support destructured literals (#4278)

README.md

@@ -906,6 +906,8 @@ can pass additional arguments that control the code output:
 
 - `shebang` (default `true`) -- preserve shebang `#!` in preamble (bash scripts)
 
+- `v8` (default `false`) -- enable workarounds for Chrome & Node.js bugs
+
 - `webkit` (default `false`) -- enable workarounds for WebKit bugs.
   PhantomJS users should set this option to `true`.
 
@@ -1138,7 +1140,7 @@ To enable fast minify mode with the API use:
 UglifyJS.minify(code, { compress: false, mangle: true });
 ```
 
-#### Source maps and debugging
+### Source maps and debugging
 
 Various `compress` transforms that simplify, rearrange, inline and remove code
 are known to have an adverse effect on debugging with source maps. This is
@@ -1150,6 +1152,10 @@ disable the Uglify `compress` option and just use `mangle`.
 
 To allow for better optimizations, the compiler makes various assumptions:
 
+- The code does not rely on preserving its runtime performance characteristics.
+  Typically uglified code will run faster due to less instructions and easier
+  inlining, but may be slower on rare occasions for a specific platform, e.g.
+  see [`reduce_funcs`](#compress-options).
 - `.toString()` and `.valueOf()` don't have side effects, and for built-in
   objects they have not been overridden.
 - `undefined`, `NaN` and `Infinity` have not been externally redefined.
@@ -1177,3 +1183,7 @@ To allow for better optimizations, the compiler makes various assumptions:
   top.B = "PASS";
   console.log(B);
   ```
+- Use of `arguments` alongside destructuring as function parameters, e.g.
+  `function({}, arguments) {}` will result in `SyntaxError` in earlier versions
+  of Chrome and Node.js - UglifyJS may modify the input which in turn may
+  suppress those errors.

lib/ast.js

@@ -414,8 +414,12 @@ var AST_ForIn = DEFNODE("ForIn", "init object", {
     _validate: function() {
         if (this.init instanceof AST_Definitions) {
             if (this.init.definitions.length != 1) throw new Error("init must have single declaration");
-        } else if (!(this.init instanceof AST_PropAccess || this.init instanceof AST_SymbolRef)) {
-            throw new Error("init must be assignable");
+        } else {
+            validate_destructured(this.init, function(node) {
+                if (!(node instanceof AST_PropAccess || node instanceof AST_SymbolRef)) {
+                    throw new Error("init must be assignable: " + node.TYPE);
+                }
+            });
         }
         must_be_expression(this, "object");
     },
@@ -496,12 +500,26 @@ var AST_Toplevel = DEFNODE("Toplevel", "globals", {
     }
 }, AST_Scope);
 
-var AST_Lambda = DEFNODE("Lambda", "name argnames uses_arguments length_read", {
+var AST_Lambda = DEFNODE("Lambda", "name argnames length_read uses_arguments", {
     $documentation: "Base class for functions",
     $propdoc: {
         name: "[AST_SymbolDeclaration?] the name of this function",
-        argnames: "[AST_SymbolFunarg*] array of function arguments",
-        uses_arguments: "[boolean/S] tells whether this function accesses the arguments array"
+        argnames: "[(AST_Destructured|AST_SymbolFunarg)*] array of function arguments and/or destructured literals",
+        uses_arguments: "[boolean/S] tells whether this function accesses the arguments array",
+    },
+    each_argname: function(visit) {
+        var tw = new TreeWalker(function(node) {
+            if (node instanceof AST_DestructuredObject) {
+                node.properties.forEach(function(prop) {
+                    prop.value.walk(tw);
+                });
+                return true;
+            }
+            if (node instanceof AST_SymbolFunarg) visit(node);
+        });
+        this.argnames.forEach(function(argname) {
+            argname.walk(tw);
+        });
     },
     walk: function(visitor) {
         var node = this;
@@ -515,8 +533,10 @@ var AST_Lambda = DEFNODE("Lambda", "name argnames uses_arguments length_read", {
     },
     _validate: function() {
         this.argnames.forEach(function(node) {
+            validate_destructured(node, function(node) {
                 if (!(node instanceof AST_SymbolFunarg)) throw new Error("argnames must be AST_SymbolFunarg[]");
             });
+        });
     },
 }, AST_Scope);
 
@@ -748,8 +768,10 @@ var AST_Const = DEFNODE("Const", null, {
     _validate: function() {
         this.definitions.forEach(function(node) {
             if (!(node instanceof AST_VarDef)) throw new Error("definitions must be AST_VarDef[]");
-            if (!(node.name instanceof AST_SymbolConst)) throw new Error("name must be AST_SymbolConst");
-            must_be_expression(node, "value");
+            validate_destructured(node.name, function(node) {
+                if (!(node instanceof AST_SymbolConst)) throw new Error("name must be AST_SymbolConst");
+            });
+            if (node.value != null) must_be_expression(node, "value");
         });
     },
 }, AST_Definitions);
@@ -759,7 +781,9 @@ var AST_Let = DEFNODE("Let", null, {
     _validate: function() {
         this.definitions.forEach(function(node) {
             if (!(node instanceof AST_VarDef)) throw new Error("definitions must be AST_VarDef[]");
-            if (!(node.name instanceof AST_SymbolLet)) throw new Error("name must be AST_SymbolLet");
+            validate_destructured(node.name, function(node) {
+                if (!(node instanceof AST_SymbolLet)) throw new Error("name must be AST_SymbolLet");
+            });
             if (node.value != null) must_be_expression(node, "value");
         });
     },
@@ -770,7 +794,9 @@ var AST_Var = DEFNODE("Var", null, {
     _validate: function() {
         this.definitions.forEach(function(node) {
             if (!(node instanceof AST_VarDef)) throw new Error("definitions must be AST_VarDef[]");
-            if (!(node.name instanceof AST_SymbolVar)) throw new Error("name must be AST_SymbolVar");
+            validate_destructured(node.name, function(node) {
+                if (!(node instanceof AST_SymbolVar)) throw new Error("name must be AST_SymbolVar");
+            });
             if (node.value != null) must_be_expression(node, "value");
         });
     },
@@ -969,6 +995,14 @@ var AST_Assign = DEFNODE("Assign", null, {
     $documentation: "An assignment expression — `a = b + 5`",
     _validate: function() {
         if (this.operator.indexOf("=") < 0) throw new Error('operator must contain "="');
+        if (this.left instanceof AST_Destructured) {
+            if (this.operator != "=") throw new Error("invalid destructuring operator: " + this.operator);
+            validate_destructured(this.left, function(node) {
+                if (!(node instanceof AST_PropAccess || node instanceof AST_SymbolRef)) {
+                    throw new Error("left must be assignable: " + node.TYPE);
+                }
+            });
+        }
     },
 }, AST_Binary);
 
@@ -992,6 +1026,77 @@ var AST_Array = DEFNODE("Array", "elements", {
     },
 });
 
+var AST_Destructured = DEFNODE("Destructured", null, {
+    $documentation: "Base class for destructured literal",
+});
+
+function validate_destructured(node, check) {
+    if (node instanceof AST_DestructuredArray) return node.elements.forEach(function(node) {
+        if (!(node instanceof AST_Hole)) validate_destructured(node, check);
+    });
+    if (node instanceof AST_DestructuredObject) return node.properties.forEach(function(prop) {
+        validate_destructured(prop.value, check);
+    });
+    check(node);
+}
+
+var AST_DestructuredArray = DEFNODE("DestructuredArray", "elements", {
+    $documentation: "A destructured array literal",
+    $propdoc: {
+        elements: "[AST_Node*] array of elements",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.elements.forEach(function(element) {
+                element.walk(visitor);
+            });
+        });
+    },
+}, AST_Destructured);
+
+var AST_DestructuredKeyVal = DEFNODE("DestructuredKeyVal", "key value", {
+    $documentation: "A key: value destructured property",
+    $propdoc: {
+        key: "[string|AST_Node] property name.  For computed property this is an AST_Node.",
+        value: "[AST_Node] property value",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            if (node.key instanceof AST_Node) node.key.walk(visitor);
+            node.value.walk(visitor);
+        });
+    },
+    _validate: function() {
+        if (typeof this.key != "string") {
+            if (!(this.key instanceof AST_Node)) throw new Error("key must be string or AST_Node");
+            must_be_expression(this, "key");
+        }
+        must_be_expression(this, "value");
+    },
+});
+
+var AST_DestructuredObject = DEFNODE("DestructuredObject", "properties", {
+    $documentation: "A destructured object literal",
+    $propdoc: {
+        properties: "[AST_DestructuredKeyVal*] array of properties",
+    },
+    walk: function(visitor) {
+        var node = this;
+        visitor.visit(node, function() {
+            node.properties.forEach(function(prop) {
+                prop.walk(visitor);
+            });
+        });
+    },
+    _validate: function() {
+        this.properties.forEach(function(node) {
+            if (!(node instanceof AST_DestructuredKeyVal)) throw new Error("properties must be AST_DestructuredKeyVal[]");
+        });
+    },
+}, AST_Destructured);
+
 var AST_Object = DEFNODE("Object", "properties", {
     $documentation: "An object literal",
     $propdoc: {

lib/output.js

@@ -69,6 +69,7 @@ function OutputStream(options) {
         semicolons       : true,
         shebang          : true,
         source_map       : null,
+        v8               : false,
         webkit           : false,
         width            : 80,
         wrap_iife        : false,
@@ -499,11 +500,11 @@ function OutputStream(options) {
                 }
             }
             if (/comment[134]/.test(c.type)) {
-                print("//" + c.value.replace(/[@#]__PURE__/g, ' ') + "\n");
+                print("//" + c.value.replace(/[@#]__PURE__/g, " ") + "\n");
                 indent();
                 last_nlb = true;
             } else if (c.type == "comment2") {
-                print("/*" + c.value.replace(/[@#]__PURE__/g, ' ') + "*/");
+                print("/*" + c.value.replace(/[@#]__PURE__/g, " ") + "*/");
                 last_nlb = false;
             }
         });
@@ -557,10 +558,10 @@ function OutputStream(options) {
                 space();
             }
             if (/comment[134]/.test(c.type)) {
-                print("//" + c.value.replace(/[@#]__PURE__/g, ' '));
+                print("//" + c.value.replace(/[@#]__PURE__/g, " "));
                 need_newline_indented = true;
             } else if (c.type == "comment2") {
-                print("/*" + c.value.replace(/[@#]__PURE__/g, ' ') + "*/");
+                print("/*" + c.value.replace(/[@#]__PURE__/g, " ") + "*/");
                 need_space = true;
             }
         });
@@ -610,7 +611,7 @@ function OutputStream(options) {
         },
         parent          : function(n) {
             return stack[stack.length - 2 - (n || 0)];
-        }
+        },
     };
 }
 
@@ -652,14 +653,8 @@ function OutputStream(options) {
     /* -----[ PARENTHESES ]----- */
 
     function PARENS(nodetype, func) {
-        if (Array.isArray(nodetype)) {
-            nodetype.forEach(function(nodetype) {
-                PARENS(nodetype, func);
-            });
-        } else {
         nodetype.DEFMETHOD("needs_parens", func);
     }
-    }
 
     PARENS(AST_Node, return_false);
 
@@ -667,11 +662,11 @@ function OutputStream(options) {
     // the first token to appear in a statement.
     PARENS(AST_Function, function(output) {
         if (!output.has_parens() && first_in_statement(output)) return true;
-        if (output.option('webkit')) {
+        if (output.option("webkit")) {
             var p = output.parent();
             if (p instanceof AST_PropAccess && p.expression === this) return true;
         }
-        if (output.option('wrap_iife')) {
+        if (output.option("wrap_iife")) {
             var p = output.parent();
             if (p instanceof AST_Call && p.expression === this) return true;
         }
@@ -679,9 +674,10 @@ function OutputStream(options) {
 
     // same goes for an object literal, because otherwise it would be
     // interpreted as a block of code.
-    PARENS(AST_Object, function(output) {
+    function needs_parens_obj(output) {
         return !output.has_parens() && first_in_statement(output);
-    });
+    }
+    PARENS(AST_Object, needs_parens_obj);
 
     PARENS(AST_Unary, function(output) {
         var p = output.parent();
@@ -701,6 +697,7 @@ function OutputStream(options) {
             || p instanceof AST_Conditional
             // { [(1, 2)]: 3 }[2] ==> 3
             // { foo: (1, 2) }.foo ==> 2
+            || p instanceof AST_DestructuredKeyVal
             || p instanceof AST_ObjectProperty
             // (1, {foo:2}).foo or (1, {foo:2})["foo"] ==> 2
             || p instanceof AST_PropAccess && p.expression === this
@@ -747,7 +744,7 @@ function OutputStream(options) {
         var p = output.parent();
         if (p instanceof AST_New) return p.expression === this;
         // https://bugs.webkit.org/show_bug.cgi?id=123506
-        if (output.option('webkit')) {
+        if (output.option("webkit")) {
             var g = output.parent(1);
             return this.expression instanceof AST_Function
                 && p instanceof AST_PropAccess
@@ -776,18 +773,29 @@ function OutputStream(options) {
         }
     });
 
-    PARENS([ AST_Assign, AST_Conditional ], function(output) {
+    function needs_parens_assign_cond(self, output) {
         var p = output.parent();
         // 1 + (a = 2) + 3 → 6, side effect setting a = 2
         if (p instanceof AST_Binary) return !(p instanceof AST_Assign);
         // (a = func)() —or— new (a = Object)()
-        if (p instanceof AST_Call) return p.expression === this;
+        if (p instanceof AST_Call) return p.expression === self;
         // (a = foo) ? bar : baz
-        if (p instanceof AST_Conditional) return p.condition === this;
+        if (p instanceof AST_Conditional) return p.condition === self;
         // (a = foo)["prop"] —or— (a = foo).prop
-        if (p instanceof AST_PropAccess) return p.expression === this;
+        if (p instanceof AST_PropAccess) return p.expression === self;
         // !(a = false) → true
         if (p instanceof AST_Unary) return true;
+    }
+    PARENS(AST_Assign, function(output) {
+        if (needs_parens_assign_cond(this, output)) return true;
+        //  v8 parser bug   =>     workaround
+        // f([1], [a] = []) => f([1], ([a] = []))
+        if (output.option("v8")) return this.left instanceof AST_Destructured;
+        // ({ p: a } = o);
+        if (this.left instanceof AST_DestructuredObject) return needs_parens_obj(output);
+    });
+    PARENS(AST_Conditional, function(output) {
+        return needs_parens_assign_cond(this, output);
     });
 
     /* -----[ PRINTERS ]----- */
@@ -1274,6 +1282,38 @@ function OutputStream(options) {
             output.space();
         } : noop);
     });
+    DEFPRINT(AST_DestructuredArray, function(output) {
+        var a = this.elements, len = a.length;
+        output.with_square(len > 0 ? function() {
+            output.space();
+            a.forEach(function(exp, i) {
+                if (i) output.comma();
+                exp.print(output);
+                // If the final element is a hole, we need to make sure it
+                // doesn't look like a trailing comma, by inserting an actual
+                // trailing comma.
+                if (i === len - 1 && exp instanceof AST_Hole)
+                  output.comma();
+            });
+            output.space();
+        } : noop);
+    });
+    DEFPRINT(AST_DestructuredKeyVal, print_key_value);
+    DEFPRINT(AST_DestructuredObject, function(output) {
+        var props = this.properties;
+        if (props.length > 0) output.with_block(function() {
+            props.forEach(function(prop, i) {
+                if (i) {
+                    output.print(",");
+                    output.newline();
+                }
+                output.indent();
+                prop.print(output);
+            });
+            output.newline();
+        });
+        else print_braced_empty(this, output);
+    });
     DEFPRINT(AST_Object, function(output) {
         var props = this.properties;
         if (props.length > 0) output.with_block(function() {
@@ -1314,12 +1354,13 @@ function OutputStream(options) {
         }
     }
 
-    DEFPRINT(AST_ObjectKeyVal, function(output) {
+    function print_key_value(output) {
         var self = this;
         print_property_key(self, output);
         output.colon();
         self.value.print(output);
-    });
+    }
+    DEFPRINT(AST_ObjectKeyVal, print_key_value);
     function print_accessor(type) {
         return function(output) {
             var self = this;
@@ -1483,6 +1524,7 @@ function OutputStream(options) {
         AST_Constant,
         AST_Debugger,
         AST_Definitions,
+        AST_Destructured,
         AST_Finally,
         AST_Jump,
         AST_Lambda,
@@ -1497,7 +1539,7 @@ function OutputStream(options) {
         output.add_mapping(this.start);
     });
 
-    DEFMAP([ AST_ObjectProperty ], function(output) {
+    DEFMAP([ AST_DestructuredKeyVal, AST_ObjectProperty ], function(output) {
         if (typeof this.key == "string") output.add_mapping(this.start, this.key);
     });
 })();

lib/parse.js

@@ -973,14 +973,16 @@ function parse($TEXT, options) {
         if (!is("punc", ";")) {
             init = is("keyword", "const")
                 ? (next(), const_(true))
+                : is("keyword", "let")
+                ? (next(), let_(true))
                 : is("keyword", "var")
                 ? (next(), var_(true))
                 : expression(true, true);
             if (is("operator", "in")) {
-                if (init instanceof AST_Var) {
+                if (init instanceof AST_Definitions) {
                     if (init.definitions.length > 1)
                         croak("Only one variable declaration allowed in for..in loop", init.start.line, init.start.col, init.start.pos);
-                } else if (!is_assignable(init)) {
+                } else if (!(is_assignable(init) || (init = to_destructured(init)) instanceof AST_Destructured)) {
                     croak("Invalid left-hand side in for..in loop", init.start.line, init.start.col, init.start.pos);
                 }
                 next();
@@ -1025,7 +1027,7 @@ function parse($TEXT, options) {
         var argnames = [];
         for (var first = true; !is("punc", ")");) {
             if (first) first = false; else expect(",");
-            argnames.push(as_symbol(AST_SymbolFunarg));
+            argnames.push(maybe_destructured(AST_SymbolFunarg));
         }
         next();
         var loop = S.in_loop;
@@ -1146,16 +1148,16 @@ function parse($TEXT, options) {
         });
     }
 
-    function vardefs(type, no_in, must_init) {
+    function vardefs(type, no_in) {
         var a = [];
         for (;;) {
             var start = S.token;
-            var name = as_symbol(type);
+            var name = maybe_destructured(type);
             var value = null;
             if (is("operator", "=")) {
                 next();
                 value = expression(false, no_in);
-            } else if (must_init) {
+            } else if (!no_in && (type === AST_SymbolConst || name instanceof AST_Destructured)) {
                 croak("Missing initializer in declaration");
             }
             a.push(new AST_VarDef({
@@ -1174,7 +1176,7 @@ function parse($TEXT, options) {
     var const_ = function(no_in) {
         return new AST_Const({
             start       : prev(),
-            definitions : vardefs(AST_SymbolConst, no_in, true),
+            definitions : vardefs(AST_SymbolConst, no_in),
             end         : prev()
         });
     };
@@ -1306,7 +1308,8 @@ function parse($TEXT, options) {
         unexpected();
     };
 
-    function expr_list(closing, allow_trailing_comma, allow_empty) {
+    function expr_list(closing, allow_trailing_comma, allow_empty, parser) {
+        if (!parser) parser = expression;
         var first = true, a = [];
         while (!is("punc", closing)) {
             if (first) first = false; else expect(",");
@@ -1314,7 +1317,7 @@ function parse($TEXT, options) {
             if (is("punc", ",") && allow_empty) {
                 a.push(new AST_Hole({ start: S.token, end: S.token }));
             } else {
-                a.push(expression(false));
+                a.push(parser());
             }
         }
         next();
@@ -1449,6 +1452,54 @@ function parse($TEXT, options) {
         return sym;
     }
 
+    function maybe_destructured(type) {
+        var start = S.token;
+        if (is("punc", "[")) {
+            next();
+            return new AST_DestructuredArray({
+                start: start,
+                elements: expr_list("]", !options.strict, true, function() {
+                    return maybe_destructured(type);
+                }),
+                end: prev(),
+            });
+        }
+        if (is("punc", "{")) {
+            next();
+            var first = true, a = [];
+            while (!is("punc", "}")) {
+                if (first) first = false; else expect(",");
+                // allow trailing comma
+                if (!options.strict && is("punc", "}")) break;
+                var key_start = S.token;
+                var key = as_property_key();
+                if (!is("punc", ":") && key_start.type == "name") {
+                    a.push(new AST_DestructuredKeyVal({
+                        start: key_start,
+                        key: key,
+                        value: _make_symbol(type, key_start),
+                        end: prev(),
+                    }));
+                    continue;
+                }
+                expect(":");
+                a.push(new AST_DestructuredKeyVal({
+                    start: key_start,
+                    key: key,
+                    value: maybe_destructured(type),
+                    end: prev(),
+                }));
+            }
+            next();
+            return new AST_DestructuredObject({
+                start: start,
+                properties: a,
+                end: prev(),
+            });
+        }
+        return as_symbol(type);
+    }
+
     function mark_pure(call) {
         var start = call.start;
         var comments = start.comments_before;
@@ -1578,11 +1629,43 @@ function parse($TEXT, options) {
         return expr instanceof AST_PropAccess || expr instanceof AST_SymbolRef;
     }
 
+    function to_destructured(node) {
+        if (node instanceof AST_Array) {
+            var elements = node.elements.map(to_destructured);
+            return all(elements, function(node) {
+                return node instanceof AST_Destructured || node instanceof AST_Hole || is_assignable(node);
+            }) ? new AST_DestructuredArray({
+                start: node.start,
+                elements: elements,
+                end: node.end,
+            }) : node;
+        }
+        if (!(node instanceof AST_Object)) return node;
+        var props = [];
+        for (var i = 0; i < node.properties.length; i++) {
+            var prop = node.properties[i];
+            if (!(prop instanceof AST_ObjectKeyVal)) return node;
+            var value = to_destructured(prop.value);
+            if (!(value instanceof AST_Destructured || is_assignable(value))) return node;
+            props.push(new AST_DestructuredKeyVal({
+                start: prop.start,
+                key: prop.key,
+                value: value,
+                end: prop.end,
+            }));
+        }
+        return new AST_DestructuredObject({
+            start: node.start,
+            properties: props,
+            end: node.end,
+        });
+    }
+
     var maybe_assign = function(no_in) {
         var start = S.token;
         var left = maybe_conditional(no_in), val = S.token.value;
         if (is("operator") && ASSIGNMENT[val]) {
-            if (is_assignable(left)) {
+            if (is_assignable(left) || val == "=" && (left = to_destructured(left)) instanceof AST_Destructured) {
                 next();
                 return new AST_Assign({
                     start    : start,

lib/scope.js

@@ -204,7 +204,17 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
 
     // pass 2: find back references and eval
     self.globals = new Dictionary();
+    var in_arg = [];
     var tw = new TreeWalker(function(node) {
+        if (node instanceof AST_Lambda) {
+            in_arg.push(node);
+            node.argnames.forEach(function(argname) {
+                argname.walk(tw);
+            });
+            in_arg.pop();
+            walk_body(node, tw);
+            return true;
+        }
         if (node instanceof AST_LoopControl) {
             if (node.label) node.label.thedef.references.push(node);
             return true;
@@ -212,6 +222,16 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
         if (node instanceof AST_SymbolRef) {
             var name = node.name;
             var sym = node.scope.find_variable(name);
+            for (var i = in_arg.length; i > 0 && sym;) {
+                i = in_arg.lastIndexOf(sym.scope, i - 1);
+                if (i < 0) break;
+                var decl = sym.orig[0];
+                if (decl instanceof AST_SymbolFunarg || decl instanceof AST_SymbolLambda) {
+                    node.in_arg = true;
+                    break;
+                }
+                sym = sym.scope.parent_scope.find_variable(name);
+            }
             if (!sym) {
                 sym = self.def_global(node);
             } else if (name == "arguments" && sym.scope instanceof AST_Lambda) {

lib/transform.js

@@ -160,6 +160,16 @@ TreeTransformer.prototype = new TreeWalker;
     DEF(AST_Array, function(self, tw) {
         self.elements = do_list(self.elements, tw);
     });
+    DEF(AST_DestructuredArray, function(self, tw) {
+        self.elements = do_list(self.elements, tw);
+    });
+    DEF(AST_DestructuredKeyVal, function(self, tw) {
+        if (self.key instanceof AST_Node) self.key = self.key.transform(tw);
+        self.value = self.value.transform(tw);
+    });
+    DEF(AST_DestructuredObject, function(self, tw) {
+        self.properties = do_list(self.properties, tw);
+    });
     DEF(AST_Object, function(self, tw) {
         self.properties = do_list(self.properties, tw);
     });

test/reduce.js

@@ -95,6 +95,7 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
 
             // quick ignores
             if (node instanceof U.AST_Accessor) return;
+            if (node instanceof U.AST_Destructured) return;
             if (node instanceof U.AST_Directive) return;
             if (!in_list && node instanceof U.AST_EmptyStatement) return;
             if (node instanceof U.AST_Label) return;
@@ -114,6 +115,8 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
 
             // ignore lvalues
             if (parent instanceof U.AST_Assign && parent.left === node) return;
+            if (parent instanceof U.AST_Destructured) return;
+            if (parent instanceof U.AST_DestructuredKeyVal && parent.value === node) return;
             if (parent instanceof U.AST_Unary && parent.expression === node) switch (parent.operator) {
               case "++":
               case "--":
@@ -250,13 +253,23 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                 }
             }
             else if (node instanceof U.AST_ForIn) {
-                var expr = [
-                    node.init,
-                    node.object,
-                    node.body,
-                ][ (node.start._permute * steps | 0) % 3 ];
+                var expr;
+                switch ((node.start._permute * steps | 0) % 3) {
+                  case 0:
+                    if (!(node.init instanceof U.AST_Definitions
+                        && node.init.definitions[0].name instanceof U.AST_Destructured)) {
+                        expr = node.init;
+                    }
+                    break;
+                  case 1:
+                    expr = node.object;
+                    break;
+                  case 2:
+                    if (!has_loopcontrol(node.body, node, parent)) expr = node.body;
+                    break;
+                }
                 node.start._permute += step;
-                if (expr && (expr !== node.body || !has_loopcontrol(expr, node, parent))) {
+                if (expr) {
                     CHANGED = true;
                     return to_statement(expr);
                 }
@@ -389,6 +402,13 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                     CHANGED = true;
                     return List.skip;
                 }
+
+                // skip element/property from (destructured) array/object
+                if (parent instanceof U.AST_Array || parent instanceof U.AST_Destructured || parent instanceof AST_Object) {
+                    node.start._permute++;
+                    CHANGED = true;
+                    return List.skip;
+                }
             }
 
             // replace this node

test/ufuzz/index.js

@@ -377,6 +377,118 @@ function createArgs(recurmax, stmtDepth, canThrow) {
     return args.join(", ");
 }
 
+function createAssignmentPairs(recurmax, noComma, stmtDepth, canThrow, varNames, maybe, dontStore) {
+    var avoid = [];
+    var len = unique_vars.length;
+    var pairs = createPairs(recurmax);
+    unique_vars.length = len;
+    return pairs;
+
+    function createAssignmentValue(recurmax) {
+        var current = VAR_NAMES;
+        VAR_NAMES = (varNames || VAR_NAMES).slice();
+        var value = varNames && rng(2) ? createValue() : createExpression(recurmax, noComma, stmtDepth, canThrow);
+        VAR_NAMES = current;
+        return value;
+    }
+
+    function createKey(recurmax, keys) {
+        var save = VAR_NAMES;
+        VAR_NAMES = VAR_NAMES.filter(function(name) {
+            return avoid.indexOf(name) < 0;
+        });
+        var len = VAR_NAMES.length;
+        var key;
+        do {
+            key = createObjectKey(recurmax, stmtDepth, canThrow);
+        } while (keys.indexOf(key) >= 0);
+        VAR_NAMES = save.concat(VAR_NAMES.slice(len));
+        return key;
+    }
+
+    function createPairs(recurmax) {
+        var names = [], values = [];
+        var m = rng(4), n = rng(4);
+        if (!varNames) m = Math.max(m, n, 1);
+        for (var i = Math.max(m, n); --i >= 0;) {
+            if (i < m && i < n) {
+                createDestructured(recurmax, names, values);
+                continue;
+            }
+            if (i < m) {
+                unique_vars.push("a", "b", "c", "undefined", "NaN", "Infinity");
+                var name = createVarName(maybe, dontStore);
+                unique_vars.length -= 6;
+                avoid.push(name);
+                unique_vars.push(name);
+                names.unshift(name);
+            }
+            if (i < n) {
+                values.unshift(createAssignmentValue(recurmax));
+            }
+        }
+        return {
+            names: names,
+            values: values,
+        };
+    }
+
+    function createDestructured(recurmax, names, values) {
+        switch (rng(20)) {
+          case 0:
+            if (--recurmax < 0) {
+                names.unshift("[]");
+                values.unshift('""');
+            } else {
+                var pairs = createPairs(recurmax);
+                while (!rng(10)) {
+                    var index = rng(pairs.names.length + 1);
+                    pairs.names.splice(index, 0, "");
+                    pairs.values.splice(index, 0, rng(2) ? createAssignmentValue(recurmax) : "");
+                }
+                names.unshift("[ " + pairs.names.join(", ") + " ]");
+                values.unshift("[ " + pairs.values.join(", ") + " ]");
+            }
+            break;
+          case 1:
+            if (--recurmax < 0) {
+                names.unshift("{}");
+                values.unshift('""');
+            } else {
+                var pairs = createPairs(recurmax);
+                var keys = [];
+                pairs.names.forEach(function(name, index) {
+                    if (/^[[{]/.test(name)) {
+                        var key;
+                        do {
+                            key = KEYS[rng(KEYS.length)];
+                        } while (keys.indexOf(key) >= 0);
+                        keys[index] = key;
+                    }
+                });
+                names.unshift("{ " + pairs.names.map(function(name, index) {
+                    var key = index in keys ? keys[index] : rng(10) && createKey(recurmax, keys);
+                    return key ? key + ": " + name : name;
+                }).join(", ") + " }");
+                values.unshift("{ " + pairs.values.map(function(value, index) {
+                    var key = index in keys ? keys[index] : createKey(recurmax, keys);
+                    return key + ": " + value;
+                }).join(", ") + " }");
+            }
+            break;
+          default:
+            unique_vars.push("a", "b", "c", "undefined", "NaN", "Infinity");
+            var name = createVarName(maybe, dontStore);
+            unique_vars.length -= 6;
+            avoid.push(name);
+            unique_vars.push(name);
+            names.unshift(name);
+            values.unshift(createAssignmentValue(recurmax));
+            break;
+        }
+    }
+}
+
 function filterDirective(s) {
     if (!generate_directive && !s[1] && /\("/.test(s[2])) s[2] = ";" + s[2];
     return s;
@@ -415,11 +527,37 @@ function createBlockVariables(recurmax, stmtDepth, canThrow, fn) {
             return names.indexOf(name) < 0;
         });
         var len = VAR_NAMES.length;
-        var s = type + " " + names.map(function(name) {
+        var s = type + " ";
+        switch (rng(10)) {
+          case 0:
+            while (!rng(10)) names.splice(rng(names.length + 1), 0, "");
+            s += "[ " + names.join(", ") + " ] = [ " + names.map(function() {
+                return rng(10) ? createExpression(recurmax, NO_COMMA, stmtDepth, canThrow) : "";
+            }).join(", ") + " ];";
+            break;
+          case 1:
+            var keys = [];
+            s += "{ " + names.map(function(name, i) {
+                var key = createObjectKey(recurmax, stmtDepth, canThrow);
+                if (!/\[/.test(key)) keys[i] = key;
+                return key + ": " + name;
+            }).join(", ") + "} = { " + names.map(function(name, i) {
+                var key = i in keys ? keys[i] : createObjectKey(recurmax, stmtDepth, canThrow);
+                return key + ": " + createExpression(recurmax, NO_COMMA, stmtDepth, canThrow);
+            }).join(", ") + "};";
+            break;
+          default:
+            s += names.map(function(name, i) {
+                if (type == "let" && !rng(10)) {
+                    VAR_NAMES.push(name);
+                    return name;
+                }
                 var value = createExpression(recurmax, NO_COMMA, stmtDepth, canThrow);
                 VAR_NAMES.push(name);
                 return name + " = " + value;
             }).join(", ") + ";";
+            break;
+        }
         VAR_NAMES = save.concat(VAR_NAMES.slice(len));
         return s;
     }
@@ -429,9 +567,9 @@ function createFunction(recurmax, allowDefun, canThrow, stmtDepth) {
     if (--recurmax < 0) { return ";"; }
     if (!STMT_COUNT_FROM_GLOBAL) stmtDepth = 0;
     var s = [];
-    var name;
+    var name, args;
+    var varNames = VAR_NAMES.slice();
     createBlockVariables(recurmax, stmtDepth, canThrow, function(defns) {
-        var namesLenBefore = VAR_NAMES.length;
         if (allowDefun || rng(5) > 0) {
             name = "f" + funcs++;
         } else {
@@ -439,7 +577,16 @@ function createFunction(recurmax, allowDefun, canThrow, stmtDepth) {
             name = createVarName(MANDATORY, !allowDefun);
             unique_vars.length -= 3;
         }
-        s.push("function " + name + "(" + createParams() + "){", strictMode());
+        var params;
+        if ((!allowDefun || !(name in called)) && rng(2)) {
+            called[name] = false;
+            var pairs = createAssignmentPairs(recurmax, COMMA_OK, stmtDepth, canThrow, varNames, MANDATORY);
+            params = pairs.names.join(", ");
+            args = pairs.values.join(", ");
+        } else {
+            params = createParams();
+        }
+        s.push("function " + name + "(" + params + "){", strictMode());
         s.push(defns());
         if (rng(5) === 0) {
             // functions with functions. lower the recursion to prevent a mess.
@@ -450,17 +597,16 @@ function createFunction(recurmax, allowDefun, canThrow, stmtDepth) {
         }
         s.push("}", "");
         s = filterDirective(s).join("\n");
-
-        VAR_NAMES.length = namesLenBefore;
     });
+    VAR_NAMES = varNames;
 
     if (!allowDefun) {
         // avoid "function statements" (decl inside statements)
         s = "var " + createVarName(MANDATORY) + " = " + s;
-        s += "(" + createArgs(recurmax, stmtDepth, canThrow) + ")";
-    } else if (!(name in called) || rng(3) > 0) {
+        s += "(" + (args || createArgs(recurmax, stmtDepth, canThrow)) + ")";
+    } else if (!(name in called) || args || rng(3)) {
         s += "var " + createVarName(MANDATORY) + " = " + name;
-        s += "(" + createArgs(recurmax, stmtDepth, canThrow) + ")";
+        s += "(" + (args || createArgs(recurmax, stmtDepth, canThrow)) + ")";
     }
 
     return s + ";";
@@ -561,8 +707,9 @@ function createStatement(recurmax, canThrow, canBreak, canContinue, cannotReturn
         return [
             "{var expr" + loop + " = " + createExpression(recurmax, COMMA_OK, stmtDepth, canThrow) + "; ",
             label.target + " for (",
-            /^key/.test(key) ? "var " : "",
-            key + " in expr" + loop + ") {",
+            !/^key/.test(key) ? rng(10) ? "" : "var " : rng(10) ? "var " : rng(2) ? "let " : "const ",
+            rng(20) ? key : "{ length: " + key + " }",
+            " in expr" + loop + ") {",
             rng(5) > 1 ? "c = 1 + c; var " + createVarName(MANDATORY) + " = expr" + loop + "[" + key + "]; " : "",
             createStatement(recurmax, canThrow, canBreak, canContinue, cannotReturn, stmtDepth),
             "}}",
@@ -576,7 +723,12 @@ function createStatement(recurmax, canThrow, canBreak, canContinue, cannotReturn
         // note: default does not _need_ to be last
         return "switch (" + createExpression(recurmax, COMMA_OK, stmtDepth, canThrow) + ") { " + createSwitchParts(recurmax, 4, canThrow, canBreak, canContinue, cannotReturn, stmtDepth) + "}";
       case STMT_VAR:
-        switch (rng(3)) {
+        if (!rng(20)) {
+            var pairs = createAssignmentPairs(recurmax, NO_COMMA, stmtDepth, canThrow, null, MANDATORY);
+            return "var " + pairs.names.map(function(name, index) {
+                return index in pairs.values ? name + " = " + pairs.values[index] : name;
+            }).join(", ") + ";";
+        } else switch (rng(3)) {
           case 0:
             unique_vars.push("c");
             var name = createVarName(MANDATORY);
@@ -719,7 +871,28 @@ function _createExpression(recurmax, noComma, stmtDepth, canThrow) {
       case p++:
         return getVarName();
       case p++:
+        switch (rng(20)) {
+          case 0:
+            return [
+                "[ ",
+                new Array(rng(3)).join(","),
+                getVarName(NO_CONST),
+                new Array(rng(3)).join(","),
+                " ] = ",
+                createArrayLiteral(recurmax, stmtDepth, canThrow),
+            ].join("");
+          case 1:
+            return [
+                "{ ",
+                rng(2) ? "" : createObjectKey(recurmax, stmtDepth, canThrow) + ": ",
+                getVarName(NO_CONST),
+                " } = ",
+                createExpression(recurmax, COMMA_OK, stmtDepth, canThrow),
+                " || {}",
+            ].join("");
+          default:
             return getVarName(NO_CONST) + createAssignment() + createExpression(recurmax, COMMA_OK, stmtDepth, canThrow);
+        }
       case p++:
         return createExpression(recurmax, COMMA_OK, stmtDepth, canThrow);
       case p++:
@@ -864,7 +1037,10 @@ function _createExpression(recurmax, noComma, stmtDepth, canThrow) {
       case p++:
       case p++:
       case p++:
-        var name = rng(3) == 0 ? getVarName() : "f" + rng(funcs + 2);
+        var name;
+        do {
+            name = rng(3) == 0 ? getVarName() : "f" + rng(funcs + 2);
+        } while (name in called && !called[name]);
         called[name] = true;
         return "typeof " + name + ' == "function" && --_calls_ >= 0 && ' + name + "(" + createArgs(recurmax, stmtDepth, canThrow) + ")";
     }
@@ -1002,13 +1178,77 @@ function _createSimpleBinaryExpr(recurmax, noComma, stmtDepth, canThrow) {
         return "(" + assignee + createAssignment() + _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow) + ")";
       case 3:
         assignee = getVarName();
-        expr = "(" + assignee + "[" + createExpression(recurmax, COMMA_OK, stmtDepth, canThrow)
-            + "]" + createAssignment() + _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow) + ")";
+        switch (rng(20)) {
+          case 0:
+            expr = [
+                "([ ",
+                assignee,
+                "[", createExpression(recurmax, COMMA_OK, stmtDepth, canThrow), "]",
+                " ] = [ ",
+                _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow),
+                " ])",
+            ].join("");
+            break;
+          case 1:
+            var key1 = createObjectKey(recurmax, stmtDepth, canThrow);
+            var key2 = /^\[/.test(key1) ? createObjectKey(recurmax, stmtDepth, canThrow) : key1;
+            expr = [
+                "({ ",
+                key1, ": ", assignee,
+                "[", createExpression(recurmax, COMMA_OK, stmtDepth, canThrow), "]",
+                " } = { ",
+                key2, ": ", _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow),
+                " })",
+            ].join("");
+            break;
+          default:
+            expr = [
+                "(",
+                assignee,
+                "[", createExpression(recurmax, COMMA_OK, stmtDepth, canThrow), "]",
+                createAssignment(),
+                _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow),
+                ")",
+            ].join("");
+            break;
+        }
         return canThrow && rng(10) == 0 ? expr : "(" + assignee + " && " + expr + ")";
       case 4:
         assignee = getVarName();
-        expr = "(" + assignee + "." + getDotKey(true) + createAssignment()
-            + _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow) + ")";
+        switch (rng(20)) {
+          case 0:
+            expr = [
+                "([ ",
+                assignee,
+                ".", getDotKey(true),
+                " ] = [ ",
+                _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow),
+                " ])",
+            ].join("");
+            break;
+          case 1:
+            var key1 = createObjectKey(recurmax, stmtDepth, canThrow);
+            var key2 = /^\[/.test(key1) ? createObjectKey(recurmax, stmtDepth, canThrow) : key1;
+            expr = [
+                "({ ",
+                key1, ": ", assignee,
+                ".", getDotKey(true),
+                " } = { ",
+                key2, ": ", _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow),
+                " })",
+            ].join("");
+            break;
+          default:
+            expr = [
+                "(",
+                assignee,
+                ".", getDotKey(true),
+                createAssignment(),
+                _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow),
+                ")",
+            ].join("");
+            break;
+        }
         return canThrow && rng(10) == 0 ? expr : "(" + assignee + " && " + expr + ")";
       default:
         return _createBinaryExpr(recurmax, noComma, stmtDepth, canThrow);
@@ -1351,7 +1591,14 @@ function patch_try_catch(orig, toplevel) {
     }
 }
 
-var minify_options = require("./options.json").map(JSON.stringify);
+var minify_options = require("./options.json");
+if (typeof sandbox.run_code("console.log([ 1 ], {} = 2);") != "string") {
+    minify_options.forEach(function(o) {
+        if (!("output" in o)) o.output = {};
+        o.output.v8 = true;
+    });
+}
+minify_options = minify_options.map(JSON.stringify);
 var original_code, original_result, errored;
 var uglify_code, uglify_result, ok;
 for (var round = 1; round <= num_iterations; round++) {