: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        do {
+            var a = "FAIL 1";
+            a && a.p;
+            a = "FAIL 2";
+            try {
+                continue;
+            } catch (e) {}
+            var b = "FAIL 3";
+        } while (console.log(b || "PASS"));
+    }
+    expect: {
+        do {
+            var a = "FAIL 1";
+            a && a.p;
+            a = "FAIL 2";
+            try {
+                continue;
+            } catch (e) {}
+            var b = "FAIL 3";
+        } while (console.log(b || "PASS"));
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5451: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        A = 1;
+        var a = 1, b;
+        console.log(function f() {
+            return a-- && f(b = A, b);
+        }());
+    }
+    expect: {
+        A = 1;
+        var a = 1, b;
+        console.log(function f() {
+            return a-- && f(b = A, b);
+        }());
+    }
+    expect_stdout: "0"
+}
+
+issue_5471_1: {
+    options = {
+        conditionals: true,
+        inline: true,
+        merge_vars: true,
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = "FAIL 1";
+        function f(b, c) {
+            function g() {
+                if (console)
+                    return 42;
+                else
+                    c = "FAIL 2";
+            }
+            var d = g();
+            console.log(c || "PASS");
+            var e = function h() {
+                while (b && e);
+            }();
+        }
+        f(a++) && a;
+    }
+    expect: {
+        var a = "FAIL 1";
+        var b, c, e;
+        b = +a,
+        function() {
+            if (console)
+                return;
+            c = "FAIL 2";
+        }(),
+        console.log(c || "PASS"),
+        e = function() {
+            while (b && e);
+        }();
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5471_2: {
+    options = {
+        conditionals: true,
+        evaluate: true,
+        inline: true,
+        merge_vars: true,
+        reduce_vars: true,
+        sequences: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a = "FAIL 1";
+        function f(b, c) {
+            function g() {
+                if (console)
+                    return 42;
+                else
+                    c = "FAIL 2";
+            }
+            var d = g();
+            console.log(c || "PASS");
+            var e = function h() {
+                while (b && e);
+            }();
+        }
+        f(a++) && a;
+    }
+    expect: {
+        var a = "FAIL 1";
+        var b, c, e;
+        b = +a,
+        function() {
+            if (console)
+                return;
+            c = "FAIL 2";
+        }(),
+        console.log(c || "PASS"),
+        e = function() {
+            while (b && e);
+        }(),
+        void 0;
+    }
+    expect_stdout: "PASS"
+}

test/compress/reduce_vars.js

@@ -7861,3 +7861,38 @@ issue_5324: {
     }
     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"
+}

test/compress/varify.js

@@ -111,7 +111,7 @@ hoist_props_const: {
         }
     }
     expect: {
-        var o = 0, o_p = "PASS";
+        var o, o_p = "PASS";
         console.log(o_p);
     }
     expect_stdout: "PASS"

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"
+}

test/compress/yields.js

@@ -978,8 +978,8 @@ issue_4454_2: {
     expect: {
         function f(a) {
             (function*(c = console.log(a)) {})();
-            var a = 42..toString();
-            console.log(a);
+            var b = 42..toString();
+            console.log(b);
         }
         f("PASS");
     }
@@ -1267,80 +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(a) {
-            var a = log(a), c = a;
-            log(a);
-            log(c);
-        }
-        f("PASS").next();
-    }
-    expect_stdout: [
-        "PASS",
-        "PASS",
-        "PASS",
-    ]
-    node_version: ">=4"
-}
-
-issue_5032_webkit: {
-    options = {
-        merge_vars: true,
-        webkit: true,
-    }
-    input: {
-        function log(value) {
-            console.log(value);
-            return value;
-        }
-        function *f(a) {
-            var b = log(a), c = b;
-            log(b);
-            log(c);
-        }
-        f("PASS").next();
-    }
-    expect: {
-        function log(value) {
-            console.log(value);
-            return value;
-        }
-        function *f(a) {
-            var b = log(a), c = b;
-            log(b);
-            log(c);
-        }
-        f("PASS").next();
-    }
-    expect_stdout: [
-        "PASS",
-        "PASS",
-        "PASS",
-    ]
-    node_version: ">=4"
-}
-
 issue_5034: {
     options = {
         functions: true,
@@ -1525,3 +1451,67 @@ issue_5385_2: {
     ]
     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"
+}

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));

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);
+}());

test/mocha/cli.js

@@ -928,6 +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() {",

test/reduce.js

@@ -210,10 +210,10 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
             }
             if (node.expression instanceof U.AST_Function) {
                 // hoist and return expressions from the IIFE function expression
-                var seq = [];
+                var scope = tt.find_parent(U.AST_Scope), seq = [];
                 node.expression.body.forEach(function(node) {
                     var expr = node instanceof U.AST_Exit ? node.value : node.body;
-                    if (expr instanceof U.AST_Node && !U.is_statement(expr) && can_hoist(expr)) {
+                    if (expr instanceof U.AST_Node && !U.is_statement(expr) && can_hoist(expr, scope)) {
                         // collect expressions from each statement's body
                         seq.push(expr);
                     }
@@ -264,11 +264,12 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                 CHANGED = true;
                 return List.skip;
               default:
-                if (!has_exit(node) && can_hoist(node)) {
+                if (can_hoist(node, tt.find_parent(U.AST_Scope))) {
                     // hoist function declaration body
                     var body = node.body;
                     node.body = [];
-                    body.push(node); // retain function with empty body to be dropped later
+                    // retain function with empty body to be dropped later
+                    body.push(node);
                     CHANGED = true;
                     return List.splice(body);
                 }
@@ -382,7 +383,7 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
             if (node.body instanceof U.AST_Call && node.body.expression instanceof U.AST_Function) {
                 // hoist simple statement IIFE function expression body
                 node.start._permute++;
-                if (!has_exit(node.body.expression) && can_hoist(node.body.expression)) {
+                if (can_hoist(node.body.expression, tt.find_parent(U.AST_Scope))) {
                     CHANGED = true;
                     return List.splice(node.body.expression.body);
                 }
@@ -647,21 +648,6 @@ function trim_trailing_whitespace(value) {
     return ("" + value).replace(/\s+$/, "");
 }
 
-function has_exit(fn) {
-    var found = false;
-    var tw = new U.TreeWalker(function(node) {
-        if (found) return found;
-        if (node instanceof U.AST_Exit) {
-            return found = true;
-        }
-        if (node instanceof U.AST_Scope && node !== fn) {
-            return true; // don't descend into nested functions
-        }
-    });
-    fn.walk(tw);
-    return found;
-}
-
 function has_loopcontrol(body, loop, label) {
     var found = false;
     var tw = new U.TreeWalker(function(node) {
@@ -676,17 +662,31 @@ function has_loopcontrol(body, loop, label) {
     return found;
 }
 
-function can_hoist(body) {
+function can_hoist(body, scope) {
     var found = false;
-    body.walk(new U.TreeWalker(function(node) {
+    var tw = new U.TreeWalker(function(node) {
         if (found) return true;
+        if (node instanceof U.AST_Exit) return found = true;
         if (node instanceof U.AST_NewTarget) return found = true;
         if (node instanceof U.AST_Scope) {
             if (node === body) return;
+            if (node instanceof U.AST_Arrow || node instanceof U.AST_AsyncArrow) node.argnames.forEach(function(sym) {
+                sym.walk(tw);
+            });
+            // don't descend into nested functions
             return true;
         }
         if (node instanceof U.AST_Super) return found = true;
-    }));
+        if (node instanceof U.AST_SymbolDeclaration || node instanceof U.AST_SymbolRef) switch (node.name) {
+          case "await":
+            if (/^Async/.test(scope.TYPE)) return found = true;
+            return;
+          case "yield":
+            if (/Generator/.test(scope.TYPE)) return found = true;
+            return;
+        }
+    });
+    body.walk(tw);
     return !found;
 }
 

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 \

test/sandbox.js

@@ -52,8 +52,11 @@ 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, has_default = "", 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;
@@ -78,7 +81,7 @@ exports.patch_module_statements = function(code) {
         return "";
     });
     imports.push("");
-    return has_default + imports.join("\n") + code;
+    return strict_mode + has_default + imports.join("\n") + code;
 };
 
 function is_error(result) {

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;
 }({
@@ -1805,7 +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";
@@ -1824,9 +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;
@@ -2031,7 +2037,7 @@ function isBannedKeyword(name) {
       case "let":
         return in_class;
       case "await":
-        return async !== false;
+        return async || in_class && bug_class_static_await;
       case "yield":
         return generator || in_class;
     }
@@ -2110,7 +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 {
@@ -2147,7 +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);
@@ -2175,7 +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);
@@ -2204,7 +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();
@@ -2213,15 +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) {
@@ -2318,20 +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) {
@@ -2345,6 +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,
@@ -2382,7 +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({
@@ -2394,27 +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 = {
@@ -2426,22 +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 = {};
@@ -2450,7 +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");
@@ -2458,7 +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("//=============================================================");
@@ -2480,19 +2505,20 @@ 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_result.message == "Script execution aborted.") ok = true;
+            if (!ok && uglify_erred && uglify_result.message == "Script execution aborted.") ok = true;
             // handle difference caused by time-outs
             if (!ok) {
-                if (errored && is_error_timeout(original_result)) {
-                    if (is_error_timeout(uglify_result)) {
+                if (original_erred && is_error_timeout(original_result)) {
+                    if (uglify_erred && is_error_timeout(uglify_result)) {
                         // ignore difference in error message
                         ok = true;
                     } else {
@@ -2500,21 +2526,23 @@ for (var round = 1; round <= num_iterations; round++) {
                         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 (is_error_timeout(uglify_result)) {
+                } else if (uglify_erred && is_error_timeout(uglify_result)) {
                     // ignore spurious time-outs
                     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 && uglify_result.name != "SyntaxError" && original_result.name != "SyntaxError") {
+            if (!ok && !toplevel) {
+                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) {
@@ -2522,46 +2550,33 @@ for (var round = 1; round <= num_iterations; round++) {
                     ok = sandbox.same_stdout(fuzzy_result, uglify_result);
                 }
             }
+            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
-            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);
-                if (/^(Syntax|Type)Error$/.test(uglify_result.name)) {
-                    ok = typeof original_strict != "string";
-                } else {
-                    ok = sandbox.same_stdout(original_strict, uglify_result);
-                }
-            }
+                || 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
-            if (!ok && errored && /\bimport\b/.test(original_code)) {
-                if (is_error_redeclaration(uglify_result) && is_error_redeclaration(original_result)) ok = true;
-            }
+                || /\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) {
@@ -2573,7 +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)) {