From 555c7898c8afa7318e8e8074b84d01d950146b3c Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Thu, 22 Jan 2015 18:21:38 +0200
Subject: [PATCH 01/14] Remove Token::{startLoc,endLoc} so they don't appear in
 next release.

---
 acorn.js | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/acorn.js b/acorn.js
index 10cac96e47..f4b1534bac 100644
--- a/acorn.js
+++ b/acorn.js
@@ -200,9 +200,6 @@
     if (options.locations) {
       this.loc = new SourceLocation();
       this.loc.end = tokEndLoc;
-      // TODO: remove in next major release
-      this.startLoc = tokStartLoc;
-      this.endLoc = tokEndLoc;
     }
     if (options.ranges)
       this.range = [tokStart, tokEnd];

From 2e55540bbee9475d3249e3442a2a3e640bf16808 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Thu, 22 Jan 2015 18:53:45 +0200
Subject: [PATCH 02/14] Fix {start,end}Loc -> loc.{start,end} in acorn_loose;
 remove forceRegexp.

---
 acorn_loose.js | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/acorn_loose.js b/acorn_loose.js
index 27e8b65e63..db2883c4bf 100644
--- a/acorn_loose.js
+++ b/acorn_loose.js
@@ -58,14 +58,12 @@
   var lastEnd, token = {start: 0, end: 0}, ahead = [];
   var curLineStart, nextLineStart, curIndent, lastEndLoc, sourceFile;
 
-  function next(forceRegexp) {
+  function next() {
     lastEnd = token.end;
     if (options.locations)
-      lastEndLoc = token.endLoc;
-    if (forceRegexp)
-      ahead.length = 0;
+      lastEndLoc = token.loc && token.loc.end;
 
-    token = ahead.shift() || readToken(forceRegexp);
+    token = ahead.shift() || readToken();
     if (options.onToken)
       options.onToken(token);
 
@@ -78,10 +76,10 @@
     }
   }
 
-  function readToken(forceRegexp) {
+  function readToken() {
     for (;;) {
       try {
-        var tok = fetchToken(forceRegexp);
+        var tok = fetchToken();
         if (tok.type === tt.dot && input.substr(tok.end, 1) === '.') {
           tok = fetchToken();
           tok.start--;
@@ -129,8 +127,8 @@
         if (replace === true) replace = {start: pos, end: pos, type: tt.name, value: "✖"};
         if (replace) {
           if (options.locations) {
-            replace.startLoc = acorn.getLineInfo(input, replace.start);
-            replace.endLoc = acorn.getLineInfo(input, replace.end);
+            replace.loc = new SourceLocation(acorn.getLineInfo(input, replace.start));
+            replace.loc.end = acorn.getLineInfo(input, replace.end);
           }
           return replace;
         }
@@ -212,7 +210,7 @@
   Node.prototype = acorn.Node.prototype;
 
   function SourceLocation(start) {
-    this.start = start || token.startLoc || {line: 1, column: 0};
+    this.start = start || token.loc.start || {line: 1, column: 0};
     this.end = null;
     if (sourceFile !== null) this.source = sourceFile;
   }
@@ -229,7 +227,7 @@
   }
 
   function storeCurrentPos() {
-    return options.locations ? [token.start, token.startLoc] : token.start;
+    return options.locations ? [token.start, token.loc.start] : token.start;
   }
 
   function startNodeAt(pos) {
@@ -313,7 +311,7 @@
     node.body = [];
     while (token.type !== tt.eof) node.body.push(parseStatement());
     lastEnd = token.end;
-    lastEndLoc = token.endLoc;
+    lastEndLoc = token.loc && token.loc.end;
     return finishNode(node, "Program");
   }
 
@@ -913,7 +911,7 @@
       // If there is no closing brace, make the node span to the start
       // of the next token (this is useful for Tern)
       lastEnd = token.start;
-      if (options.locations) lastEndLoc = token.startLoc;
+      if (options.locations) lastEndLoc = token.loc.start;
     }
     if (isClass) {
       semicolon();
@@ -1168,7 +1166,7 @@
       // If there is no closing brace, make the node span to the start
       // of the next token (this is useful for Tern)
       lastEnd = token.start;
-      if (options.locations) lastEndLoc = token.startLoc;
+      if (options.locations) lastEndLoc = token.loc.start;
     }
     return elts;
   }

From 39d752dc6b446380b77c2c2143150455e13cb8c2 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 11:48:39 +0200
Subject: [PATCH 03/14] Make top-level equal to block statement context.

Fixes #203.
---
 acorn.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/acorn.js b/acorn.js
index f4b1534bac..c60c6eac45 100644
--- a/acorn.js
+++ b/acorn.js
@@ -614,7 +614,7 @@
       tokPos = tokLineStart = 0;
     }
     tokType = _eof;
-    tokContext = [];
+    tokContext = [b_stat];
     tokExprAllowed = true;
     if (tokPos === 0 && options.allowHashBang && input.slice(0, 2) === '#!') {
       skipLineComment(2);

From e6f1e1027e9a9075b5572a9c495630b8a1d7870a Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 13:17:03 +0200
Subject: [PATCH 04/14] Fix dividing function expression.

Fixes #204.
---
 acorn.js      | 29 +++++++++++++++++++++--------
 test/tests.js | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 8 deletions(-)

diff --git a/acorn.js b/acorn.js
index c60c6eac45..334b3ff1d8 100644
--- a/acorn.js
+++ b/acorn.js
@@ -627,18 +627,22 @@
 
   var b_stat = {token: "{", isExpr: false}, b_expr = {token: "{", isExpr: true}, b_tmpl = {token: "${", isExpr: true};
   var p_stat = {token: "(", isExpr: false}, p_expr = {token: "(", isExpr: true};
-  var q_tmpl = {token: "`", isExpr: true};
+  var q_tmpl = {token: "`", isExpr: true}, f_expr = {token: "function", isExpr: true};
+
+  function curTokContext() {
+    return tokContext[tokContext.length - 1];
+  }
 
   function braceIsBlock(prevType) {
     var parent;
-    if (prevType === _colon && (parent = tokContext[tokContext.length - 1]).token == "{")
+    if (prevType === _colon && (parent = curTokContext()).token == "{")
       return !parent.isExpr;
     if (prevType === _return)
       return newline.test(input.slice(lastEnd, tokStart));
     if (prevType === _else || prevType === _semi || prevType === _eof)
       return true;
     if (prevType == _braceL)
-      return tokContext[tokContext.length - 1] === b_stat;
+      return curTokContext() === b_stat;
     return !tokExprAllowed;
   }
 
@@ -657,8 +661,14 @@
     // Update context info
     if (type === _parenR || type === _braceR) {
       var out = tokContext.pop();
-      tokExprAllowed = !(out && out.isExpr);
-      preserveSpace = out === b_tmpl;
+      if (out === b_tmpl) {
+        preserveSpace = true;
+      } else if (out === b_stat && curTokContext() === f_expr) {
+        tokContext.pop();
+        tokExprAllowed = false;
+      } else {
+        tokExprAllowed = !(out && out.isExpr);
+      }
     } else if (type === _braceL) {
       tokContext.push(braceIsBlock(prevType) ? b_stat : b_expr);
       tokExprAllowed = true;
@@ -673,10 +683,13 @@
       // tokExprAllowed stays unchanged
     } else if (type.keyword && prevType == _dot) {
       tokExprAllowed = false;
-    } else if (tokExprAllowed && type == _function) {
+    } else if (type == _function) {
+      if (curTokContext() !== b_stat) {
+        tokContext.push(f_expr);
+      }
       tokExprAllowed = false;
     } else if (type === _backQuote) {
-      if (tokContext[tokContext.length - 1] === q_tmpl) {
+      if (curTokContext() === q_tmpl) {
         tokContext.pop();
       } else {
         tokContext.push(q_tmpl);
@@ -939,7 +952,7 @@
     if (options.locations) tokStartLoc = curPosition();
     if (tokPos >= inputLen) return finishToken(_eof);
 
-    if (tokContext[tokContext.length - 1] === q_tmpl) {
+    if (curTokContext() === q_tmpl) {
       return readTmplToken();
     }
 
diff --git a/test/tests.js b/test/tests.js
index 172eb1fb87..dee69bb4a3 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -28862,3 +28862,48 @@ test("#!/usr/bin/node\n;", {}, {
     end: 15
   }]
 });
+
+// https://github.com/marijnh/acorn/issues/204
+test("(function () {} / 1)", {
+  type: "Program",
+  body: [{
+    type: "ExpressionStatement",
+    expression: {
+      type: "BinaryExpression",
+      left: {
+        type: "FunctionExpression",
+        id: null,
+        params: [],
+        body: {
+          type: "BlockStatement",
+          body: []
+        }
+      },
+      operator: "/",
+      right: {type: "Literal", value: 1}
+    }
+  }]
+});
+
+test("function f() {} / 1 /", {
+  type: "Program",
+  body: [
+    {
+      type: "FunctionDeclaration",
+      id: {type: "Identifier", name: "f"},
+      params: [],
+      body: {
+        type: "BlockStatement",
+        body: []
+      }
+    },
+    {
+      type: "ExpressionStatement",
+      expression: {
+        type: "Literal",
+        regex: {pattern: " 1 ", flags: ""},
+        value: {}
+      }
+    }
+  ]
+});

From cb94a0851c5574d9f5380e805cca698c0b0bec83 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 13:50:01 +0200
Subject: [PATCH 05/14] Add regex comparison to test driver.

---
 test/driver.js        |  5 ++++-
 test/tests-harmony.js | 38 +++++++++++++++++++-------------------
 test/tests.js         | 18 +++++++++---------
 3 files changed, 32 insertions(+), 29 deletions(-)

diff --git a/test/driver.js b/test/driver.js
index c76b8f91a4..7b7dee853c 100644
--- a/test/driver.js
+++ b/test/driver.js
@@ -66,7 +66,7 @@
     }
   };
 
-  function ppJSON(v) { return JSON.stringify(v, null, 2); }
+  function ppJSON(v) { return v instanceof RegExp ? v.toString() : JSON.stringify(v, null, 2); }
   function addPath(str, pt) {
     if (str.charAt(str.length-1) == ")")
       return str.slice(0, str.length-1) + "/" + pt + ")";
@@ -76,6 +76,9 @@
   var misMatch = exports.misMatch = function(exp, act) {
     if (!exp || !act || (typeof exp != "object") || (typeof act != "object")) {
       if (exp !== act) return ppJSON(exp) + " !== " + ppJSON(act);
+    } else if (exp instanceof RegExp || act instanceof RegExp) {
+      var left = ppJSON(exp), right = ppJSON(act);
+      if (left !== right) return left + " !== " + right;
     } else if (exp.splice) {
       if (!act.slice) return ppJSON(exp) + " != " + ppJSON(act);
       if (act.length != exp.length) return "array length mismatch " + exp.length + " != " + act.length;
diff --git a/test/tests-harmony.js b/test/tests-harmony.js
index 07bf912d01..c0c74b8113 100644
--- a/test/tests-harmony.js
+++ b/test/tests-harmony.js
@@ -14783,47 +14783,47 @@ test("class A { *static() {} }", {
   locations: true
 });
 
-test("`${/\d/.exec('1')[0]}`", {
+test("`${/\\d/.exec('1')[0]}`", {
   "type": "Program",
   "start": 0,
-  "end": 21,
+  "end": 22,
   "body": [
     {
       "type": "ExpressionStatement",
       "start": 0,
-      "end": 21,
+      "end": 22,
       "expression": {
         "type": "TemplateLiteral",
         "start": 0,
-        "end": 21,
+        "end": 22,
         "expressions": [
           {
             "type": "MemberExpression",
             "start": 3,
-            "end": 19,
+            "end": 20,
             "object": {
               "type": "CallExpression",
               "start": 3,
-              "end": 16,
+              "end": 17,
               "callee": {
                 "type": "MemberExpression",
                 "start": 3,
-                "end": 11,
+                "end": 12,
                 "object": {
                   "type": "Literal",
                   "start": 3,
-                  "end": 6,
+                  "end": 7,
                   "regex": {
-                    "pattern": "d",
+                    "pattern": "\\d",
                     "flags": ""
                   },
-                  "value": {},
-                  "raw": "/d/"
+                  "value": /\d/,
+                  "raw": "/\\d/"
                 },
                 "property": {
                   "type": "Identifier",
-                  "start": 7,
-                  "end": 11,
+                  "start": 8,
+                  "end": 12,
                   "name": "exec"
                 },
                 "computed": false
@@ -14831,8 +14831,8 @@ test("`${/\d/.exec('1')[0]}`", {
               "arguments": [
                 {
                   "type": "Literal",
-                  "start": 12,
-                  "end": 15,
+                  "start": 13,
+                  "end": 16,
                   "value": "1",
                   "raw": "'1'"
                 }
@@ -14840,8 +14840,8 @@ test("`${/\d/.exec('1')[0]}`", {
             },
             "property": {
               "type": "Literal",
-              "start": 17,
-              "end": 18,
+              "start": 18,
+              "end": 19,
               "value": 0,
               "raw": "0"
             },
@@ -14861,8 +14861,8 @@ test("`${/\d/.exec('1')[0]}`", {
           },
           {
             "type": "TemplateElement",
-            "start": 20,
-            "end": 20,
+            "start": 21,
+            "end": 21,
             "value": {
               "raw": "",
               "cooked": ""
diff --git a/test/tests.js b/test/tests.js
index dee69bb4a3..d3beafc5f9 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -169,7 +169,7 @@ test("/[a-z]/g", {
       type: "ExpressionStatement",
       expression: {
         type: "Literal",
-        value: /[a-z]/,
+        value: /[a-z]/g,
         regex: {
           pattern: "[a-z]",
           flags: "g"
@@ -7331,7 +7331,7 @@ test("var x = /[a-z]/i", {
           },
           init: {
             type: "Literal",
-            value: {},
+            value: /[a-z]/i,
             loc: {
               start: {
                 line: 1,
@@ -7404,7 +7404,7 @@ test("var x = /[x-z]/i", {
           },
           init: {
             type: "Literal",
-            value: {},
+            value: /[x-z]/i,
             loc: {
               start: {
                 line: 1,
@@ -7477,7 +7477,7 @@ test("var x = /[a-c]/i", {
           },
           init: {
             type: "Literal",
-            value: {},
+            value: /[a-c]/i,
             loc: {
               start: {
                 line: 1,
@@ -7550,7 +7550,7 @@ test("var x = /[P QR]/i", {
           },
           init: {
             type: "Literal",
-            value: {},
+            value: /[P QR]/i,
             loc: {
               start: {
                 line: 1,
@@ -7623,7 +7623,7 @@ test("var x = /foo\\/bar/", {
           },
           init: {
             type: "Literal",
-            value: {},
+            value: /foo\/bar/,
             loc: {
               start: {
                 line: 1,
@@ -7696,7 +7696,7 @@ test("var x = /=([^=\\s])+/g", {
           },
           init: {
             type: "Literal",
-            value: {},
+            value: /=([^=\s])+/g,
             loc: {
               start: {
                 line: 1,
@@ -7769,7 +7769,7 @@ test("var x = /[P QR]/\\u0067", {
           },
           init: {
             type: "Literal",
-            value: {},
+            value: /[P QR]/g,
             loc: {
               start: {
                 line: 1,
@@ -28902,7 +28902,7 @@ test("function f() {} / 1 /", {
       expression: {
         type: "Literal",
         regex: {pattern: " 1 ", flags: ""},
-        value: {}
+        value: / 1 /
       }
     }
   ]

From 38609ae26d6fa071194026d4e15e9bd7d21fea82 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 14:14:02 +0200
Subject: [PATCH 06/14] Closes #205.

---
 acorn.js              | 32 ++++++++++++++++++--------------
 acorn_loose.js        |  5 +++--
 test/tests-harmony.js | 18 +++++++++---------
 3 files changed, 30 insertions(+), 25 deletions(-)

diff --git a/acorn.js b/acorn.js
index 334b3ff1d8..491a3e2f23 100644
--- a/acorn.js
+++ b/acorn.js
@@ -1458,6 +1458,7 @@
         case "ObjectPattern":
         case "ArrayPattern":
         case "AssignmentPattern":
+        case "RestElement":
           break;
 
         case "ObjectExpression":
@@ -1478,6 +1479,7 @@
 
         case "SpreadElement":
           if (allowSpread) {
+            node.type = "RestElement";
             toAssignable(node.argument, false, checkType);
             checkSpreadAssign(node.argument);
           } else {
@@ -1502,17 +1504,19 @@
 
   // Parses spread element.
 
-  function parseSpread(isBinding) {
-    var spread = startNode();
+  function parseSpread() {
+    var node = startNode();
     next();
-    if (isBinding) {
-      var arg = parseAssignableAtom();
-      checkSpreadAssign(arg);
-      spread.argument = arg;
-    } else {
-      spread.argument = parseMaybeAssign();
-    }
-    return finishNode(spread, "SpreadElement");
+    node.argument = parseMaybeAssign();
+    return finishNode(node, "SpreadElement");
+  }
+
+  function parseRest() {
+    var node = startNode();
+    next();
+    node.argument = parseAssignableAtom();
+    checkSpreadAssign(node.argument);
+    return finishNode(node, "RestElement");
   }
 
   // Parses lvalue (assignable) atom.
@@ -1530,7 +1534,7 @@
         while (!eat(_bracketR)) {
           first ? first = false : expect(_comma);
           if (tokType === _ellipsis) {
-            elts.push(parseSpread(true));
+            elts.push(parseRest());
             expect(_bracketR);
             break;
           }
@@ -1648,7 +1652,7 @@
         break;
 
       case "AssignmentPattern":
-      case "SpreadElement":
+      case "RestElement":
         break;
 
       default:
@@ -2270,7 +2274,7 @@
         first ? first = false : expect(_comma);
         if (tokType === _ellipsis) {
           spreadStart = tokStart;
-          exprList.push(parseSpread(true));
+          exprList.push(parseRest());
           break;
         } else {
           if (tokType === _parenL && !innerParenStart) {
@@ -2479,7 +2483,7 @@
       } else {
         toAssignable(param, i === lastI, true);
         defaults.push(null);
-        if (param.type === "SpreadElement") {
+        if (param.type === "RestElement") {
           params.length--;
           node.rest = param.argument;
           break;
diff --git a/acorn_loose.js b/acorn_loose.js
index db2883c4bf..dca43afc7b 100644
--- a/acorn_loose.js
+++ b/acorn_loose.js
@@ -297,7 +297,7 @@
       case "MemberExpression":
       case "ObjectPattern":
       case "ArrayPattern":
-      case "SpreadElement":
+      case "RestElement":
       case "AssignmentPattern":
         return expr;
 
@@ -982,6 +982,7 @@
           break;
 
         case "SpreadElement":
+          node.type = "RestElement";
           node.argument = toAssignable(node.argument);
           break;
 
@@ -1007,7 +1008,7 @@
         param = param.left;
       }
       param = toAssignable(param);
-      if (param.type === "SpreadElement") {
+      if (param.type === "RestElement") {
         param = param.argument;
         if (i === params.length - 1) {
           node.rest = param;
diff --git a/test/tests-harmony.js b/test/tests-harmony.js
index c0c74b8113..82eafb146d 100644
--- a/test/tests-harmony.js
+++ b/test/tests-harmony.js
@@ -12913,7 +12913,7 @@ test("[...a] = b", {
       left: {
         type: "ArrayPattern",
         elements: [{
-          type: "SpreadElement",
+          type: "RestElement",
           argument: {
             type: "Identifier",
             name: "a",
@@ -12979,7 +12979,7 @@ test("[a, ...b] = c", {
             }
           },
           {
-            type: "SpreadElement",
+            type: "RestElement",
             argument: {
               type: "Identifier",
               name: "b",
@@ -13101,7 +13101,7 @@ test("[{ a, b }, ...c] = d", {
             }
           },
           {
-            type: "SpreadElement",
+            type: "RestElement",
             argument: {
               type: "Identifier",
               name: "c",
@@ -13168,7 +13168,7 @@ test("[a, ...[b, c]] = d", {
             }
           },
           {
-            type: "SpreadElement",
+            type: "RestElement",
             argument: {
               type: "ArrayPattern",
               elements: [
@@ -13242,7 +13242,7 @@ test("var [...a] = b", {
       id: {
         type: "ArrayPattern",
         elements: [{
-          type: "SpreadElement",
+          type: "RestElement",
           argument: {
             type: "Identifier",
             name: "a",
@@ -13308,7 +13308,7 @@ test("var [a, ...b] = c", {
             }
           },
           {
-            type: "SpreadElement",
+            type: "RestElement",
             argument: {
               type: "Identifier",
               name: "b",
@@ -13430,7 +13430,7 @@ test("var [{ a, b }, ...c] = d", {
             }
           },
           {
-            type: "SpreadElement",
+            type: "RestElement",
             argument: {
               type: "Identifier",
               name: "c",
@@ -13497,7 +13497,7 @@ test("var [a, ...[b, c]] = d", {
             }
           },
           {
-            type: "SpreadElement",
+            type: "RestElement",
             argument: {
               type: "ArrayPattern",
               elements: [
@@ -14195,7 +14195,7 @@ test("[...a, ] = b", {
           end: {line: 1, column: 8}
         },
         elements: [{
-          type: "SpreadElement",
+          type: "RestElement",
           loc: {
             start: {line: 1, column: 1},
             end: {line: 1, column: 5}

From 917de714b145882aa65d21c121eeeae0e76b4c99 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 15:29:37 +0200
Subject: [PATCH 07/14] Switch from Function.{rest,defaults} to
 AssignmentPattern and RestElement.

Closes #182.
---
 acorn.js              |  113 +-
 acorn_loose.js        |   49 +-
 test/tests-harmony.js | 2433 ++++++++++++++++++++---------------------
 test/tests.js         |   87 +-
 4 files changed, 1251 insertions(+), 1431 deletions(-)

diff --git a/acorn.js b/acorn.js
index 491a3e2f23..6cf6a60443 100644
--- a/acorn.js
+++ b/acorn.js
@@ -1472,9 +1472,7 @@
 
         case "ArrayExpression":
           node.type = "ArrayPattern";
-          for (var i = 0, lastI = node.elements.length - 1; i <= lastI; i++) {
-            toAssignable(node.elements[i], i === lastI, checkType);
-          }
+          toAssignableList(node.elements, checkType);
           break;
 
         case "SpreadElement":
@@ -1502,6 +1500,15 @@
     return node;
   }
 
+  // Convert list of expression atoms to binding list.
+
+  function toAssignableList(exprList, checkType) {
+    for (var i = 0; i < exprList.length; i++) {
+      toAssignable(exprList[i], i === exprList.length - 1, checkType);
+    }
+    return exprList;
+  }
+
   // Parses spread element.
 
   function parseSpread() {
@@ -1530,16 +1537,7 @@
       case _bracketL:
         var node = startNode();
         next();
-        var elts = node.elements = [], first = true;
-        while (!eat(_bracketR)) {
-          first ? first = false : expect(_comma);
-          if (tokType === _ellipsis) {
-            elts.push(parseRest());
-            expect(_bracketR);
-            break;
-          }
-          elts.push(tokType === _comma ? null : parseMaybeDefault());
-        }
+        node.elements = parseAssignableList(_bracketR, true);
         return finishNode(node, "ArrayPattern");
 
       case _braceL:
@@ -1550,6 +1548,20 @@
     }
   }
 
+  function parseAssignableList(close, allowEmpty) {
+    var elts = [], first = true;
+    while (!eat(close)) {
+      first ? first = false : expect(_comma);
+      if (tokType === _ellipsis) {
+        elts.push(parseRest());
+        expect(close);
+        break;
+      }
+      elts.push(allowEmpty && tokType === _comma ? null : parseMaybeDefault());
+    }
+    return elts;
+  }
+
   // Parses assignment pattern around given atom if possible.
 
   function parseMaybeDefault(startPos, left) {
@@ -1593,6 +1605,9 @@
           if (elem) checkFunctionParam(elem, nameHash);
         }
         break;
+
+      case "RestElement":
+        return checkFunctionParam(param.argument, nameHash);
     }
   }
 
@@ -2425,11 +2440,9 @@
 
   function initFunction(node) {
     node.id = null;
-    node.params = [];
     if (options.ecmaVersion >= 6) {
-      node.defaults = [];
-      node.rest = null;
       node.generator = false;
+      node.expression = false;
     }
   }
 
@@ -2444,7 +2457,8 @@
     if (isStatement || tokType === _name) {
       node.id = parseIdent();
     }
-    parseFunctionParams(node);
+    expect(_parenL);
+    node.params = parseAssignableList(_parenR, false);
     parseFunctionBody(node, allowExpressionBody);
     return finishNode(node, isStatement ? "FunctionDeclaration" : "FunctionExpression");
   }
@@ -2454,7 +2468,8 @@
   function parseMethod(isGenerator) {
     var node = startNode();
     initFunction(node);
-    parseFunctionParams(node);
+    expect(_parenL);
+    node.params = parseAssignableList(_parenR, false);
     var allowExpressionBody;
     if (options.ecmaVersion >= 6) {
       node.generator = isGenerator;
@@ -2470,69 +2485,11 @@
 
   function parseArrowExpression(node, params) {
     initFunction(node);
-
-    var defaults = node.defaults, hasDefaults = false;
-
-    for (var i = 0, lastI = params.length - 1; i <= lastI; i++) {
-      var param = params[i];
-
-      if (param.type === "AssignmentExpression" && param.operator === "=") {
-        hasDefaults = true;
-        params[i] = param.left;
-        defaults.push(param.right);
-      } else {
-        toAssignable(param, i === lastI, true);
-        defaults.push(null);
-        if (param.type === "RestElement") {
-          params.length--;
-          node.rest = param.argument;
-          break;
-        }
-      }
-    }
-
-    node.params = params;
-    if (!hasDefaults) node.defaults = [];
-
+    node.params = toAssignableList(params, true);
     parseFunctionBody(node, true);
     return finishNode(node, "ArrowFunctionExpression");
   }
 
-  // Parse function parameters.
-
-  function parseFunctionParams(node) {
-    var defaults = [], hasDefaults = false;
-
-    expect(_parenL);
-    for (;;) {
-      if (eat(_parenR)) {
-        break;
-      } else if (eat(_ellipsis)) {
-        node.rest = parseAssignableAtom();
-        checkSpreadAssign(node.rest);
-        expect(_parenR);
-        defaults.push(null);
-        break;
-      } else {
-        node.params.push(parseAssignableAtom());
-        if (options.ecmaVersion >= 6) {
-          if (eat(_eq)) {
-            hasDefaults = true;
-            defaults.push(parseExpression(true));
-          } else {
-            defaults.push(null);
-          }
-        }
-        if (!eat(_comma)) {
-          expect(_parenR);
-          break;
-        }
-      }
-    }
-
-    if (hasDefaults) node.defaults = defaults;
-  }
-
   // Parse function body and check parameters.
 
   function parseFunctionBody(node, allowExpression) {
@@ -2560,8 +2517,6 @@
         checkFunctionParam(node.id, {});
       for (var i = 0; i < node.params.length; i++)
         checkFunctionParam(node.params[i], nameHash);
-      if (node.rest)
-        checkFunctionParam(node.rest, nameHash);
     }
   }
 
diff --git a/acorn_loose.js b/acorn_loose.js
index dca43afc7b..e1ee14fc3c 100644
--- a/acorn_loose.js
+++ b/acorn_loose.js
@@ -952,8 +952,6 @@
     node.id = null;
     node.params = [];
     if (options.ecmaVersion >= 6) {
-      node.defaults = [];
-      node.rest = null;
       node.generator = false;
       node.expression = false;
     }
@@ -969,16 +967,13 @@
           node.type = "ObjectPattern";
           var props = node.properties;
           for (var i = 0; i < props.length; i++) {
-            props[i].value = toAssignable(props[i].value);
+            toAssignable(props[i].value);
           }
           break;
 
         case "ArrayExpression":
           node.type = "ArrayPattern";
-          var elms = node.elements;
-          for (var i = 0; i < elms.length; i++) {
-            elms[i] = toAssignable(elms[i]);
-          }
+          toAssignableList(node.elements);
           break;
 
         case "SpreadElement":
@@ -994,33 +989,17 @@
     return checkLVal(node);
   }
 
-  function parseFunctionParams(node, params) {
-    var defaults = [], hasDefaults = false;
-
-    if (!params) {
-      pushCx();
-      params = parseExprList(tt.parenR);
-    }
-    for (var i = 0; i < params.length; i++) {
-      var param = params[i], defValue = null;
-      if (param.type === "AssignmentExpression") {
-        defValue = param.right;
-        param = param.left;
-      }
-      param = toAssignable(param);
-      if (param.type === "RestElement") {
-        param = param.argument;
-        if (i === params.length - 1) {
-          node.rest = param;
-          continue;
-        }
-      }
-      node.params.push(param);
-      defaults.push(defValue);
-      if (defValue) hasDefaults = true;
+  function toAssignableList(exprList) {
+    for (var i = 0; i < exprList.length; i++) {
+      toAssignable(exprList[i]);
     }
+    return exprList;
+  }
 
-    if (hasDefaults) node.defaults = defaults;
+  function parseFunctionParams(params) {
+    pushCx();
+    params = parseExprList(tt.parenR);
+    return toAssignableList(params);
   }
 
   function parseFunction(node, isStatement) {
@@ -1030,7 +1009,7 @@
     }
     if (token.type === tt.name) node.id = parseIdent();
     else if (isStatement) node.id = dummyIdent();
-    parseFunctionParams(node);
+    node.params = parseFunctionParams();
     node.body = parseBlock();
     return finishNode(node, isStatement ? "FunctionDeclaration" : "FunctionExpression");
   }
@@ -1038,7 +1017,7 @@
   function parseMethod(isGenerator) {
     var node = startNode();
     initFunction(node);
-    parseFunctionParams(node);
+    node.params = parseFunctionParams();
     node.generator = isGenerator || false;
     node.expression = options.ecmaVersion >= 6 && token.type !== tt.braceL;
     node.body = node.expression ? parseExpression(true) : parseBlock();
@@ -1047,7 +1026,7 @@
 
   function parseArrowExpression(node, params) {
     initFunction(node);
-    parseFunctionParams(node, params);
+    node.params = toAssignableList(params);
     node.expression = token.type !== tt.braceL;
     node.body = node.expression ? parseExpression(true) : parseBlock();
     return finishNode(node, "ArrowFunctionExpression");
diff --git a/test/tests-harmony.js b/test/tests-harmony.js
index 82eafb146d..9fc9dec59c 100644
--- a/test/tests-harmony.js
+++ b/test/tests-harmony.js
@@ -174,7 +174,6 @@ test("function test() {'use strict'; 0o0; }", {
       }
     },
     params: [],
-    defaults: [],
     body: {
       type: "BlockStatement",
       body: [
@@ -216,7 +215,6 @@ test("function test() {'use strict'; 0o0; }", {
         end: {line: 1, column: 37}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -331,7 +329,6 @@ test("function test() {'use strict'; 0O0; }", {
       }
     },
     params: [],
-    defaults: [],
     body: {
       type: "BlockStatement",
       body: [
@@ -373,7 +370,6 @@ test("function test() {'use strict'; 0O0; }", {
         end: {line: 1, column: 37}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -1028,8 +1024,6 @@ test("`outer${{x: {y: 10}}}bar${`nested${function(){return 1;}}endnest`}end`",{
                 type: "FunctionExpression",
                 id: null,
                 params: [],
-                defaults: [],
-                rest: null,
                 generator: false,
                 body: {
                   type: "BlockStatement",
@@ -1198,7 +1192,6 @@ test("() => \"test\"", {
       type: "ArrowFunctionExpression",
       id: null,
       params: [],
-      defaults: [],
       body: {
         type: "Literal",
         value: "test",
@@ -1208,7 +1201,6 @@ test("() => \"test\"", {
           end: {line: 1, column: 12}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1246,7 +1238,6 @@ test("e => \"test\"", {
           end: {line: 1, column: 1}
         }
       }],
-      defaults: [],
       body: {
         type: "Literal",
         value: "test",
@@ -1256,7 +1247,6 @@ test("e => \"test\"", {
           end: {line: 1, column: 11}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1294,7 +1284,6 @@ test("(e) => \"test\"", {
           end: {line: 1, column: 2}
         }
       }],
-      defaults: [],
       body: {
         type: "Literal",
         value: "test",
@@ -1304,7 +1293,6 @@ test("(e) => \"test\"", {
           end: {line: 1, column: 13}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1352,7 +1340,6 @@ test("(a, b) => \"test\"", {
           }
         }
       ],
-      defaults: [],
       body: {
         type: "Literal",
         value: "test",
@@ -1362,7 +1349,6 @@ test("(a, b) => \"test\"", {
           end: {line: 1, column: 16}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1400,7 +1386,6 @@ test("e => { 42; }", {
           end: {line: 1, column: 1}
         }
       }],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [{
@@ -1424,7 +1409,6 @@ test("e => { 42; }", {
           end: {line: 1, column: 12}
         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -1462,7 +1446,6 @@ test("e => ({ property: 42 })", {
           end: {line: 1, column: 1}
         }
       }],
-      defaults: [],
       body: {
         type: "ObjectExpression",
         properties: [{
@@ -1498,7 +1481,6 @@ test("e => ({ property: 42 })", {
           end: {line: 1, column: 22}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1536,7 +1518,6 @@ test("e => { label: 42 }", {
           end: {line: 1, column: 1}
         }
       }],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [{
@@ -1575,7 +1556,6 @@ test("e => { label: 42 }", {
           end: {line: 1, column: 18}
         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -1623,7 +1603,6 @@ test("(a, b) => { 42; }", {
           }
         }
       ],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [{
@@ -1647,7 +1626,6 @@ test("(a, b) => { 42; }", {
           end: {line: 1, column: 17}
         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -1703,7 +1681,6 @@ test("([a, , b]) => 42", {
           end: {line: 1, column: 9}
         }
       }],
-      defaults: [],
       body: {
         type: "Literal",
         value: 42,
@@ -1713,7 +1690,6 @@ test("([a, , b]) => 42", {
           end: {line: 1, column: 16}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1774,7 +1750,6 @@ test("([a.a]) => 42", {
           end: {line: 1, column: 6}
         }
       }],
-      defaults: [],
       body: {
         type: "Literal",
         value: 42,
@@ -1784,7 +1759,6 @@ test("([a.a]) => 42", {
           end: {line: 1, column: 13}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1815,20 +1789,23 @@ test("(x=1) => x * x", {
       type: "ArrowFunctionExpression",
       id: null,
       params: [{
-        type: "Identifier",
-        name: "x",
-        loc: {
-          start: {line: 1, column: 1},
-          end: {line: 1, column: 2}
-        }
-      }],
-      defaults: [{
-        type: "Literal",
-        value: 1,
-        raw: "1",
-        loc: {
-          start: {line: 1, column: 3},
-          end: {line: 1, column: 4}
+        type: "AssignmentPattern",
+        left: {
+          type: "Identifier",
+          name: "x",
+          loc: {
+            start: {line: 1, column: 1},
+            end: {line: 1, column: 2}
+          }
+        },
+        right: {
+          type: "Literal",
+          value: 1,
+          raw: "1",
+          loc: {
+            start: {line: 1, column: 3},
+            end: {line: 1, column: 4}
+          }
         }
       }],
       body: {
@@ -1855,7 +1832,6 @@ test("(x=1) => x * x", {
           end: {line: 1, column: 14}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1893,7 +1869,6 @@ test("eval => 42", {
           end: {line: 1, column: 4}
         }
       }],
-      defaults: [],
       body: {
         type: "Literal",
         value: 42,
@@ -1903,7 +1878,6 @@ test("eval => 42", {
           end: {line: 1, column: 10}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1941,7 +1915,6 @@ test("arguments => 42", {
           end: {line: 1, column: 9}
         }
       }],
-      defaults: [],
       body: {
         type: "Literal",
         value: 42,
@@ -1951,7 +1924,6 @@ test("arguments => 42", {
           end: {line: 1, column: 15}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -1989,7 +1961,6 @@ test("(a) => 00", {
           end: {line: 1, column: 2}
         }
       }],
-      defaults: [],
       body: {
         type: "Literal",
         value: 0,
@@ -1999,7 +1970,6 @@ test("(a) => 00", {
           end: {line: 1, column: 9}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -2047,7 +2017,6 @@ test("(eval, a) => 42", {
           }
         }
       ],
-      defaults: [],
       body: {
         type: "Literal",
         value: 42,
@@ -2057,7 +2026,6 @@ test("(eval, a) => 42", {
           end: {line: 1, column: 15}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -2088,20 +2056,23 @@ test("(eval = 10) => 42", {
       type: "ArrowFunctionExpression",
       id: null,
       params: [{
-        type: "Identifier",
-        name: "eval",
-        loc: {
-          start: {line: 1, column: 1},
-          end: {line: 1, column: 5}
-        }
-      }],
-      defaults: [{
-        type: "Literal",
-        value: 10,
-        raw: "10",
-        loc: {
-          start: {line: 1, column: 8},
-          end: {line: 1, column: 10}
+        type: "AssignmentPattern",
+        left: {
+          type: "Identifier",
+          name: "eval",
+          loc: {
+            start: {line: 1, column: 1},
+            end: {line: 1, column: 5}
+          }
+        },
+        right: {
+          type: "Literal",
+          value: 10,
+          raw: "10",
+          loc: {
+            start: {line: 1, column: 8},
+            end: {line: 1, column: 10}
+          }
         }
       }],
       body: {
@@ -2113,7 +2084,6 @@ test("(eval = 10) => 42", {
           end: {line: 1, column: 17}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -2153,23 +2123,23 @@ test("(eval, a = 10) => 42", {
           }
         },
         {
-          type: "Identifier",
-          name: "a",
-          loc: {
-            start: {line: 1, column: 7},
-            end: {line: 1, column: 8}
-          }
-        }
-      ],
-      defaults: [
-        null,
-        {
-          type: "Literal",
-          value: 10,
-          raw: "10",
-          loc: {
-            start: {line: 1, column: 11},
-            end: {line: 1, column: 13}
+          type: "AssignmentPattern",
+          left: {
+            type: "Identifier",
+            name: "a",
+            loc: {
+              start: {line: 1, column: 7},
+              end: {line: 1, column: 8}
+            }
+          },
+          right: {
+            type: "Literal",
+            value: 10,
+            raw: "10",
+            loc: {
+              start: {line: 1, column: 11},
+              end: {line: 1, column: 13}
+            }
           }
         }
       ],
@@ -2182,7 +2152,6 @@ test("(eval, a = 10) => 42", {
           end: {line: 1, column: 20}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -2220,7 +2189,6 @@ test("(x => x)", {
           end: {line: 1, column: 2}
         }
       }],
-      defaults: [],
       body: {
         type: "Identifier",
         name: "x",
@@ -2229,7 +2197,6 @@ test("(x => x)", {
           end: {line: 1, column: 7}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -2267,7 +2234,6 @@ test("x => y => 42", {
           end: {line: 1, column: 1}
         }
       }],
-      defaults: [],
       body: {
         type: "ArrowFunctionExpression",
         id: null,
@@ -2279,7 +2245,6 @@ test("x => y => 42", {
             end: {line: 1, column: 6}
           }
         }],
-        defaults: [],
         body: {
           type: "Literal",
           value: 42,
@@ -2289,7 +2254,6 @@ test("x => y => 42", {
             end: {line: 1, column: 12}
           }
         },
-        rest: null,
         generator: false,
         expression: true,
         loc: {
@@ -2297,7 +2261,6 @@ test("x => y => 42", {
           end: {line: 1, column: 12}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -2335,7 +2298,6 @@ test("(x) => ((y, z) => (x, y, z))", {
           end: {line: 1, column: 2}
         }
       }],
-      defaults: [],
       body: {
         type: "ArrowFunctionExpression",
         id: null,
@@ -2357,7 +2319,6 @@ test("(x) => ((y, z) => (x, y, z))", {
             }
           }
         ],
-        defaults: [],
         body: {
           type: "SequenceExpression",
           expressions: [
@@ -2391,7 +2352,6 @@ test("(x) => ((y, z) => (x, y, z))", {
             end: {line: 1, column: 26}
           }
         },
-        rest: null,
         generator: false,
         expression: true,
         loc: {
@@ -2399,7 +2359,6 @@ test("(x) => ((y, z) => (x, y, z))", {
           end: {line: 1, column: 27}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -2440,7 +2399,6 @@ test("foo(() => {})", {
         type: "ArrowFunctionExpression",
         id: null,
         params: [],
-        defaults: [],
         body: {
           type: "BlockStatement",
           body: [],
@@ -2449,7 +2407,6 @@ test("foo(() => {})", {
             end: {line: 1, column: 12}
           }
         },
-        rest: null,
         generator: false,
         expression: false,
         loc: {
@@ -2512,7 +2469,6 @@ test("foo((x, y) => {})", {
             }
           }
         ],
-        defaults: [],
         body: {
           type: "BlockStatement",
           body: [],
@@ -2521,7 +2477,6 @@ test("foo((x, y) => {})", {
             end: {line: 1, column: 16}
           }
         },
-        rest: null,
         generator: false,
         expression: false,
         loc: {
@@ -2586,8 +2541,6 @@ test("(a, a) => 42", {
           name: "a"
         }
       ],
-      defaults: [],
-      rest: null,
       generator: false,
       body: {
         type: "Literal",
@@ -2640,7 +2593,6 @@ test("x = { method() { } }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -2649,7 +2601,6 @@ test("x = { method() { } }", {
                 end: {line: 1, column: 18}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -2729,7 +2680,6 @@ test("x = { method(test) { } }", {
                 end: {line: 1, column: 17}
               }
             }],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -2738,7 +2688,6 @@ test("x = { method(test) { } }", {
                 end: {line: 1, column: 22}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -2812,7 +2761,6 @@ test("x = { 'method'() { } }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -2821,7 +2769,6 @@ test("x = { 'method'() { } }", {
                 end: {line: 1, column: 20}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -2894,7 +2841,6 @@ test("x = { get() { } }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -2903,7 +2849,6 @@ test("x = { get() { } }", {
                 end: {line: 1, column: 15}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -2976,7 +2921,6 @@ test("x = { set() { } }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -2985,7 +2929,6 @@ test("x = { set() { } }", {
                 end: {line: 1, column: 15}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -3058,7 +3001,6 @@ test("x = { method() 42 }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "Literal",
               value: 42,
@@ -3068,7 +3010,6 @@ test("x = { method() 42 }", {
                 end: {line: 1, column: 17}
               }
             },
-            rest: null,
             generator: false,
             expression: true,
             loc: {
@@ -3141,7 +3082,6 @@ test("x = { get method() 42 }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "Literal",
               value: 42,
@@ -3151,7 +3091,6 @@ test("x = { get method() 42 }", {
                 end: {line: 1, column: 21}
               }
             },
-            rest: null,
             generator: false,
             expression: true,
             loc: {
@@ -3231,7 +3170,6 @@ test("x = { set method(val) v = val }", {
                 end: {line: 1, column: 20}
               }
             }],
-            defaults: [],
             body: {
               type: "AssignmentExpression",
               operator: "=",
@@ -3256,7 +3194,6 @@ test("x = { set method(val) v = val }", {
                 end: {line: 1, column: 29}
               }
             },
-            rest: null,
             generator: false,
             expression: true,
             loc: {
@@ -4834,7 +4771,6 @@ test("export function parse() { }", {
         }
       },
       params: [],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [],
@@ -4843,7 +4779,6 @@ test("export function parse() { }", {
           end: {line: 1, column: 27}
         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -5615,7 +5550,6 @@ test("(function* () { yield v })", {
       type: "FunctionExpression",
       id: null,
       params: [],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [{
@@ -5646,7 +5580,6 @@ test("(function* () { yield v })", {
           end: {line: 1, column: 25}
         }
       },
-      rest: null,
       generator: true,
       expression: false,
       loc: {
@@ -5677,7 +5610,6 @@ test("(function* () { yield\nv })", {
       type: "FunctionExpression",
       id: null,
       params: [],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [
@@ -5718,7 +5650,6 @@ test("(function* () { yield\nv })", {
           end: {line: 2, column: 3}
         }
       },
-      rest: null,
       generator: true,
       expression: false,
       loc: {
@@ -5749,7 +5680,6 @@ test("(function* () { yield *v })", {
       type: "FunctionExpression",
       id: null,
       params: [],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [{
@@ -5780,7 +5710,6 @@ test("(function* () { yield *v })", {
           end: {line: 1, column: 26}
         }
       },
-      rest: null,
       generator: true,
       expression: false,
       loc: {
@@ -5816,7 +5745,6 @@ test("function* test () { yield *v }", {
       }
     },
     params: [],
-    defaults: [],
     body: {
       type: "BlockStatement",
       body: [{
@@ -5847,7 +5775,6 @@ test("function* test () { yield *v }", {
         end: {line: 1, column: 30}
       }
     },
-    rest: null,
     generator: true,
     expression: false,
     loc: {
@@ -5895,7 +5822,6 @@ test("var x = { *test () { yield *v } };", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [{
@@ -5926,7 +5852,6 @@ test("var x = { *test () { yield *v } };", {
                 end: {line: 1, column: 31}
               }
             },
-            rest: null,
             generator: true,
             expression: false,
             loc: {
@@ -5982,7 +5907,6 @@ test("function* t() {}", {
       }
     },
     params: [],
-    defaults: [],
     body: {
       type: "BlockStatement",
       body: [],
@@ -5991,7 +5915,6 @@ test("function* t() {}", {
         end: {line: 1, column: 16}
       }
     },
-    rest: null,
     generator: true,
     expression: false,
     loc: {
@@ -6017,7 +5940,6 @@ test("(function* () { yield yield 10 })", {
       type: "FunctionExpression",
       id: null,
       params: [],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [{
@@ -6057,7 +5979,6 @@ test("(function* () { yield yield 10 })", {
           end: {line: 1, column: 32}
         }
       },
-      rest: null,
       generator: true,
       expression: false,
       loc: {
@@ -6554,7 +6475,6 @@ test("class A {get() {}}", {
           type: "FunctionExpression",
           id: null,
           params: [],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -6563,7 +6483,6 @@ test("class A {get() {}}", {
               end: {line: 1, column: 17}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -6628,7 +6547,6 @@ test("class A { static get() {}}", {
           type: "FunctionExpression",
           id: null,
           params: [],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -6637,7 +6555,6 @@ test("class A { static get() {}}", {
               end: {line: 1, column: 25}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -6709,7 +6626,6 @@ test("class A extends B {get foo() {}}", {
           type: "FunctionExpression",
           id: null,
           params: [],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -6718,7 +6634,6 @@ test("class A extends B {get foo() {}}", {
               end: {line: 1, column: 31}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -6790,7 +6705,6 @@ test("class A extends B { static get foo() {}}", {
           type: "FunctionExpression",
           id: null,
           params: [],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -6799,7 +6713,6 @@ test("class A extends B { static get foo() {}}", {
               end: {line: 1, column: 39}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -6871,7 +6784,6 @@ test("class A {set a(v) {}}", {
               end: {line: 1, column: 16}
             }
           }],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -6880,7 +6792,6 @@ test("class A {set a(v) {}}", {
               end: {line: 1, column: 20}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -6952,7 +6863,6 @@ test("class A { static set a(v) {}}", {
               end: {line: 1, column: 24}
             }
           }],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -6961,7 +6871,6 @@ test("class A { static set a(v) {}}", {
               end: {line: 1, column: 28}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -7033,7 +6942,6 @@ test("class A {set(v) {};}", {
               end: {line: 1, column: 14}
             }
           }],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -7042,7 +6950,6 @@ test("class A {set(v) {};}", {
               end: {line: 1, column: 18}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -7114,7 +7021,6 @@ test("class A { static set(v) {};}", {
               end: {line: 1, column: 22}
             }
           }],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -7123,7 +7029,6 @@ test("class A { static set(v) {};}", {
               end: {line: 1, column: 26}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -7195,7 +7100,6 @@ test("class A {*gen(v) { yield v; }}", {
               end: {line: 1, column: 15}
             }
           }],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [{
@@ -7226,7 +7130,6 @@ test("class A {*gen(v) { yield v; }}", {
               end: {line: 1, column: 29}
             }
           },
-          rest: null,
           generator: true,
           expression: false,
           loc: {
@@ -7298,7 +7201,6 @@ test("class A { static *gen(v) { yield v; }}", {
               end: {line: 1, column: 23}
             }
           }],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [{
@@ -7329,7 +7231,6 @@ test("class A { static *gen(v) { yield v; }}", {
               end: {line: 1, column: 37}
             }
           },
-          rest: null,
           generator: true,
           expression: false,
           loc: {
@@ -7413,7 +7314,6 @@ test("\"use strict\"; (class A {constructor() { super() }})", {
               type: "FunctionExpression",
               id: null,
               params: [],
-              defaults: [],
               body: {
                 type: "BlockStatement",
                 body: [{
@@ -7444,7 +7344,6 @@ test("\"use strict\"; (class A {constructor() { super() }})", {
                   end: {line: 1, column: 49}
                 }
               },
-              rest: null,
               generator: false,
               expression: false,
               loc: {
@@ -7515,7 +7414,6 @@ test("class A {static foo() {}}", {
           type: "FunctionExpression",
           id: null,
           params: [],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -7524,7 +7422,6 @@ test("class A {static foo() {}}", {
               end: {line: 1, column: 24}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -7590,7 +7487,6 @@ test("class A {foo() {} static bar() {}}", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -7599,7 +7495,6 @@ test("class A {foo() {} static bar() {}}", {
                 end: {line: 1, column: 17}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -7629,7 +7524,6 @@ test("class A {foo() {} static bar() {}}", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -7638,7 +7532,6 @@ test("class A {foo() {} static bar() {}}", {
                 end: {line: 1, column: 33}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -7723,7 +7616,6 @@ test("\"use strict\"; (class A { static constructor() { super() }})", {
               type: "FunctionExpression",
               id: null,
               params: [],
-              defaults: [],
               body: {
                 type: "BlockStatement",
                 body: [{
@@ -7754,7 +7646,6 @@ test("\"use strict\"; (class A { static constructor() { super() }})", {
                   end: {line: 1, column: 57}
                 }
               },
-              rest: null,
               generator: false,
               expression: false,
               loc: {
@@ -7826,7 +7717,6 @@ test("class A { foo() {} bar() {}}", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -7835,7 +7725,6 @@ test("class A { foo() {} bar() {}}", {
                 end: {line: 1, column: 18}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -7865,7 +7754,6 @@ test("class A { foo() {} bar() {}}", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -7874,7 +7762,6 @@ test("class A { foo() {} bar() {}}", {
                 end: {line: 1, column: 27}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -7941,7 +7828,6 @@ test("class A { get foo() {} set foo(v) {}}", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -7950,7 +7836,6 @@ test("class A { get foo() {} set foo(v) {}}", {
                 end: {line: 1, column: 22}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -7987,7 +7872,6 @@ test("class A { get foo() {} set foo(v) {}}", {
                 end: {line: 1, column: 32}
               }
             }],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -7996,7 +7880,6 @@ test("class A { get foo() {} set foo(v) {}}", {
                 end: {line: 1, column: 36}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8063,7 +7946,6 @@ test("class A { static get foo() {} get foo() {}}", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8072,7 +7954,6 @@ test("class A { static get foo() {} get foo() {}}", {
                 end: {line: 1, column: 29}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8102,7 +7983,6 @@ test("class A { static get foo() {} get foo() {}}", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8111,7 +7991,6 @@ test("class A { static get foo() {} get foo() {}}", {
                 end: {line: 1, column: 42}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8178,7 +8057,6 @@ test("class A { static get foo() {} static get bar() {} }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8187,7 +8065,6 @@ test("class A { static get foo() {} static get bar() {} }", {
                 end: {line: 1, column: 29}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8217,7 +8094,6 @@ test("class A { static get foo() {} static get bar() {} }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8226,7 +8102,6 @@ test("class A { static get foo() {} static get bar() {} }", {
                 end: {line: 1, column: 49}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8293,7 +8168,6 @@ test("class A { static get foo() {} static set foo(v) {} get foo() {} set foo(v)
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8302,7 +8176,6 @@ test("class A { static get foo() {} static set foo(v) {} get foo() {} set foo(v)
                 end: {line: 1, column: 29}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8339,7 +8212,6 @@ test("class A { static get foo() {} static set foo(v) {} get foo() {} set foo(v)
                 end: {line: 1, column: 46}
               }
             }],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8348,7 +8220,6 @@ test("class A { static get foo() {} static set foo(v) {} get foo() {} set foo(v)
                 end: {line: 1, column: 50}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8378,7 +8249,6 @@ test("class A { static get foo() {} static set foo(v) {} get foo() {} set foo(v)
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8387,7 +8257,6 @@ test("class A { static get foo() {} static set foo(v) {} get foo() {} set foo(v)
                 end: {line: 1, column: 63}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8424,7 +8293,6 @@ test("class A { static get foo() {} static set foo(v) {} get foo() {} set foo(v)
                 end: {line: 1, column: 73}
               }
             }],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8433,7 +8301,6 @@ test("class A { static get foo() {} static set foo(v) {} get foo() {} set foo(v)
                 end: {line: 1, column: 77}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8522,8 +8389,6 @@ test("class A { static [foo]() {} }", {
           },
           id: null,
           params: [],
-          defaults: [],
-          rest: null,
           generator: false,
           body: {
             type: "BlockStatement",
@@ -8600,8 +8465,6 @@ test("class A { static get [foo]() {} }", {
           },
           id: null,
           params: [],
-          defaults: [],
-          rest: null,
           generator: false,
           body: {
             type: "BlockStatement",
@@ -8660,7 +8523,6 @@ test("class A { set foo(v) {} get foo() {} }", {
                 end: {line: 1, column: 19}
               }
             }],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8669,7 +8531,6 @@ test("class A { set foo(v) {} get foo() {} }", {
                 end: {line: 1, column: 23}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8699,7 +8560,6 @@ test("class A { set foo(v) {} get foo() {} }", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -8708,7 +8568,6 @@ test("class A { set foo(v) {} get foo() {} }", {
                 end: {line: 1, column: 36}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -8797,8 +8656,6 @@ test("class A { foo() {} get foo() {} }",{
             },
             id: null,
             params: [],
-            defaults: [],
-            rest: null,
             generator: false,
             body: {
               type: "BlockStatement",
@@ -8836,8 +8693,6 @@ test("class A { foo() {} get foo() {} }",{
             },
             id: null,
             params: [],
-            defaults: [],
-            rest: null,
             generator: false,
             body: {
               type: "BlockStatement",
@@ -9043,7 +8898,6 @@ test("({[x]: function() {}})", {
           type: "FunctionExpression",
           id: null,
           params: [],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -9052,7 +8906,6 @@ test("({[x]: function() {}})", {
               end: {line: 1, column: 20}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -9194,7 +9047,6 @@ test("({get [x]() {}, set [x](v) {}})", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -9203,7 +9055,6 @@ test("({get [x]() {}, set [x](v) {}})", {
                 end: {line: 1, column: 14}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -9241,7 +9092,6 @@ test("({get [x]() {}, set [x](v) {}})", {
                 end: {line: 1, column: 25}
               }
             }],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [],
@@ -9250,7 +9100,6 @@ test("({get [x]() {}, set [x](v) {}})", {
                 end: {line: 1, column: 29}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -9308,7 +9157,6 @@ test("({[x]() {}})", {
           type: "FunctionExpression",
           id: null,
           params: [],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -9317,7 +9165,6 @@ test("({[x]() {}})", {
               end: {line: 1, column: 10}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -9495,7 +9342,6 @@ test("function f({[x]: y}) {}", {
         end: {line: 1, column: 19}
       }
     }],
-    defaults: [],
     body: {
       type: "BlockStatement",
       body: [],
@@ -9504,7 +9350,6 @@ test("function f({[x]: y}) {}", {
         end: {line: 1, column: 23}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -9552,7 +9397,6 @@ test("var x = {*[test]() { yield *v; }}", {
             type: "FunctionExpression",
             id: null,
             params: [],
-            defaults: [],
             body: {
               type: "BlockStatement",
               body: [{
@@ -9583,7 +9427,6 @@ test("var x = {*[test]() { yield *v; }}", {
                 end: {line: 1, column: 32}
               }
             },
-            rest: null,
             generator: true,
             expression: false,
             loc: {
@@ -9678,8 +9521,6 @@ test("class A {[x]() {}}", {
           },
           id: null,
           params: [],
-          defaults: [],
-          rest: null,
           generator: false,
           body: {
             type: "BlockStatement",
@@ -9717,34 +9558,37 @@ test("function f([x] = [1]) {}", {
       }
     },
     params: [{
-      type: "ArrayPattern",
-      elements: [{
-        type: "Identifier",
-        name: "x",
+      type: "AssignmentPattern",
+      left: {
+        type: "ArrayPattern",
+        elements: [{
+          type: "Identifier",
+          name: "x",
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-    }],
-    defaults: [{
-      type: "ArrayExpression",
-      elements: [{
-        type: "Literal",
-        value: 1,
-        raw: "1",
+      },
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+        elements: [{
+          type: "Literal",
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+          raw: "1",
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@@ -9755,7 +9599,6 @@ test("function f([x] = [1]) {}", {
         end: {line: 1, column: 24}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -9786,72 +9629,75 @@ test("function f({x} = {x: 10}) {}", {
       }
     },
     params: [{
-      type: "ObjectPattern",
-      properties: [{
-        type: "Property",
-        key: {
-          type: "Identifier",
-          name: "x",
+      type: "AssignmentPattern",
+      left: {
+        type: "ObjectPattern",
+        properties: [{
+          type: "Property",
+          key: {
+            type: "Identifier",
+            name: "x",
+            loc: {
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+              end: {line: 1, column: 13}
+            }
+          },
+          value: {
+            type: "Identifier",
+            name: "x",
+            loc: {
+              start: {line: 1, column: 12},
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+            }
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+          shorthand: true,
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-            end: {line: 1, column: 13}
-          }
-        },
-        kind: "init",
-        method: false,
-        shorthand: true,
-        computed: false,
+        }],
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-          start: {line: 1, column: 12},
-          end: {line: 1, column: 13}
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-      type: "ObjectExpression",
-      properties: [{
-        type: "Property",
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+            }
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+            raw: "10",
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           }
-        },
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-        method: false,
-        shorthand: false,
-        computed: false,
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-          start: {line: 1, column: 18},
-          end: {line: 1, column: 23}
+          start: {line: 1, column: 17},
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-        end: {line: 1, column: 24}
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@@ -9862,7 +9708,6 @@ test("function f({x} = {x: 10}) {}", {
         end: {line: 1, column: 28}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -9899,72 +9744,75 @@ test("f = function({x} = {x: 10}) {}", {
         type: "FunctionExpression",
         id: null,
         params: [{
-          type: "ObjectPattern",
-          properties: [{
-            type: "Property",
-            key: {
-              type: "Identifier",
-              name: "x",
+          type: "AssignmentPattern",
+          left: {
+            type: "ObjectPattern",
+            properties: [{
+              type: "Property",
+              key: {
+                type: "Identifier",
+                name: "x",
+                loc: {
+                  start: {line: 1, column: 14},
+                  end: {line: 1, column: 15}
+                }
+              },
+              value: {
+                type: "Identifier",
+                name: "x",
+                loc: {
+                  start: {line: 1, column: 14},
+                  end: {line: 1, column: 15}
+                }
+              },
+              kind: "init",
+              method: false,
+              shorthand: true,
+              computed: false,
               loc: {
                 start: {line: 1, column: 14},
                 end: {line: 1, column: 15}
               }
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-                end: {line: 1, column: 15}
-              }
-            },
-            kind: "init",
-            method: false,
-            shorthand: true,
-            computed: false,
+            }],
             loc: {
-              start: {line: 1, column: 14},
-              end: {line: 1, column: 15}
+              start: {line: 1, column: 13},
+              end: {line: 1, column: 16}
             }
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-        defaults: [{
-          type: "ObjectExpression",
-          properties: [{
-            type: "Property",
-            key: {
-              type: "Identifier",
-              name: "x",
+          },
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+            type: "ObjectExpression",
+            properties: [{
+              type: "Property",
+              key: {
+                type: "Identifier",
+                name: "x",
+                loc: {
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+                  end: {line: 1, column: 21}
+                }
+              },
+              value: {
+                type: "Literal",
+                value: 10,
+                raw: "10",
+                loc: {
+                  start: {line: 1, column: 23},
+                  end: {line: 1, column: 25}
+                }
+              },
+              kind: "init",
+              method: false,
+              shorthand: false,
+              computed: false,
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                 end: {line: 1, column: 25}
               }
-            },
-            kind: "init",
-            method: false,
-            shorthand: false,
-            computed: false,
+            }],
             loc: {
-              start: {line: 1, column: 20},
-              end: {line: 1, column: 25}
+              start: {line: 1, column: 19},
+              end: {line: 1, column: 26}
             }
-          }],
-          loc: {
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@@ -9975,7 +9823,6 @@ test("f = function({x} = {x: 10}) {}", {
             end: {line: 1, column: 30}
           }
         },
-        rest: null,
         generator: false,
         expression: false,
         loc: {
@@ -10023,72 +9870,75 @@ test("({f: function({x} = {x: 10}) {}})", {
           type: "FunctionExpression",
           id: null,
           params: [{
-            type: "ObjectPattern",
-            properties: [{
-              type: "Property",
-              key: {
-                type: "Identifier",
-                name: "x",
+            type: "AssignmentPattern",
+            left: {
+              type: "ObjectPattern",
+              properties: [{
+                type: "Property",
+                key: {
+                  type: "Identifier",
+                  name: "x",
+                  loc: {
+                    start: {line: 1, column: 15},
+                    end: {line: 1, column: 16}
+                  }
+                },
+                value: {
+                  type: "Identifier",
+                  name: "x",
+                  loc: {
+                    start: {line: 1, column: 15},
+                    end: {line: 1, column: 16}
+                  }
+                },
+                kind: "init",
+                method: false,
+                shorthand: true,
+                computed: false,
                 loc: {
                   start: {line: 1, column: 15},
                   end: {line: 1, column: 16}
                 }
-              },
-              value: {
-                type: "Identifier",
-                name: "x",
-                loc: {
-                  start: {line: 1, column: 15},
-                  end: {line: 1, column: 16}
-                }
-              },
-              kind: "init",
-              method: false,
-              shorthand: true,
-              computed: false,
+              }],
               loc: {
-                start: {line: 1, column: 15},
-                end: {line: 1, column: 16}
+                start: {line: 1, column: 14},
+                end: {line: 1, column: 17}
               }
-            }],
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-              end: {line: 1, column: 17}
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-          defaults: [{
-            type: "ObjectExpression",
-            properties: [{
-              type: "Property",
-              key: {
-                type: "Identifier",
-                name: "x",
+            },
+            right: {
+              type: "ObjectExpression",
+              properties: [{
+                type: "Property",
+                key: {
+                  type: "Identifier",
+                  name: "x",
+                  loc: {
+                    start: {line: 1, column: 21},
+                    end: {line: 1, column: 22}
+                  }
+                },
+                value: {
+                  type: "Literal",
+                  value: 10,
+                  raw: "10",
+                  loc: {
+                    start: {line: 1, column: 24},
+                    end: {line: 1, column: 26}
+                  }
+                },
+                kind: "init",
+                method: false,
+                shorthand: false,
+                computed: false,
                 loc: {
                   start: {line: 1, column: 21},
-                  end: {line: 1, column: 22}
-                }
-              },
-              value: {
-                type: "Literal",
-                value: 10,
-                raw: "10",
-                loc: {
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                   end: {line: 1, column: 26}
                 }
-              },
-              kind: "init",
-              method: false,
-              shorthand: false,
-              computed: false,
+              }],
               loc: {
-                start: {line: 1, column: 21},
-                end: {line: 1, column: 26}
+                start: {line: 1, column: 20},
+                end: {line: 1, column: 27}
               }
-            }],
-            loc: {
-              start: {line: 1, column: 20},
-              end: {line: 1, column: 27}
             }
           }],
           body: {
@@ -10099,7 +9949,6 @@ test("({f: function({x} = {x: 10}) {}})", {
               end: {line: 1, column: 31}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -10156,72 +10005,75 @@ test("({f({x} = {x: 10}) {}})", {
           type: "FunctionExpression",
           id: null,
           params: [{
-            type: "ObjectPattern",
-            properties: [{
-              type: "Property",
-              key: {
-                type: "Identifier",
-                name: "x",
+            type: "AssignmentPattern",
+            left: {
+              type: "ObjectPattern",
+              properties: [{
+                type: "Property",
+                key: {
+                  type: "Identifier",
+                  name: "x",
+                  loc: {
+                    start: {line: 1, column: 5},
+                    end: {line: 1, column: 6}
+                  }
+                },
+                value: {
+                  type: "Identifier",
+                  name: "x",
+                  loc: {
+                    start: {line: 1, column: 5},
+                    end: {line: 1, column: 6}
+                  }
+                },
+                kind: "init",
+                method: false,
+                shorthand: true,
+                computed: false,
                 loc: {
                   start: {line: 1, column: 5},
                   end: {line: 1, column: 6}
                 }
-              },
-              value: {
-                type: "Identifier",
-                name: "x",
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-                  end: {line: 1, column: 6}
-                }
-              },
-              kind: "init",
-              method: false,
-              shorthand: true,
-              computed: false,
+              }],
               loc: {
-                start: {line: 1, column: 5},
-                end: {line: 1, column: 6}
+                start: {line: 1, column: 4},
+                end: {line: 1, column: 7}
               }
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-              end: {line: 1, column: 7}
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-          defaults: [{
-            type: "ObjectExpression",
-            properties: [{
-              type: "Property",
-              key: {
-                type: "Identifier",
-                name: "x",
+            },
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+              type: "ObjectExpression",
+              properties: [{
+                type: "Property",
+                key: {
+                  type: "Identifier",
+                  name: "x",
+                  loc: {
+                    start: {line: 1, column: 11},
+                    end: {line: 1, column: 12}
+                  }
+                },
+                value: {
+                  type: "Literal",
+                  value: 10,
+                  raw: "10",
+                  loc: {
+                    start: {line: 1, column: 14},
+                    end: {line: 1, column: 16}
+                  }
+                },
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+                computed: false,
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                   end: {line: 1, column: 16}
                 }
-              },
-              kind: "init",
-              method: false,
-              shorthand: false,
-              computed: false,
+              }],
               loc: {
-                start: {line: 1, column: 11},
-                end: {line: 1, column: 16}
+                start: {line: 1, column: 10},
+                end: {line: 1, column: 17}
               }
-            }],
-            loc: {
-              start: {line: 1, column: 10},
-              end: {line: 1, column: 17}
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           body: {
@@ -10232,7 +10084,6 @@ test("({f({x} = {x: 10}) {}})", {
               end: {line: 1, column: 21}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -10293,72 +10144,75 @@ test("(class {f({x} = {x: 10}) {}})", {
             type: "FunctionExpression",
             id: null,
             params: [{
-              type: "ObjectPattern",
-              properties: [{
-                type: "Property",
-                key: {
-                  type: "Identifier",
-                  name: "x",
+              type: "AssignmentPattern",
+              left: {
+                type: "ObjectPattern",
+                properties: [{
+                  type: "Property",
+                  key: {
+                    type: "Identifier",
+                    name: "x",
+                    loc: {
+                      start: {line: 1, column: 11},
+                      end: {line: 1, column: 12}
+                    }
+                  },
+                  value: {
+                    type: "Identifier",
+                    name: "x",
+                    loc: {
+                      start: {line: 1, column: 11},
+                      end: {line: 1, column: 12}
+                    }
+                  },
+                  kind: "init",
+                  method: false,
+                  shorthand: true,
+                  computed: false,
                   loc: {
                     start: {line: 1, column: 11},
                     end: {line: 1, column: 12}
                   }
-                },
-                value: {
-                  type: "Identifier",
-                  name: "x",
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-                    end: {line: 1, column: 12}
-                  }
-                },
-                kind: "init",
-                method: false,
-                shorthand: true,
-                computed: false,
+                }],
                 loc: {
-                  start: {line: 1, column: 11},
-                  end: {line: 1, column: 12}
+                  start: {line: 1, column: 10},
+                  end: {line: 1, column: 13}
                 }
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-            defaults: [{
-              type: "ObjectExpression",
-              properties: [{
-                type: "Property",
-                key: {
-                  type: "Identifier",
-                  name: "x",
+              },
+              right: {
+                type: "ObjectExpression",
+                properties: [{
+                  type: "Property",
+                  key: {
+                    type: "Identifier",
+                    name: "x",
+                    loc: {
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+                      end: {line: 1, column: 18}
+                    }
+                  },
+                  value: {
+                    type: "Literal",
+                    value: 10,
+                    raw: "10",
+                    loc: {
+                      start: {line: 1, column: 20},
+                      end: {line: 1, column: 22}
+                    }
+                  },
+                  kind: "init",
+                  method: false,
+                  shorthand: false,
+                  computed: false,
                   loc: {
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-                    end: {line: 1, column: 18}
-                  }
-                },
-                value: {
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-                  value: 10,
-                  raw: "10",
-                  loc: {
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                     end: {line: 1, column: 22}
                   }
-                },
-                kind: "init",
-                method: false,
-                shorthand: false,
-                computed: false,
+                }],
                 loc: {
-                  start: {line: 1, column: 17},
-                  end: {line: 1, column: 22}
+                  start: {line: 1, column: 16},
+                  end: {line: 1, column: 23}
                 }
-              }],
-              loc: {
-                start: {line: 1, column: 16},
-                end: {line: 1, column: 23}
               }
             }],
             body: {
@@ -10369,7 +10223,6 @@ test("(class {f({x} = {x: 10}) {}})", {
                 end: {line: 1, column: 27}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -10417,72 +10270,75 @@ test("(({x} = {x: 10}) => {})", {
       type: "ArrowFunctionExpression",
       id: null,
       params: [{
-        type: "ObjectPattern",
-        properties: [{
-          type: "Property",
-          key: {
-            type: "Identifier",
-            name: "x",
+        type: "AssignmentPattern",
+        left: {
+          type: "ObjectPattern",
+          properties: [{
+            type: "Property",
+            key: {
+              type: "Identifier",
+              name: "x",
+              loc: {
+                start: {line: 1, column: 3},
+                end: {line: 1, column: 4}
+              }
+            },
+            value: {
+              type: "Identifier",
+              name: "x",
+              loc: {
+                start: {line: 1, column: 3},
+                end: {line: 1, column: 4}
+              }
+            },
+            kind: "init",
+            method: false,
+            shorthand: true,
+            computed: false,
             loc: {
               start: {line: 1, column: 3},
               end: {line: 1, column: 4}
             }
-          },
-          value: {
-            type: "Identifier",
-            name: "x",
-            loc: {
-              start: {line: 1, column: 3},
-              end: {line: 1, column: 4}
-            }
-          },
-          kind: "init",
-          method: false,
-          shorthand: true,
-          computed: false,
+          }],
           loc: {
-            start: {line: 1, column: 3},
-            end: {line: 1, column: 4}
+            start: {line: 1, column: 2},
+            end: {line: 1, column: 5}
           }
-        }],
-        loc: {
-          start: {line: 1, column: 2},
-          end: {line: 1, column: 5}
-        }
-      }],
-      defaults: [{
-        type: "ObjectExpression",
-        properties: [{
-          type: "Property",
-          key: {
-            type: "Identifier",
-            name: "x",
+        },
+        right: {
+          type: "ObjectExpression",
+          properties: [{
+            type: "Property",
+            key: {
+              type: "Identifier",
+              name: "x",
+              loc: {
+                start: {line: 1, column: 9},
+                end: {line: 1, column: 10}
+              }
+            },
+            value: {
+              type: "Literal",
+              value: 10,
+              raw: "10",
+              loc: {
+                start: {line: 1, column: 12},
+                end: {line: 1, column: 14}
+              }
+            },
+            kind: "init",
+            method: false,
+            shorthand: false,
+            computed: false,
             loc: {
               start: {line: 1, column: 9},
-              end: {line: 1, column: 10}
-            }
-          },
-          value: {
-            type: "Literal",
-            value: 10,
-            raw: "10",
-            loc: {
-              start: {line: 1, column: 12},
               end: {line: 1, column: 14}
             }
-          },
-          kind: "init",
-          method: false,
-          shorthand: false,
-          computed: false,
+          }],
           loc: {
-            start: {line: 1, column: 9},
-            end: {line: 1, column: 14}
+            start: {line: 1, column: 8},
+            end: {line: 1, column: 15}
           }
-        }],
-        loc: {
-          start: {line: 1, column: 8},
-          end: {line: 1, column: 15}
         }
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@@ -10493,7 +10349,6 @@ test("(({x} = {x: 10}) => {})", {
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         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -10535,20 +10390,23 @@ test("x = function(y = 1) {}", {
         type: "FunctionExpression",
         id: null,
         params: [{
-          type: "Identifier",
-          name: "y",
-          loc: {
-            start: {line: 1, column: 13},
-            end: {line: 1, column: 14}
-          }
-        }],
-        defaults: [{
-          type: "Literal",
-          value: 1,
-          raw: "1",
-          loc: {
-            start: {line: 1, column: 17},
-            end: {line: 1, column: 18}
+          type: "AssignmentPattern",
+          left: {
+            type: "Identifier",
+            name: "y",
+            loc: {
+              start: {line: 1, column: 13},
+              end: {line: 1, column: 14}
+            }
+          },
+          right: {
+            type: "Literal",
+            value: 1,
+            raw: "1",
+            loc: {
+              start: {line: 1, column: 17},
+              end: {line: 1, column: 18}
+            }
           }
         }],
         body: {
@@ -10559,7 +10417,6 @@ test("x = function(y = 1) {}", {
             end: {line: 1, column: 22}
           }
         },
-        rest: null,
         generator: false,
         expression: false,
         loc: {
@@ -10600,20 +10457,23 @@ test("function f(a = 1) {}", {
       }
     },
     params: [{
-      type: "Identifier",
-      name: "a",
-      loc: {
-        start: {line: 1, column: 11},
-        end: {line: 1, column: 12}
-      }
-    }],
-    defaults: [{
-      type: "Literal",
-      value: 1,
-      raw: "1",
-      loc: {
-        start: {line: 1, column: 15},
-        end: {line: 1, column: 16}
+      type: "AssignmentPattern",
+      left: {
+        type: "Identifier",
+        name: "a",
+        loc: {
+          start: {line: 1, column: 11},
+          end: {line: 1, column: 12}
+        }
+      },
+      right: {
+        type: "Literal",
+        value: 1,
+        raw: "1",
+        loc: {
+          start: {line: 1, column: 15},
+          end: {line: 1, column: 16}
+        }
       }
     }],
     body: {
@@ -10624,7 +10484,6 @@ test("function f(a = 1) {}", {
         end: {line: 1, column: 20}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -10673,20 +10532,23 @@ test("x = { f: function(a=1) {} }", {
             type: "FunctionExpression",
             id: null,
             params: [{
-              type: "Identifier",
-              name: "a",
-              loc: {
-                start: {line: 1, column: 18},
-                end: {line: 1, column: 19}
-              }
-            }],
-            defaults: [{
-              type: "Literal",
-              value: 1,
-              raw: "1",
-              loc: {
-                start: {line: 1, column: 20},
-                end: {line: 1, column: 21}
+              type: "AssignmentPattern",
+              left: {
+                type: "Identifier",
+                name: "a",
+                loc: {
+                  start: {line: 1, column: 18},
+                  end: {line: 1, column: 19}
+                }
+              },
+              right: {
+                type: "Literal",
+                value: 1,
+                raw: "1",
+                loc: {
+                  start: {line: 1, column: 20},
+                  end: {line: 1, column: 21}
+                }
               }
             }],
             body: {
@@ -10697,7 +10559,6 @@ test("x = { f: function(a=1) {} }", {
                 end: {line: 1, column: 25}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -10770,20 +10631,23 @@ test("x = { f(a=1) {} }", {
             type: "FunctionExpression",
             id: null,
             params: [{
-              type: "Identifier",
-              name: "a",
-              loc: {
-                start: {line: 1, column: 8},
-                end: {line: 1, column: 9}
-              }
-            }],
-            defaults: [{
-              type: "Literal",
-              value: 1,
-              raw: "1",
-              loc: {
-                start: {line: 1, column: 10},
-                end: {line: 1, column: 11}
+              type: "AssignmentPattern",
+              left: {
+                type: "Identifier",
+                name: "a",
+                loc: {
+                  start: {line: 1, column: 8},
+                  end: {line: 1, column: 9}
+                }
+              },
+              right: {
+                type: "Literal",
+                value: 1,
+                raw: "1",
+                loc: {
+                  start: {line: 1, column: 10},
+                  end: {line: 1, column: 11}
+                }
               }
             }],
             body: {
@@ -10794,7 +10658,6 @@ test("x = { f(a=1) {} }", {
                 end: {line: 1, column: 15}
               }
             },
-            rest: null,
             generator: false,
             expression: false,
             loc: {
@@ -10850,15 +10713,27 @@ test("function f(a, ...b) {}", {
         end: {line: 1, column: 10}
       }
     },
-    params: [{
-      type: "Identifier",
-      name: "a",
-      loc: {
-        start: {line: 1, column: 11},
-        end: {line: 1, column: 12}
+    params: [
+      {
+        type: "Identifier",
+        name: "a",
+        loc: {
+          start: {line: 1, column: 11},
+          end: {line: 1, column: 12}
+        }
+      },
+      {
+        type: "RestElement",
+        argument: {
+          type: "Identifier",
+          name: "b",
+          loc: {
+            start: {line: 1, column: 17},
+            end: {line: 1, column: 18}
+          }
+        }
       }
-    }],
-    defaults: [],
+    ],
     body: {
       type: "BlockStatement",
       body: [],
@@ -10867,14 +10742,6 @@ test("function f(a, ...b) {}", {
         end: {line: 1, column: 22}
       }
     },
-    rest: {
-      type: "Identifier",
-      name: "b",
-      loc: {
-        start: {line: 1, column: 17},
-        end: {line: 1, column: 18}
-      }
-    },
     generator: false,
     expression: false,
     loc: {
@@ -10931,7 +10798,6 @@ test("function x([ a, b ]){}", {
         end: {line: 1, column: 19}
       }
     }],
-    defaults: [],
     body: {
       type: "BlockStatement",
       body: [],
@@ -10940,7 +10806,6 @@ test("function x([ a, b ]){}", {
         end: {line: 1, column: 22}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -11033,7 +10898,6 @@ test("function x({ a, b }){}", {
         end: {line: 1, column: 19}
       }
     }],
-    defaults: [],
     body: {
       type: "BlockStatement",
       body: [],
@@ -11042,7 +10906,6 @@ test("function x({ a, b }){}", {
         end: {line: 1, column: 22}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -11116,7 +10979,6 @@ test("function x(a, { a }){}", {
         }
       }
     ],
-    defaults: [],
     body: {
       type: "BlockStatement",
       body: [],
@@ -11125,7 +10987,6 @@ test("function x(a, { a }){}", {
         end: {line: 1, column: 22}
       }
     },
-    rest: null,
     generator: false,
     expression: false,
     loc: {
@@ -11155,8 +11016,34 @@ test("function x(...[ a, b ]){}", {
         end: {line: 1, column: 10}
       }
     },
-    params: [],
-    defaults: [],
+    params: [{
+      type: "RestElement",
+      argument: {
+        type: "ArrayPattern",
+        elements: [
+          {
+            type: "Identifier",
+            name: "a",
+            loc: {
+              start: {line: 1, column: 16},
+              end: {line: 1, column: 17}
+            }
+          },
+          {
+            type: "Identifier",
+            name: "b",
+            loc: {
+              start: {line: 1, column: 19},
+              end: {line: 1, column: 20}
+            }
+          }
+        ],
+        loc: {
+          start: {line: 1, column: 14},
+          end: {line: 1, column: 22}
+        }
+      }
+    }],
     body: {
       type: "BlockStatement",
       body: [],
@@ -11165,31 +11052,6 @@ test("function x(...[ a, b ]){}", {
         end: {line: 1, column: 25}
       }
     },
-    rest: {
-      type: "ArrayPattern",
-      elements: [
-        {
-          type: "Identifier",
-          name: "a",
-          loc: {
-            start: {line: 1, column: 16},
-            end: {line: 1, column: 17}
-          }
-        },
-        {
-          type: "Identifier",
-          name: "b",
-          loc: {
-            start: {line: 1, column: 19},
-            end: {line: 1, column: 20}
-          }
-        }
-      ],
-      loc: {
-        start: {line: 1, column: 14},
-        end: {line: 1, column: 22}
-      }
-    },
     generator: false,
     expression: false,
     loc: {
@@ -11219,142 +11081,179 @@ test("function x({ a: { w, x }, b: [y, z] }, ...[a, b, c]){}", {
         end: {line: 1, column: 10}
       }
     },
-    params: [{
-      type: "ObjectPattern",
-      properties: [
-        {
-          type: "Property",
-          key: {
-            type: "Identifier",
-            name: "a",
+    params: [
+      {
+        type: "ObjectPattern",
+        properties: [
+          {
+            type: "Property",
+            key: {
+              type: "Identifier",
+              name: "a",
+              loc: {
+                start: {line: 1, column: 13},
+                end: {line: 1, column: 14}
+              }
+            },
+            value: {
+              type: "ObjectPattern",
+              properties: [
+                {
+                  type: "Property",
+                  key: {
+                    type: "Identifier",
+                    name: "w",
+                    loc: {
+                      start: {line: 1, column: 18},
+                      end: {line: 1, column: 19}
+                    }
+                  },
+                  value: {
+                    type: "Identifier",
+                    name: "w",
+                    loc: {
+                      start: {line: 1, column: 18},
+                      end: {line: 1, column: 19}
+                    }
+                  },
+                  kind: "init",
+                  method: false,
+                  shorthand: true,
+                  computed: false,
+                  loc: {
+                    start: {line: 1, column: 18},
+                    end: {line: 1, column: 19}
+                  }
+                },
+                {
+                  type: "Property",
+                  key: {
+                    type: "Identifier",
+                    name: "x",
+                    loc: {
+                      start: {line: 1, column: 21},
+                      end: {line: 1, column: 22}
+                    }
+                  },
+                  value: {
+                    type: "Identifier",
+                    name: "x",
+                    loc: {
+                      start: {line: 1, column: 21},
+                      end: {line: 1, column: 22}
+                    }
+                  },
+                  kind: "init",
+                  method: false,
+                  shorthand: true,
+                  computed: false,
+                  loc: {
+                    start: {line: 1, column: 21},
+                    end: {line: 1, column: 22}
+                  }
+                }
+              ],
+              loc: {
+                start: {line: 1, column: 16},
+                end: {line: 1, column: 24}
+              }
+            },
+            kind: "init",
+            method: false,
+            shorthand: false,
+            computed: false,
             loc: {
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-              end: {line: 1, column: 14}
-            }
-          },
-          value: {
-            type: "ObjectPattern",
-            properties: [
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-                type: "Property",
-                key: {
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-                    end: {line: 1, column: 19}
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-                    end: {line: 1, column: 19}
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-                method: false,
-                shorthand: true,
-                computed: false,
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-                  end: {line: 1, column: 19}
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-                    end: {line: 1, column: 22}
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-                    end: {line: 1, column: 22}
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-                kind: "init",
-                method: false,
-                shorthand: true,
-                computed: false,
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-                  end: {line: 1, column: 22}
-                }
-              }
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-          method: false,
-          shorthand: false,
-          computed: false,
-          loc: {
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-            end: {line: 1, column: 24}
-          }
-        },
-        {
-          type: "Property",
-          key: {
-            type: "Identifier",
-            name: "b",
+          {
+            type: "Property",
+            key: {
+              type: "Identifier",
+              name: "b",
+              loc: {
+                start: {line: 1, column: 26},
+                end: {line: 1, column: 27}
+              }
+            },
+            value: {
+              type: "ArrayPattern",
+              elements: [
+                {
+                  type: "Identifier",
+                  name: "y",
+                  loc: {
+                    start: {line: 1, column: 30},
+                    end: {line: 1, column: 31}
+                  }
+                },
+                {
+                  type: "Identifier",
+                  name: "z",
+                  loc: {
+                    start: {line: 1, column: 33},
+                    end: {line: 1, column: 34}
+                  }
+                }
+              ],
+              loc: {
+                start: {line: 1, column: 29},
+                end: {line: 1, column: 35}
+              }
+            },
+            kind: "init",
+            method: false,
+            shorthand: false,
+            computed: false,
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-              end: {line: 1, column: 27}
-            }
-          },
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-            elements: [
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-                type: "Identifier",
-                name: "y",
-                loc: {
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-              }
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               end: {line: 1, column: 35}
             }
-          },
-          kind: "init",
-          method: false,
-          shorthand: false,
-          computed: false,
+          }
+        ],
+        loc: {
+          start: {line: 1, column: 11},
+          end: {line: 1, column: 37}
+        }
+      },
+      {
+        type: "RestElement",
+        argument: {
+          type: "ArrayPattern",
+          elements: [
+            {
+              type: "Identifier",
+              name: "a",
+              loc: {
+                start: {line: 1, column: 43},
+                end: {line: 1, column: 44}
+              }
+            },
+            {
+              type: "Identifier",
+              name: "b",
+              loc: {
+                start: {line: 1, column: 46},
+                end: {line: 1, column: 47}
+              }
+            },
+            {
+              type: "Identifier",
+              name: "c",
+              loc: {
+                start: {line: 1, column: 49},
+                end: {line: 1, column: 50}
+              }
+            }
+          ],
           loc: {
-            start: {line: 1, column: 26},
-            end: {line: 1, column: 35}
+            start: {line: 1, column: 42},
+            end: {line: 1, column: 51}
           }
         }
-      ],
-      loc: {
-        start: {line: 1, column: 11},
-        end: {line: 1, column: 37}
       }
-    }],
-    defaults: [],
+    ],
     body: {
       type: "BlockStatement",
       body: [],
@@ -11363,39 +11262,6 @@ test("function x({ a: { w, x }, b: [y, z] }, ...[a, b, c]){}", {
         end: {line: 1, column: 54}
       }
     },
-    rest: {
-      type: "ArrayPattern",
-      elements: [
-        {
-          type: "Identifier",
-          name: "a",
-          loc: {
-            start: {line: 1, column: 43},
-            end: {line: 1, column: 44}
-          }
-        },
-        {
-          type: "Identifier",
-          name: "b",
-          loc: {
-            start: {line: 1, column: 46},
-            end: {line: 1, column: 47}
-          }
-        },
-        {
-          type: "Identifier",
-          name: "c",
-          loc: {
-            start: {line: 1, column: 49},
-            end: {line: 1, column: 50}
-          }
-        }
-      ],
-      loc: {
-        start: {line: 1, column: 42},
-        end: {line: 1, column: 51}
-      }
-    },
     generator: false,
     expression: false,
     loc: {
@@ -11452,7 +11318,6 @@ test("(function x([ a, b ]){})", {
           end: {line: 1, column: 20}
         }
       }],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [],
@@ -11461,7 +11326,6 @@ test("(function x([ a, b ]){})", {
           end: {line: 1, column: 23}
         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -11561,7 +11425,6 @@ test("(function x({ a, b }){})", {
           end: {line: 1, column: 20}
         }
       }],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [],
@@ -11570,7 +11433,6 @@ test("(function x({ a, b }){})", {
           end: {line: 1, column: 23}
         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -11607,8 +11469,34 @@ test("(function x(...[ a, b ]){})", {
           end: {line: 1, column: 11}
         }
       },
-      params: [],
-      defaults: [],
+      params: [{
+        type: "RestElement",
+        argument: {
+          type: "ArrayPattern",
+          elements: [
+            {
+              type: "Identifier",
+              name: "a",
+              loc: {
+                start: {line: 1, column: 17},
+                end: {line: 1, column: 18}
+              }
+            },
+            {
+              type: "Identifier",
+              name: "b",
+              loc: {
+                start: {line: 1, column: 20},
+                end: {line: 1, column: 21}
+              }
+            }
+          ],
+          loc: {
+            start: {line: 1, column: 15},
+            end: {line: 1, column: 23}
+          }
+        }
+      }],
       body: {
         type: "BlockStatement",
         body: [],
@@ -11617,31 +11505,6 @@ test("(function x(...[ a, b ]){})", {
           end: {line: 1, column: 26}
         }
       },
-      rest: {
-        type: "ArrayPattern",
-        elements: [
-          {
-            type: "Identifier",
-            name: "a",
-            loc: {
-              start: {line: 1, column: 17},
-              end: {line: 1, column: 18}
-            }
-          },
-          {
-            type: "Identifier",
-            name: "b",
-            loc: {
-              start: {line: 1, column: 20},
-              end: {line: 1, column: 21}
-            }
-          }
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-        loc: {
-          start: {line: 1, column: 15},
-          end: {line: 1, column: 23}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -11678,142 +11541,179 @@ test("(function x({ a: { w, x }, b: [y, z] }, ...[a, b, c]){})", {
           end: {line: 1, column: 11}
         }
       },
-      params: [{
-        type: "ObjectPattern",
-        properties: [
-          {
-            type: "Property",
-            key: {
-              type: "Identifier",
-              name: "a",
+      params: [
+        {
+          type: "ObjectPattern",
+          properties: [
+            {
+              type: "Property",
+              key: {
+                type: "Identifier",
+                name: "a",
+                loc: {
+                  start: {line: 1, column: 14},
+                  end: {line: 1, column: 15}
+                }
+              },
+              value: {
+                type: "ObjectPattern",
+                properties: [
+                  {
+                    type: "Property",
+                    key: {
+                      type: "Identifier",
+                      name: "w",
+                      loc: {
+                        start: {line: 1, column: 19},
+                        end: {line: 1, column: 20}
+                      }
+                    },
+                    value: {
+                      type: "Identifier",
+                      name: "w",
+                      loc: {
+                        start: {line: 1, column: 19},
+                        end: {line: 1, column: 20}
+                      }
+                    },
+                    kind: "init",
+                    method: false,
+                    shorthand: true,
+                    computed: false,
+                    loc: {
+                      start: {line: 1, column: 19},
+                      end: {line: 1, column: 20}
+                    }
+                  },
+                  {
+                    type: "Property",
+                    key: {
+                      type: "Identifier",
+                      name: "x",
+                      loc: {
+                        start: {line: 1, column: 22},
+                        end: {line: 1, column: 23}
+                      }
+                    },
+                    value: {
+                      type: "Identifier",
+                      name: "x",
+                      loc: {
+                        start: {line: 1, column: 22},
+                        end: {line: 1, column: 23}
+                      }
+                    },
+                    kind: "init",
+                    method: false,
+                    shorthand: true,
+                    computed: false,
+                    loc: {
+                      start: {line: 1, column: 22},
+                      end: {line: 1, column: 23}
+                    }
+                  }
+                ],
+                loc: {
+                  start: {line: 1, column: 17},
+                  end: {line: 1, column: 25}
+                }
+              },
+              kind: "init",
+              method: false,
+              shorthand: false,
+              computed: false,
               loc: {
                 start: {line: 1, column: 14},
-                end: {line: 1, column: 15}
-              }
-            },
-            value: {
-              type: "ObjectPattern",
-              properties: [
-                {
-                  type: "Property",
-                  key: {
-                    type: "Identifier",
-                    name: "w",
-                    loc: {
-                      start: {line: 1, column: 19},
-                      end: {line: 1, column: 20}
-                    }
-                  },
-                  value: {
-                    type: "Identifier",
-                    name: "w",
-                    loc: {
-                      start: {line: 1, column: 19},
-                      end: {line: 1, column: 20}
-                    }
-                  },
-                  kind: "init",
-                  method: false,
-                  shorthand: true,
-                  computed: false,
-                  loc: {
-                    start: {line: 1, column: 19},
-                    end: {line: 1, column: 20}
-                  }
-                },
-                {
-                  type: "Property",
-                  key: {
-                    type: "Identifier",
-                    name: "x",
-                    loc: {
-                      start: {line: 1, column: 22},
-                      end: {line: 1, column: 23}
-                    }
-                  },
-                  value: {
-                    type: "Identifier",
-                    name: "x",
-                    loc: {
-                      start: {line: 1, column: 22},
-                      end: {line: 1, column: 23}
-                    }
-                  },
-                  kind: "init",
-                  method: false,
-                  shorthand: true,
-                  computed: false,
-                  loc: {
-                    start: {line: 1, column: 22},
-                    end: {line: 1, column: 23}
-                  }
-                }
-              ],
-              loc: {
-                start: {line: 1, column: 17},
                 end: {line: 1, column: 25}
               }
             },
-            kind: "init",
-            method: false,
-            shorthand: false,
-            computed: false,
-            loc: {
-              start: {line: 1, column: 14},
-              end: {line: 1, column: 25}
-            }
-          },
-          {
-            type: "Property",
-            key: {
-              type: "Identifier",
-              name: "b",
+            {
+              type: "Property",
+              key: {
+                type: "Identifier",
+                name: "b",
+                loc: {
+                  start: {line: 1, column: 27},
+                  end: {line: 1, column: 28}
+                }
+              },
+              value: {
+                type: "ArrayPattern",
+                elements: [
+                  {
+                    type: "Identifier",
+                    name: "y",
+                    loc: {
+                      start: {line: 1, column: 31},
+                      end: {line: 1, column: 32}
+                    }
+                  },
+                  {
+                    type: "Identifier",
+                    name: "z",
+                    loc: {
+                      start: {line: 1, column: 34},
+                      end: {line: 1, column: 35}
+                    }
+                  }
+                ],
+                loc: {
+                  start: {line: 1, column: 30},
+                  end: {line: 1, column: 36}
+                }
+              },
+              kind: "init",
+              method: false,
+              shorthand: false,
+              computed: false,
               loc: {
                 start: {line: 1, column: 27},
-                end: {line: 1, column: 28}
-              }
-            },
-            value: {
-              type: "ArrayPattern",
-              elements: [
-                {
-                  type: "Identifier",
-                  name: "y",
-                  loc: {
-                    start: {line: 1, column: 31},
-                    end: {line: 1, column: 32}
-                  }
-                },
-                {
-                  type: "Identifier",
-                  name: "z",
-                  loc: {
-                    start: {line: 1, column: 34},
-                    end: {line: 1, column: 35}
-                  }
-                }
-              ],
-              loc: {
-                start: {line: 1, column: 30},
                 end: {line: 1, column: 36}
               }
-            },
-            kind: "init",
-            method: false,
-            shorthand: false,
-            computed: false,
+            }
+          ],
+          loc: {
+            start: {line: 1, column: 12},
+            end: {line: 1, column: 38}
+          }
+        },
+        {
+          type: "RestElement",
+          argument: {
+            type: "ArrayPattern",
+            elements: [
+              {
+                type: "Identifier",
+                name: "a",
+                loc: {
+                  start: {line: 1, column: 44},
+                  end: {line: 1, column: 45}
+                }
+              },
+              {
+                type: "Identifier",
+                name: "b",
+                loc: {
+                  start: {line: 1, column: 47},
+                  end: {line: 1, column: 48}
+                }
+              },
+              {
+                type: "Identifier",
+                name: "c",
+                loc: {
+                  start: {line: 1, column: 50},
+                  end: {line: 1, column: 51}
+                }
+              }
+            ],
             loc: {
-              start: {line: 1, column: 27},
-              end: {line: 1, column: 36}
+              start: {line: 1, column: 43},
+              end: {line: 1, column: 52}
             }
           }
-        ],
-        loc: {
-          start: {line: 1, column: 12},
-          end: {line: 1, column: 38}
         }
-      }],
-      defaults: [],
+      ],
       body: {
         type: "BlockStatement",
         body: [],
@@ -11822,39 +11722,6 @@ test("(function x({ a: { w, x }, b: [y, z] }, ...[a, b, c]){})", {
           end: {line: 1, column: 55}
         }
       },
-      rest: {
-        type: "ArrayPattern",
-        elements: [
-          {
-            type: "Identifier",
-            name: "a",
-            loc: {
-              start: {line: 1, column: 44},
-              end: {line: 1, column: 45}
-            }
-          },
-          {
-            type: "Identifier",
-            name: "b",
-            loc: {
-              start: {line: 1, column: 47},
-              end: {line: 1, column: 48}
-            }
-          },
-          {
-            type: "Identifier",
-            name: "c",
-            loc: {
-              start: {line: 1, column: 50},
-              end: {line: 1, column: 51}
-            }
-          }
-        ],
-        loc: {
-          start: {line: 1, column: 43},
-          end: {line: 1, column: 52}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -11921,7 +11788,6 @@ test("({ x([ a, b ]){} })", {
               end: {line: 1, column: 13}
             }
           }],
-          defaults: [],
           body: {
             type: "BlockStatement",
             body: [],
@@ -11930,7 +11796,6 @@ test("({ x([ a, b ]){} })", {
               end: {line: 1, column: 16}
             }
           },
-          rest: null,
           generator: false,
           expression: false,
           loc: {
@@ -11986,8 +11851,34 @@ test("({ x(...[ a, b ]){} })", {
         value: {
           type: "FunctionExpression",
           id: null,
-          params: [],
-          defaults: [],
+          params: [{
+            type: "RestElement",
+            argument: {
+              type: "ArrayPattern",
+              elements: [
+                {
+                  type: "Identifier",
+                  name: "a",
+                  loc: {
+                    start: {line: 1, column: 10},
+                    end: {line: 1, column: 11}
+                  }
+                },
+                {
+                  type: "Identifier",
+                  name: "b",
+                  loc: {
+                    start: {line: 1, column: 13},
+                    end: {line: 1, column: 14}
+                  }
+                }
+              ],
+              loc: {
+                start: {line: 1, column: 8},
+                end: {line: 1, column: 16}
+              }
+            }
+          }],
           body: {
             type: "BlockStatement",
             body: [],
@@ -11996,31 +11887,6 @@ test("({ x(...[ a, b ]){} })", {
               end: {line: 1, column: 19}
             }
           },
-          rest: {
-            type: "ArrayPattern",
-            elements: [
-              {
-                type: "Identifier",
-                name: "a",
-                loc: {
-                  start: {line: 1, column: 10},
-                  end: {line: 1, column: 11}
-                }
-              },
-              {
-                type: "Identifier",
-                name: "b",
-                loc: {
-                  start: {line: 1, column: 13},
-                  end: {line: 1, column: 14}
-                }
-              }
-            ],
-            loc: {
-              start: {line: 1, column: 8},
-              end: {line: 1, column: 16}
-            }
-          },
           generator: false,
           expression: false,
           loc: {
@@ -12076,7 +11942,8 @@ test("({ x({ a: { w, x }, b: [y, z] }, ...[a, b, c]){} })", {
         value: {
           type: "FunctionExpression",
           id: null,
-          params: [{
+          params: [
+          {
             type: "ObjectPattern",
             properties: [
               {
@@ -12210,8 +12077,44 @@ test("({ x({ a: { w, x }, b: [y, z] }, ...[a, b, c]){} })", {
               start: {line: 1, column: 5},
               end: {line: 1, column: 31}
             }
-          }],
-          defaults: [],
+          },
+          {
+            type: "RestElement",
+            argument: {
+              type: "ArrayPattern",
+              elements: [
+                {
+                  type: "Identifier",
+                  name: "a",
+                  loc: {
+                    start: {line: 1, column: 37},
+                    end: {line: 1, column: 38}
+                  }
+                },
+                {
+                  type: "Identifier",
+                  name: "b",
+                  loc: {
+                    start: {line: 1, column: 40},
+                    end: {line: 1, column: 41}
+                  }
+                },
+                {
+                  type: "Identifier",
+                  name: "c",
+                  loc: {
+                    start: {line: 1, column: 43},
+                    end: {line: 1, column: 44}
+                  }
+                }
+              ],
+              loc: {
+                start: {line: 1, column: 36},
+                end: {line: 1, column: 45}
+              }
+            }
+          }
+          ],
           body: {
             type: "BlockStatement",
             body: [],
@@ -12220,39 +12123,6 @@ test("({ x({ a: { w, x }, b: [y, z] }, ...[a, b, c]){} })", {
               end: {line: 1, column: 48}
             }
           },
-          rest: {
-            type: "ArrayPattern",
-            elements: [
-              {
-                type: "Identifier",
-                name: "a",
-                loc: {
-                  start: {line: 1, column: 37},
-                  end: {line: 1, column: 38}
-                }
-              },
-              {
-                type: "Identifier",
-                name: "b",
-                loc: {
-                  start: {line: 1, column: 40},
-                  end: {line: 1, column: 41}
-                }
-              },
-              {
-                type: "Identifier",
-                name: "c",
-                loc: {
-                  start: {line: 1, column: 43},
-                  end: {line: 1, column: 44}
-                }
-              }
-            ],
-            loc: {
-              start: {line: 1, column: 36},
-              end: {line: 1, column: 45}
-            }
-          },
           generator: false,
           expression: false,
           loc: {
@@ -12296,8 +12166,17 @@ test("(...a) => {}", {
     expression: {
       type: "ArrowFunctionExpression",
       id: null,
-      params: [],
-      defaults: [],
+      params: [{
+        type: "RestElement",
+        argument: {
+          type: "Identifier",
+          name: "a",
+          loc: {
+            start: {line: 1, column: 4},
+            end: {line: 1, column: 5}
+          }
+        }
+      }],
       body: {
         type: "BlockStatement",
         body: [],
@@ -12306,14 +12185,6 @@ test("(...a) => {}", {
           end: {line: 1, column: 12}
         }
       },
-      rest: {
-        type: "Identifier",
-        name: "a",
-        loc: {
-          start: {line: 1, column: 4},
-          end: {line: 1, column: 5}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -12343,15 +12214,27 @@ test("(a, ...b) => {}", {
     expression: {
       type: "ArrowFunctionExpression",
       id: null,
-      params: [{
-        type: "Identifier",
-        name: "a",
-        loc: {
-          start: {line: 1, column: 1},
-          end: {line: 1, column: 2}
+      params: [
+        {
+          type: "Identifier",
+          name: "a",
+          loc: {
+            start: {line: 1, column: 1},
+            end: {line: 1, column: 2}
+          }
+        },
+        {
+          type: "RestElement",
+          argument: {
+            type: "Identifier",
+            name: "b",
+            loc: {
+              start: {line: 1, column: 7},
+              end: {line: 1, column: 8}
+            }
+          }
         }
-      }],
-      defaults: [],
+      ],
       body: {
         type: "BlockStatement",
         body: [],
@@ -12360,14 +12243,6 @@ test("(a, ...b) => {}", {
           end: {line: 1, column: 15}
         }
       },
-      rest: {
-        type: "Identifier",
-        name: "b",
-        loc: {
-          start: {line: 1, column: 7},
-          end: {line: 1, column: 8}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -12431,7 +12306,6 @@ test("({ a }) => {}", {
           end: {line: 1, column: 6}
         }
       }],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [],
@@ -12440,7 +12314,6 @@ test("({ a }) => {}", {
           end: {line: 1, column: 13}
         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -12470,41 +12343,53 @@ test("({ a }, ...b) => {}", {
     expression: {
       type: "ArrowFunctionExpression",
       id: null,
-      params: [{
-        type: "ObjectPattern",
-        properties: [{
-          type: "Property",
-          key: {
-            type: "Identifier",
-            name: "a",
+      params: [
+        {
+          type: "ObjectPattern",
+          properties: [{
+            type: "Property",
+            key: {
+              type: "Identifier",
+              name: "a",
+              loc: {
+                start: {line: 1, column: 3},
+                end: {line: 1, column: 4}
+              }
+            },
+            value: {
+              type: "Identifier",
+              name: "a",
+              loc: {
+                start: {line: 1, column: 3},
+                end: {line: 1, column: 4}
+              }
+            },
+            kind: "init",
+            method: false,
+            shorthand: true,
+            computed: false,
             loc: {
               start: {line: 1, column: 3},
               end: {line: 1, column: 4}
             }
-          },
-          value: {
-            type: "Identifier",
-            name: "a",
-            loc: {
-              start: {line: 1, column: 3},
-              end: {line: 1, column: 4}
-            }
-          },
-          kind: "init",
-          method: false,
-          shorthand: true,
-          computed: false,
+          }],
           loc: {
-            start: {line: 1, column: 3},
-            end: {line: 1, column: 4}
+            start: {line: 1, column: 1},
+            end: {line: 1, column: 6}
+          }
+        },
+        {
+          type: "RestElement",
+          argument: {
+            type: "Identifier",
+            name: "b",
+            loc: {
+              start: {line: 1, column: 11},
+              end: {line: 1, column: 12}
+            }
           }
-        }],
-        loc: {
-          start: {line: 1, column: 1},
-          end: {line: 1, column: 6}
         }
-      }],
-      defaults: [],
+      ],
       body: {
         type: "BlockStatement",
         body: [],
@@ -12513,14 +12398,6 @@ test("({ a }, ...b) => {}", {
           end: {line: 1, column: 19}
         }
       },
-      rest: {
-        type: "Identifier",
-        name: "b",
-        loc: {
-          start: {line: 1, column: 11},
-          end: {line: 1, column: 12}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -12550,8 +12427,34 @@ test("(...[a, b]) => {}", {
     expression: {
       type: "ArrowFunctionExpression",
       id: null,
-      params: [],
-      defaults: [],
+      params: [{
+        type: "RestElement",
+        argument: {
+          type: "ArrayPattern",
+          elements: [
+            {
+              type: "Identifier",
+              name: "a",
+              loc: {
+                start: {line: 1, column: 5},
+                end: {line: 1, column: 6}
+              }
+            },
+            {
+              type: "Identifier",
+              name: "b",
+              loc: {
+                start: {line: 1, column: 8},
+                end: {line: 1, column: 9}
+              }
+            }
+          ],
+          loc: {
+            start: {line: 1, column: 4},
+            end: {line: 1, column: 10}
+          }
+        }
+      }],
       body: {
         type: "BlockStatement",
         body: [],
@@ -12560,31 +12463,6 @@ test("(...[a, b]) => {}", {
           end: {line: 1, column: 17}
         }
       },
-      rest: {
-        type: "ArrayPattern",
-        elements: [
-          {
-            type: "Identifier",
-            name: "a",
-            loc: {
-              start: {line: 1, column: 5},
-              end: {line: 1, column: 6}
-            }
-          },
-          {
-            type: "Identifier",
-            name: "b",
-            loc: {
-              start: {line: 1, column: 8},
-              end: {line: 1, column: 9}
-            }
-          }
-        ],
-        loc: {
-          start: {line: 1, column: 4},
-          end: {line: 1, column: 10}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -12614,15 +12492,34 @@ test("(a, ...[b]) => {}", {
     expression: {
       type: "ArrowFunctionExpression",
       id: null,
-      params: [{
-        type: "Identifier",
-        name: "a",
-        loc: {
-          start: {line: 1, column: 1},
-          end: {line: 1, column: 2}
+      params: [
+        {
+          type: "Identifier",
+          name: "a",
+          loc: {
+            start: {line: 1, column: 1},
+            end: {line: 1, column: 2}
+          }
+        },
+        {
+          type: "RestElement",
+          argument: {
+            type: "ArrayPattern",
+            elements: [{
+              type: "Identifier",
+              name: "b",
+              loc: {
+                start: {line: 1, column: 8},
+                end: {line: 1, column: 9}
+              }
+            }],
+            loc: {
+              start: {line: 1, column: 7},
+              end: {line: 1, column: 10}
+            }
+          }
         }
-      }],
-      defaults: [],
+      ],
       body: {
         type: "BlockStatement",
         body: [],
@@ -12631,21 +12528,6 @@ test("(a, ...[b]) => {}", {
           end: {line: 1, column: 17}
         }
       },
-      rest: {
-        type: "ArrayPattern",
-        elements: [{
-          type: "Identifier",
-          name: "b",
-          loc: {
-            start: {line: 1, column: 8},
-            end: {line: 1, column: 9}
-          }
-        }],
-        loc: {
-          start: {line: 1, column: 7},
-          end: {line: 1, column: 10}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -12675,58 +12557,70 @@ test("({ a: [a, b] }, ...c) => {}", {
     expression: {
       type: "ArrowFunctionExpression",
       id: null,
-      params: [{
-        type: "ObjectPattern",
-        properties: [{
-          type: "Property",
-          key: {
-            type: "Identifier",
-            name: "a",
+      params: [
+        {
+          type: "ObjectPattern",
+          properties: [{
+            type: "Property",
+            key: {
+              type: "Identifier",
+              name: "a",
+              loc: {
+                start: {line: 1, column: 3},
+                end: {line: 1, column: 4}
+              }
+            },
+            value: {
+              type: "ArrayPattern",
+              elements: [
+                {
+                  type: "Identifier",
+                  name: "a",
+                  loc: {
+                    start: {line: 1, column: 7},
+                    end: {line: 1, column: 8}
+                  }
+                },
+                {
+                  type: "Identifier",
+                  name: "b",
+                  loc: {
+                    start: {line: 1, column: 10},
+                    end: {line: 1, column: 11}
+                  }
+                }
+              ],
+              loc: {
+                start: {line: 1, column: 6},
+                end: {line: 1, column: 12}
+              }
+            },
+            kind: "init",
+            method: false,
+            shorthand: false,
+            computed: false,
             loc: {
               start: {line: 1, column: 3},
-              end: {line: 1, column: 4}
-            }
-          },
-          value: {
-            type: "ArrayPattern",
-            elements: [
-              {
-                type: "Identifier",
-                name: "a",
-                loc: {
-                  start: {line: 1, column: 7},
-                  end: {line: 1, column: 8}
-                }
-              },
-              {
-                type: "Identifier",
-                name: "b",
-                loc: {
-                  start: {line: 1, column: 10},
-                  end: {line: 1, column: 11}
-                }
-              }
-            ],
-            loc: {
-              start: {line: 1, column: 6},
               end: {line: 1, column: 12}
             }
-          },
-          kind: "init",
-          method: false,
-          shorthand: false,
-          computed: false,
+          }],
           loc: {
-            start: {line: 1, column: 3},
-            end: {line: 1, column: 12}
+            start: {line: 1, column: 1},
+            end: {line: 1, column: 14}
+          }
+        },
+        {
+          type: "RestElement",
+          argument: {
+            type: "Identifier",
+            name: "c",
+            loc: {
+              start: {line: 1, column: 19},
+              end: {line: 1, column: 20}
+            }
           }
-        }],
-        loc: {
-          start: {line: 1, column: 1},
-          end: {line: 1, column: 14}
         }
-      }],
-      defaults: [],
+      ],
       body: {
         type: "BlockStatement",
         body: [],
@@ -12735,14 +12629,6 @@ test("({ a: [a, b] }, ...c) => {}", {
           end: {line: 1, column: 27}
         }
       },
-      rest: {
-        type: "Identifier",
-        name: "c",
-        loc: {
-          start: {line: 1, column: 19},
-          end: {line: 1, column: 20}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -12860,9 +12746,19 @@ test("({ a: b, c }, [d, e], ...f) => {}", {
             start: {line: 1, column: 14},
             end: {line: 1, column: 20}
           }
+        },
+        {
+          type: "RestElement",
+          argument: {
+            type: "Identifier",
+            name: "f",
+            loc: {
+              start: {line: 1, column: 25},
+              end: {line: 1, column: 26}
+            }
+          }
         }
       ],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [],
@@ -12871,14 +12767,6 @@ test("({ a: b, c }, [d, e], ...f) => {}", {
           end: {line: 1, column: 33}
         }
       },
-      rest: {
-        type: "Identifier",
-        name: "f",
-        loc: {
-          start: {line: 1, column: 25},
-          end: {line: 1, column: 26}
-        }
-      },
       generator: false,
       expression: false,
       loc: {
@@ -13981,7 +13869,6 @@ test("e => yield* 10", {
           end: {line: 1, column: 1}
         }
       }],
-      defaults: [],
       body: {
         type: "BinaryExpression",
         operator: "*",
@@ -14007,7 +13894,6 @@ test("e => yield* 10", {
           end: {line: 1, column: 14}
         }
       },
-      rest: null,
       generator: false,
       expression: true,
       loc: {
@@ -14041,7 +13927,6 @@ test("(function () { yield* 10 })", {
       type: "FunctionExpression",
       id: null,
       params: [],
-      defaults: [],
       body: {
         type: "BlockStatement",
         body: [{
@@ -14081,7 +13966,6 @@ test("(function () { yield* 10 })", {
           end: {line: 1, column: 26}
         }
       },
-      rest: null,
       generator: false,
       expression: false,
       loc: {
@@ -14317,19 +14201,18 @@ test('function normal(x, y = 10) {}', {
         name: "x"
       },
       {
-        type: "Identifier",
-        name: "y"
+        type: "AssignmentPattern",
+        left: {
+          type: "Identifier",
+          name: "y"
+        },
+        right: {
+          type: "Literal",
+          value: 10,
+          raw: "10"
+        }
       }
     ],
-    defaults: [
-      null,
-      {
-        type: "Literal",
-        value: 10,
-        raw: "10"
-      }
-    ],
-    rest: null,
     generator: false,
     body: {
       type: "BlockStatement",
@@ -14714,8 +14597,6 @@ test("class A { static() {} }", {
           range: [16, 21],
           id: null,
           params: [],
-          defaults: [],
-          rest: null,
           generator: false,
           body: {
             type: "BlockStatement",
@@ -14764,8 +14645,6 @@ test("class A { *static() {} }", {
           range: [17, 22],
           id: null,
           params: [],
-          defaults: [],
-          rest: null,
           generator: true,
           body: {
             type: "BlockStatement",
diff --git a/test/tests.js b/test/tests.js
index d3beafc5f9..dfbfda0438 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -23788,21 +23788,23 @@ test("function hello(...rest) { }", {
           }
         }
       },
-      params: [],
-      rest: {
-        type: "Identifier",
-        name: "rest",
-        loc: {
-          start: {
-            line: 1,
-            column: 18
-          },
-          end: {
-            line: 1,
-            column: 22
+      params: [{
+        type: "RestElement",
+        argument: {
+          type: "Identifier",
+          name: "rest",
+          loc: {
+            start: {
+              line: 1,
+              column: 18
+            },
+            end: {
+              line: 1,
+              column: 22
+            }
           }
         }
-      },
+      }],
       body: {
         type: "BlockStatement",
         body: [],
@@ -23877,22 +23879,25 @@ test("function hello(a, ...rest) { }", {
               column: 16
             }
           }
-        }
-      ],
-      rest: {
-        type: "Identifier",
-        name: "rest",
-        loc: {
-          start: {
-            line: 1,
-            column: 21
-          },
-          end: {
-            line: 1,
-            column: 25
+        },
+        {
+          type: "RestElement",
+          argument: {
+            type: "Identifier",
+            name: "rest",
+            loc: {
+              start: {
+                line: 1,
+                column: 21
+              },
+              end: {
+                line: 1,
+                column: 25
+              }
+            }
           }
         }
-      },
+      ],
       body: {
         type: "BlockStatement",
         body: [],
@@ -24089,21 +24094,23 @@ test("var hi = function (...r) { sayHi() };", {
           init: {
             type: "FunctionExpression",
             id: null,
-            params: [],
-            rest: {
-              type: "Identifier",
-              name: "r",
-              loc: {
-                start: {
-                  line: 1,
-                  column: 22
-                },
-                end: {
-                  line: 1,
-                  column: 23
+            params: [{
+              type: "RestElement",
+              argument: {
+                type: "Identifier",
+                name: "r",
+                loc: {
+                  start: {
+                    line: 1,
+                    column: 22
+                  },
+                  end: {
+                    line: 1,
+                    column: 23
+                  }
                 }
               }
-            },
+            }],
             body: {
               type: "BlockStatement",
               body: [

From 2e9180f0417122228e4f84426dba86752ccaa1e9 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 15:33:28 +0200
Subject: [PATCH 08/14] Add ES6 patterns to util/walk.js

---
 util/walk.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/util/walk.js b/util/walk.js
index da7ca9f7e1..5a09df7ddc 100644
--- a/util/walk.js
+++ b/util/walk.js
@@ -200,7 +200,7 @@
   base.ReturnStatement = base.YieldExpression = function(node, st, c) {
     if (node.argument) c(node.argument, st, "Expression");
   };
-  base.ThrowStatement = base.SpreadElement = function(node, st, c) {
+  base.ThrowStatement = base.SpreadElement = base.RestElement = function(node, st, c) {
     c(node.argument, st, "Expression");
   };
   base.TryStatement = function(node, st, c) {
@@ -249,13 +249,13 @@
 
   base.Expression = skipThrough;
   base.ThisExpression = ignore;
-  base.ArrayExpression = function(node, st, c) {
+  base.ArrayExpression = base.ArrayPattern =  function(node, st, c) {
     for (var i = 0; i < node.elements.length; ++i) {
       var elt = node.elements[i];
       if (elt) c(elt, st, "Expression");
     }
   };
-  base.ObjectExpression = function(node, st, c) {
+  base.ObjectExpression = base.ObjectPattern = function(node, st, c) {
     for (var i = 0; i < node.properties.length; ++i)
       c(node.properties[i], st);
   };
@@ -267,7 +267,7 @@
   base.UnaryExpression = base.UpdateExpression = function(node, st, c) {
     c(node.argument, st, "Expression");
   };
-  base.BinaryExpression = base.AssignmentExpression = base.LogicalExpression = function(node, st, c) {
+  base.BinaryExpression = base.AssignmentExpression = base.AssignmentPattern = base.LogicalExpression = function(node, st, c) {
     c(node.left, st, "Expression");
     c(node.right, st, "Expression");
   };

From 08b34933d7608470bbbb62a291fb515e4759e197 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 15:39:49 +0200
Subject: [PATCH 09/14] Added acorn_csp to .gitignore and fixed generation
 under Windows.

---
 .gitignore   | 1 +
 package.json | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.gitignore b/.gitignore
index 7a9d2aa37c..088a673331 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 /node_modules
 /.tern-port
+/acorn_csp.js
diff --git a/package.json b/package.json
index e8d244ea07..63412ab22d 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,7 @@
                   "url": "http://marijnhaverbeke.nl/acorn/LICENSE"}],
     "scripts": {
       "test": "node test/run.js",
-      "prepublish": "bin/without_eval > acorn_csp.js"
+      "prepublish": "node bin/without_eval > acorn_csp.js"
     },
     "bin": {"acorn": "./bin/acorn"},
     "devDependencies": {"regenerate": "~0.6.2",

From 41ad304955d6770f2f226edfdb463b74699628c5 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 21:36:16 +0200
Subject: [PATCH 10/14] Introduce helpers for contextual keywords.

---
 acorn.js       | 48 ++++++++++++++++++++++++++----------------------
 acorn_loose.js | 42 +++++++++++++++++-------------------------
 2 files changed, 43 insertions(+), 47 deletions(-)

diff --git a/acorn.js b/acorn.js
index 6cf6a60443..35015ad1aa 100644
--- a/acorn.js
+++ b/acorn.js
@@ -1414,6 +1414,24 @@
     }
   }
 
+  // Tests whether parsed token is a contextual keyword.
+
+  function isContextual(name) {
+    return tokType === _name && tokVal === name;
+  }
+
+  // Consumes contextual keyword if possible.
+
+  function eatContextual(name) {
+    return tokVal === name && eat(_name);
+  }
+
+  // Asserts that following token is given contextual keyword.
+
+  function expectContextual(name) {
+    if (!eatContextual(name)) unexpected();
+  }
+
   // Test whether a semicolon can be inserted at the current position.
 
   function canInsertSemicolon() {
@@ -1814,13 +1832,13 @@
       next();
       parseVar(init, true, varKind);
       finishNode(init, "VariableDeclaration");
-      if ((tokType === _in || (options.ecmaVersion >= 6 && tokType === _name && tokVal === "of")) && init.declarations.length === 1 &&
+      if ((tokType === _in || (options.ecmaVersion >= 6 && isContextual("of"))) && init.declarations.length === 1 &&
           !(isLet && init.declarations[0].init))
         return parseForIn(node, init);
       return parseFor(node, init);
     }
     var init = parseExpression(false, true);
-    if (tokType === _in || (options.ecmaVersion >= 6 && tokType === _name && tokVal === "of")) {
+    if (tokType === _in || (options.ecmaVersion >= 6 && isContextual("of"))) {
       checkLVal(init);
       return parseForIn(node, init);
     }
@@ -2631,8 +2649,7 @@
       node.declaration = null;
       node['default'] = false;
       node.specifiers = parseExportSpecifiers();
-      if (tokType === _name && tokVal === "from") {
-        next();
+      if (eatContextual("from")) {
         node.source = tokType === _string ? parseExprAtom() : unexpected();
       } else {
         if (isBatch) unexpected();
@@ -2663,12 +2680,7 @@
 
         var node = startNode();
         node.id = parseIdent(tokType === _default);
-        if (tokType === _name && tokVal === "as") {
-          next();
-          node.name = parseIdent(true);
-        } else {
-          node.name = null;
-        }
+        node.name = eatContextual("as") ? parseIdent(true) : null;
         nodes.push(finishNode(node, "ExportSpecifier"));
       }
     }
@@ -2686,8 +2698,7 @@
       node.kind = "";
     } else {
       node.specifiers = parseImportSpecifiers();
-      if (tokType !== _name || tokVal !== "from") unexpected();
-      next();
+      expectContextual("from");
       node.source = tokType === _string ? parseExprAtom() : unexpected();
     }
     semicolon();
@@ -2711,8 +2722,7 @@
     if (tokType === _star) {
       var node = startNode();
       next();
-      if (tokType !== _name || tokVal !== "as") unexpected();
-      next();
+      expectContextual("as");
       node.name = parseIdent();
       checkLVal(node.name, true);
       nodes.push(finishNode(node, "ImportBatchSpecifier"));
@@ -2727,12 +2737,7 @@
 
       var node = startNode();
       node.id = parseIdent(true);
-      if (tokType === _name && tokVal === "as") {
-        next();
-        node.name = parseIdent();
-      } else {
-        node.name = null;
-      }
+      node.name = eatContextual("as") ? parseIdent() : null;
       checkLVal(node.name || node.id, true);
       node['default'] = false;
       nodes.push(finishNode(node, "ImportSpecifier"));
@@ -2765,8 +2770,7 @@
       expect(_parenL);
       block.left = parseAssignableAtom();
       checkLVal(block.left, true);
-      if (tokType !== _name || tokVal !== "of") unexpected();
-      next();
+      expectContextual("of");
       block.right = parseExpression();
       expect(_parenR);
       node.blocks.push(finishNode(block, "ComprehensionBlock"));
diff --git a/acorn_loose.js b/acorn_loose.js
index e1ee14fc3c..44b0870cd9 100644
--- a/acorn_loose.js
+++ b/acorn_loose.js
@@ -271,9 +271,18 @@
     }
   }
 
+  function isContextual(name) {
+    return token.type === tt.name && token.value === name;
+  }
+
+  function eatContextual(name) {
+    return token.value === name && eat(tt.name);
+  }
+
   function canInsertSemicolon() {
     return (token.type === tt.eof || token.type === tt.braceR || newline.test(input.slice(lastEnd, token.start)));
   }
+
   function semicolon() {
     return eat(tt.semi);
   }
@@ -352,13 +361,13 @@
       if (token.type === tt.semi) return parseFor(node, null);
       if (token.type === tt._var || token.type === tt._let) {
         var init = parseVar(true);
-        if (init.declarations.length === 1 && (token.type === tt._in || token.type === tt.name && token.value === "of")) {
+        if (init.declarations.length === 1 && (token.type === tt._in || isContextual("of"))) {
           return parseForIn(node, init);
         }
         return parseFor(node, init);
       }
       var init = parseExpression(false, true);
-      if (token.type === tt._in || token.type === tt.name && token.value === "of") {
+      if (token.type === tt._in || isContextual("of")) {
         return parseForIn(node, checkLVal(init));
       }
       return parseFor(node, init);
@@ -1080,10 +1089,7 @@
     if (token.type === tt.star) {
       var elt = startNode();
       next();
-      if (token.type === tt.name && token.value === "as") {
-        next();
-        elt.name = parseIdent();
-      }
+      if (eatContextual("as")) elt.name = parseIdent();
       elts.push(finishNode(elt, prefix + "BatchSpecifier"));
     } else {
       var indent = curIndent, line = curLineStart, continuedLine = nextLineStart;
@@ -1092,22 +1098,13 @@
       if (curLineStart > continuedLine) continuedLine = curLineStart;
       while (!closes(tt.braceR, indent + (curLineStart <= continuedLine ? 1 : 0), line)) {
         var elt = startNode();
-        if (token.type === tt.star) {
-          next();
-          if (token.type === tt.name && token.value === "as") {
-            next();
-            elt.name = parseIdent();
-          }
+        if (eat(tt.star)) {
+          if (eatContextual("as")) elt.name = parseIdent();
           finishNode(elt, prefix + "BatchSpecifier");
         } else {
-          if (token.type === tt.name && token.value === "from") break;
+          if (isContextual("from")) break;
           elt.id = parseIdent();
-          if (token.type === tt.name && token.value === "as") {
-            next();
-            elt.name = parseIdent();
-          } else {
-            elt.name = null;
-          }
+          elt.name = eatContextual("as") ? parseIdent() : null;
           finishNode(elt, prefix + "Specifier");
         }
         elts.push(elt);
@@ -1116,12 +1113,7 @@
       eat(tt.braceR);
       popCx();
     }
-    if (token.type === tt.name && token.value === "from") {
-      next();
-      node.source = parseExprAtom();
-    } else {
-      node.source = null;
-    }
+    node.source = eatContextual("from") ? parseExprAtom() : null;
   }
 
   function parseExprList(close, allowEmpty) {

From f0569147e6b34b94c60f0bdf2edcd8d092012a5d Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 21:48:33 +0200
Subject: [PATCH 11/14] Avoid extra call and arg in parseExpression for
 single-expression case.

---
 acorn.js       | 18 +++++++++---------
 acorn_loose.js | 24 ++++++++++++------------
 2 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/acorn.js b/acorn.js
index 35015ad1aa..d7fc369fed 100644
--- a/acorn.js
+++ b/acorn.js
@@ -1837,7 +1837,7 @@
         return parseForIn(node, init);
       return parseFor(node, init);
     }
-    var init = parseExpression(false, true);
+    var init = parseExpression(true);
     if (tokType === _in || (options.ecmaVersion >= 6 && isContextual("of"))) {
       checkLVal(init);
       return parseForIn(node, init);
@@ -2054,7 +2054,7 @@
       var decl = startNode();
       decl.id = parseAssignableAtom();
       checkLVal(decl.id, true);
-      decl.init = eat(_eq) ? parseExpression(true, noIn) : (kind === _const.keyword ? unexpected() : null);
+      decl.init = eat(_eq) ? parseMaybeAssign(noIn) : (kind === _const.keyword ? unexpected() : null);
       node.declarations.push(finishNode(decl, "VariableDeclarator"));
       if (!eat(_comma)) break;
     }
@@ -2073,10 +2073,10 @@
   // sequences (in argument lists, array literals, or object literals)
   // or the `in` operator (in for loops initalization expressions).
 
-  function parseExpression(noComma, noIn) {
+  function parseExpression(noIn) {
     var start = storeCurrentPos();
     var expr = parseMaybeAssign(noIn);
-    if (!noComma && tokType === _comma) {
+    if (tokType === _comma) {
       var node = startNodeAt(start);
       node.expressions = [expr];
       while (eat(_comma)) node.expressions.push(parseMaybeAssign(noIn));
@@ -2111,9 +2111,9 @@
     if (eat(_question)) {
       var node = startNodeAt(start);
       node.test = expr;
-      node.consequent = parseExpression(true);
+      node.consequent = parseMaybeAssign();
       expect(_colon);
-      node.alternate = parseExpression(true, noIn);
+      node.alternate = parseMaybeAssign(noIn);
       return finishNode(node, "ConditionalExpression");
     }
     return expr;
@@ -2514,7 +2514,7 @@
     var isExpression = allowExpression && tokType !== _braceL;
 
     if (isExpression) {
-      node.body = parseExpression(true);
+      node.body = parseMaybeAssign();
       node.expression = true;
     } else {
       // Start a new scope with regard to labels and the `inFunction`
@@ -2637,7 +2637,7 @@
     } else
     // export default ...;
     if (eat(_default)) {
-      node.declaration = parseExpression(true);
+      node.declaration = parseMaybeAssign();
       node['default'] = true;
       node.specifiers = null;
       node.source = null;
@@ -2755,7 +2755,7 @@
       node.argument = null;
     } else {
       node.delegate = eat(_star);
-      node.argument = parseExpression(true);
+      node.argument = parseMaybeAssign();
     }
     return finishNode(node, "YieldExpression");
   }
diff --git a/acorn_loose.js b/acorn_loose.js
index 44b0870cd9..297589a498 100644
--- a/acorn_loose.js
+++ b/acorn_loose.js
@@ -366,7 +366,7 @@
         }
         return parseFor(node, init);
       }
-      var init = parseExpression(false, true);
+      var init = parseExpression(true);
       if (token.type === tt._in || isContextual("of")) {
         return parseForIn(node, checkLVal(init));
       }
@@ -539,7 +539,7 @@
     do {
       var decl = startNode();
       decl.id = options.ecmaVersion >= 6 ? toAssignable(parseExprAtom()) : parseIdent();
-      decl.init = eat(tt.eq) ? parseExpression(true, noIn) : null;
+      decl.init = eat(tt.eq) ? parseMaybeAssign(noIn) : null;
       node.declarations.push(finishNode(decl, "VariableDeclarator"));
     } while (eat(tt.comma));
     if (!node.declarations.length) {
@@ -551,10 +551,10 @@
     return finishNode(node, "VariableDeclaration");
   }
 
-  function parseExpression(noComma, noIn) {
+  function parseExpression(noIn) {
     var start = storeCurrentPos();
     var expr = parseMaybeAssign(noIn);
-    if (!noComma && token.type === tt.comma) {
+    if (token.type === tt.comma) {
       var node = startNodeAt(start);
       node.expressions = [expr];
       while (eat(tt.comma)) node.expressions.push(parseMaybeAssign(noIn));
@@ -592,8 +592,8 @@
     if (eat(tt.question)) {
       var node = startNodeAt(start);
       node.test = expr;
-      node.consequent = parseExpression(true);
-      node.alternate = expect(tt.colon) ? parseExpression(true, noIn) : dummyIdent();
+      node.consequent = parseMaybeAssign();
+      node.alternate = expect(tt.colon) ? parseMaybeAssign(noIn) : dummyIdent();
       return finishNode(node, "ConditionalExpression");
     }
     return expr;
@@ -783,7 +783,7 @@
         node.argument = null;
       } else {
         node.delegate = eat(tt.star);
-        node.argument = parseExpression(true);
+        node.argument = parseMaybeAssign();
       }
       return finishNode(node, "YieldExpression");
 
@@ -871,7 +871,7 @@
         isGenerator = eat(tt.star);
       }
       parsePropertyName(prop);
-      if (isDummy(prop.key)) { if (isDummy(parseExpression(true))) next(); eat(tt.comma); continue; }
+      if (isDummy(prop.key)) { if (isDummy(parseMaybeAssign())) next(); eat(tt.comma); continue; }
       if (isClass) {
         if (prop.key.type === "Identifier" && !prop.computed && prop.key.name === "static" &&
             (token.type != tt.parenL && token.type != tt.braceL)) {
@@ -884,7 +884,7 @@
       }
       if (!isClass && eat(tt.colon)) {
         prop.kind = "init";
-        prop.value = parseExpression(true);
+        prop.value = parseMaybeAssign();
       } else if (options.ecmaVersion >= 6 && (token.type === tt.parenL || token.type === tt.braceL)) {
         if (isClass) {
           prop.kind = "";
@@ -1029,7 +1029,7 @@
     node.params = parseFunctionParams();
     node.generator = isGenerator || false;
     node.expression = options.ecmaVersion >= 6 && token.type !== tt.braceL;
-    node.body = node.expression ? parseExpression(true) : parseBlock();
+    node.body = node.expression ? parseMaybeAssign() : parseBlock();
     return finishNode(node, "FunctionExpression");
   }
 
@@ -1037,7 +1037,7 @@
     initFunction(node);
     node.params = toAssignableList(params);
     node.expression = token.type !== tt.braceL;
-    node.body = node.expression ? parseExpression(true) : parseBlock();
+    node.body = node.expression ? parseMaybeAssign() : parseBlock();
     return finishNode(node, "ArrowFunctionExpression");
   }
 
@@ -1124,7 +1124,7 @@
         elts.push(allowEmpty ? null : dummyIdent());
         continue;
       }
-      var elt = parseExpression(true);
+      var elt = parseMaybeAssign();
       if (isDummy(elt)) {
         if (closes(close, indent, line)) break;
         next();

From 65d09eac6eeeec5dda2a03db715e881892a9675d Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Fri, 23 Jan 2015 23:41:03 +0200
Subject: [PATCH 12/14] Implement shorthand property assignment in ambiguous
 contexts.

Issue #181.
---
 acorn.js              | 138 ++++++++++++++--------
 test/tests-harmony.js | 265 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 348 insertions(+), 55 deletions(-)

diff --git a/acorn.js b/acorn.js
index d7fc369fed..01f7037033 100644
--- a/acorn.js
+++ b/acorn.js
@@ -1468,7 +1468,7 @@
   // Convert existing expression atom to assignable pattern
   // if possible.
 
-  function toAssignable(node, allowSpread, checkType) {
+  function toAssignable(node) {
     if (options.ecmaVersion >= 6 && node) {
       switch (node.type) {
         case "Identifier":
@@ -1476,43 +1476,32 @@
         case "ObjectPattern":
         case "ArrayPattern":
         case "AssignmentPattern":
-        case "RestElement":
           break;
 
         case "ObjectExpression":
           node.type = "ObjectPattern";
           for (var i = 0; i < node.properties.length; i++) {
             var prop = node.properties[i];
-            if (prop.kind !== "init") unexpected(prop.key.start);
-            toAssignable(prop.value, false, checkType);
+            if (prop.kind !== "init") raise(prop.key.start, "Object pattern can't contain getter or setter");
+            toAssignable(prop.value);
           }
           break;
 
         case "ArrayExpression":
           node.type = "ArrayPattern";
-          toAssignableList(node.elements, checkType);
-          break;
-
-        case "SpreadElement":
-          if (allowSpread) {
-            node.type = "RestElement";
-            toAssignable(node.argument, false, checkType);
-            checkSpreadAssign(node.argument);
-          } else {
-            unexpected(node.start);
-          }
+          toAssignableList(node.elements);
           break;
 
         case "AssignmentExpression":
           if (node.operator === "=") {
             node.type = "AssignmentPattern";
           } else {
-            unexpected(node.left.end);
+            raise(node.left.end, "Only '=' operator can be used for specifying default value.");
           }
           break;
 
         default:
-          if (checkType) unexpected(node.start);
+          raise(node.start, "Assigning to rvalue");
       }
     }
     return node;
@@ -1520,19 +1509,33 @@
 
   // Convert list of expression atoms to binding list.
 
-  function toAssignableList(exprList, checkType) {
-    for (var i = 0; i < exprList.length; i++) {
-      toAssignable(exprList[i], i === exprList.length - 1, checkType);
+  function toAssignableList(exprList) {
+    if (exprList.length) {
+      for (var i = 0; i < exprList.length - 1; i++) {
+        toAssignable(exprList[i]);
+      }
+      var last = exprList[exprList.length - 1];
+      switch (last.type) {
+        case "RestElement":
+          break;
+        case "SpreadElement":
+          last.type = "RestElement";
+          toAssignable(last.argument);
+          checkSpreadAssign(last.argument);
+          break;
+        default:
+          toAssignable(last);
+      }
     }
     return exprList;
   }
 
   // Parses spread element.
 
-  function parseSpread() {
+  function parseSpread(refShorthandDefaultPos) {
     var node = startNode();
     next();
-    node.argument = parseMaybeAssign();
+    node.argument = parseMaybeAssign(refShorthandDefaultPos);
     return finishNode(node, "SpreadElement");
   }
 
@@ -1837,10 +1840,14 @@
         return parseForIn(node, init);
       return parseFor(node, init);
     }
-    var init = parseExpression(true);
+    var refShorthandDefaultPos = {start: 0};
+    var init = parseExpression(true, refShorthandDefaultPos);
     if (tokType === _in || (options.ecmaVersion >= 6 && isContextual("of"))) {
+      toAssignable(init);
       checkLVal(init);
       return parseForIn(node, init);
+    } else if (refShorthandDefaultPos.start) {
+      unexpected(refShorthandDefaultPos.start);
     }
     return parseFor(node, init);
   }
@@ -2069,17 +2076,20 @@
   // and, *if* the syntactic construct they handle is present, wrap
   // the AST node that the inner parser gave them in another node.
 
-  // Parse a full expression. The arguments are used to forbid comma
-  // sequences (in argument lists, array literals, or object literals)
-  // or the `in` operator (in for loops initalization expressions).
+  // Parse a full expression. The optional arguments are used to
+  // forbid the `in` operator (in for loops initalization expressions)
+  // and provide reference for storing '=' operator inside shorthand
+  // property assignment in contexts where both object expression
+  // and object pattern might appear (so it's possible to raise
+  // delayed syntax error at correct position).
 
-  function parseExpression(noIn) {
+  function parseExpression(noIn, refShorthandDefaultPos) {
     var start = storeCurrentPos();
-    var expr = parseMaybeAssign(noIn);
+    var expr = parseMaybeAssign(noIn, refShorthandDefaultPos);
     if (tokType === _comma) {
       var node = startNodeAt(start);
       node.expressions = [expr];
-      while (eat(_comma)) node.expressions.push(parseMaybeAssign(noIn));
+      while (eat(_comma)) node.expressions.push(parseMaybeAssign(noIn, refShorthandDefaultPos));
       return finishNode(node, "SequenceExpression");
     }
     return expr;
@@ -2088,26 +2098,37 @@
   // Parse an assignment expression. This includes applications of
   // operators like `+=`.
 
-  function parseMaybeAssign(noIn) {
+  function parseMaybeAssign(noIn, refShorthandDefaultPos) {
+    var failOnShorthandAssign;
+    if (!refShorthandDefaultPos) {
+      refShorthandDefaultPos = {start: 0};
+      failOnShorthandAssign = true;
+    } else {
+      failOnShorthandAssign = false;
+    }
     var start = storeCurrentPos();
-    var left = parseMaybeConditional(noIn);
+    var left = parseMaybeConditional(noIn, refShorthandDefaultPos);
     if (tokType.isAssign) {
       var node = startNodeAt(start);
       node.operator = tokVal;
       node.left = tokType === _eq ? toAssignable(left) : left;
+      refShorthandDefaultPos.start = 0; // reset because shorthand default was used correctly
       checkLVal(left);
       next();
       node.right = parseMaybeAssign(noIn);
       return finishNode(node, "AssignmentExpression");
+    } else if (failOnShorthandAssign && refShorthandDefaultPos.start) {
+      unexpected(refShorthandDefaultPos.start);
     }
     return left;
   }
 
   // Parse a ternary conditional (`?:`) operator.
 
-  function parseMaybeConditional(noIn) {
+  function parseMaybeConditional(noIn, refShorthandDefaultPos) {
     var start = storeCurrentPos();
-    var expr = parseExprOps(noIn);
+    var expr = parseExprOps(noIn, refShorthandDefaultPos);
+    if (refShorthandDefaultPos && refShorthandDefaultPos.start) return expr;
     if (eat(_question)) {
       var node = startNodeAt(start);
       node.test = expr;
@@ -2121,9 +2142,11 @@
 
   // Start the precedence parser.
 
-  function parseExprOps(noIn) {
+  function parseExprOps(noIn, refShorthandDefaultPos) {
     var start = storeCurrentPos();
-    return parseExprOp(parseMaybeUnary(), start, -1, noIn);
+    var expr = parseMaybeUnary(refShorthandDefaultPos);
+    if (refShorthandDefaultPos && refShorthandDefaultPos.start) return expr;
+    return parseExprOp(expr, start, -1, noIn);
   }
 
   // Parse binary operators with the operator precedence parsing
@@ -2152,13 +2175,14 @@
 
   // Parse unary operators, both prefix and postfix.
 
-  function parseMaybeUnary() {
+  function parseMaybeUnary(refShorthandDefaultPos) {
     if (tokType.prefix) {
       var node = startNode(), update = tokType.isUpdate;
       node.operator = tokVal;
       node.prefix = true;
       next();
       node.argument = parseMaybeUnary();
+      if (refShorthandDefaultPos && refShorthandDefaultPos.start) unexpected(refShorthandDefaultPos.start);
       if (update) checkLVal(node.argument);
       else if (strict && node.operator === "delete" &&
                node.argument.type === "Identifier")
@@ -2166,7 +2190,8 @@
       return finishNode(node, update ? "UpdateExpression" : "UnaryExpression");
     }
     var start = storeCurrentPos();
-    var expr = parseExprSubscripts();
+    var expr = parseExprSubscripts(refShorthandDefaultPos);
+    if (refShorthandDefaultPos && refShorthandDefaultPos.start) return expr;
     while (tokType.postfix && !canInsertSemicolon()) {
       var node = startNodeAt(start);
       node.operator = tokVal;
@@ -2181,9 +2206,11 @@
 
   // Parse call, dot, and `[]`-subscript expressions.
 
-  function parseExprSubscripts() {
+  function parseExprSubscripts(refShorthandDefaultPos) {
     var start = storeCurrentPos();
-    return parseSubscripts(parseExprAtom(), start);
+    var expr = parseExprAtom(refShorthandDefaultPos);
+    if (refShorthandDefaultPos && refShorthandDefaultPos.start) return expr;
+    return parseSubscripts(expr, start);
   }
 
   function parseSubscripts(base, start, noCalls) {
@@ -2218,7 +2245,7 @@
   // `new`, or an expression wrapped in punctuation like `()`, `[]`,
   // or `{}`.
 
-  function parseExprAtom() {
+  function parseExprAtom(refShorthandDefaultPos) {
     switch (tokType) {
     case _this:
       var node = startNode();
@@ -2268,11 +2295,11 @@
       if (options.ecmaVersion >= 7 && tokType === _for) {
         return parseComprehension(node, false);
       }
-      node.elements = parseExprList(_bracketR, true, true);
+      node.elements = parseExprList(_bracketR, true, true, refShorthandDefaultPos);
       return finishNode(node, "ArrayExpression");
 
     case _braceL:
-      return parseObj();
+      return parseObj(false, refShorthandDefaultPos);
 
     case _function:
       var node = startNode();
@@ -2302,7 +2329,8 @@
         return parseComprehension(startNodeAt(start), true);
       }
 
-      var innerStart = storeCurrentPos(), exprList = [], first = true, spreadStart, innerParenStart;
+      var innerStart = storeCurrentPos(), exprList = [], first = true;
+      var refShorthandDefaultPos = {start: 0}, spreadStart, innerParenStart;
       while (tokType !== _parenR) {
         first ? first = false : expect(_comma);
         if (tokType === _ellipsis) {
@@ -2313,7 +2341,7 @@
           if (tokType === _parenL && !innerParenStart) {
             innerParenStart = tokStart;
           }
-          exprList.push(parseMaybeAssign());
+          exprList.push(parseMaybeAssign(false, refShorthandDefaultPos));
         }
       }
       var innerEnd = storeCurrentPos();
@@ -2326,6 +2354,7 @@
 
       if (!exprList.length) unexpected(lastStart);
       if (spreadStart) unexpected(spreadStart);
+      if (refShorthandDefaultPos.start) unexpected(refShorthandDefaultPos.start);
 
       if (exprList.length > 1) {
         val = startNodeAt(innerStart);
@@ -2392,7 +2421,7 @@
 
   // Parse an object literal or binding pattern.
 
-  function parseObj(isPattern) {
+  function parseObj(isPattern, refShorthandDefaultPos) {
     var node = startNode(), first = true, propHash = {};
     node.properties = [];
     next();
@@ -2414,7 +2443,7 @@
       }
       parsePropertyName(prop);
       if (eat(_colon)) {
-        prop.value = isPattern ? parseMaybeDefault(start) : parseMaybeAssign();
+        prop.value = isPattern ? parseMaybeDefault(start) : parseMaybeAssign(false, refShorthandDefaultPos);
         prop.kind = "init";
       } else if (options.ecmaVersion >= 6 && tokType === _parenL) {
         if (isPattern) unexpected();
@@ -2430,7 +2459,15 @@
         prop.value = parseMethod(false);
       } else if (options.ecmaVersion >= 6 && !prop.computed && prop.key.type === "Identifier") {
         prop.kind = "init";
-        prop.value = isPattern ? parseMaybeDefault(start, prop.key) : prop.key;
+        if (isPattern) {
+          prop.value = parseMaybeDefault(start, prop.key);
+        } else if (tokType === _eq && refShorthandDefaultPos) {
+          if (!refShorthandDefaultPos.start)
+            refShorthandDefaultPos.start = tokStart;
+          prop.value = parseMaybeDefault(start, prop.key);
+        } else {
+          prop.value = prop.key;
+        }
         prop.shorthand = true;
       } else unexpected();
 
@@ -2583,7 +2620,7 @@
   // nothing in between them to be parsed as `null` (which is needed
   // for array literals).
 
-  function parseExprList(close, allowTrailingComma, allowEmpty) {
+  function parseExprList(close, allowTrailingComma, allowEmpty, refShorthandDefaultPos) {
     var elts = [], first = true;
     while (!eat(close)) {
       if (!first) {
@@ -2594,7 +2631,10 @@
       if (allowEmpty && tokType === _comma) {
         elts.push(null);
       } else {
-        elts.push(tokType === _ellipsis ? parseSpread() : parseMaybeAssign());
+        if (tokType === _ellipsis)
+          elts.push(parseSpread(refShorthandDefaultPos));
+        else
+          elts.push(parseMaybeAssign(false, refShorthandDefaultPos));
       }
     }
     return elts;
diff --git a/test/tests-harmony.js b/test/tests-harmony.js
index 9fc9dec59c..641f18657f 100644
--- a/test/tests-harmony.js
+++ b/test/tests-harmony.js
@@ -13745,7 +13745,7 @@ testFail("[2] = 42", "Assigning to rvalue (1:1)", {ecmaVersion: 6});
 
 testFail("({ obj:20 }) = 42", "Assigning to rvalue (1:7)", {ecmaVersion: 6});
 
-testFail("( { get x() {} } ) = 0", "Unexpected token (1:8)", {ecmaVersion: 6});
+testFail("( { get x() {} } ) = 0", "Object pattern can't contain getter or setter (1:8)", {ecmaVersion: 6});
 
 testFail("x \n is y", "Unexpected token (2:4)", {ecmaVersion: 6});
 
@@ -13801,9 +13801,9 @@ testFail("\"use strict\"; (a) => 00", "Invalid number (1:21)", {ecmaVersion: 6})
 
 testFail("() <= 42", "Unexpected token (1:1)", {ecmaVersion: 6});
 
-testFail("(10) => 00", "Unexpected token (1:1)", {ecmaVersion: 6});
+testFail("(10) => 00", "Assigning to rvalue (1:1)", {ecmaVersion: 6});
 
-testFail("(10, 20) => 00", "Unexpected token (1:1)", {ecmaVersion: 6});
+testFail("(10, 20) => 00", "Assigning to rvalue (1:1)", {ecmaVersion: 6});
 
 testFail("yield v", "Unexpected token (1:6)", {ecmaVersion: 6});
 
@@ -14037,7 +14037,7 @@ testFail("\"use strict\"; function x(a, ...[a]){}", "Argument name clash in stri
 
 testFail("(...a, b) => {}", "Unexpected token (1:5)", {ecmaVersion: 6});
 
-testFail("([ 5 ]) => {}", "Unexpected token (1:3)", {ecmaVersion: 6});
+testFail("([ 5 ]) => {}", "Assigning to rvalue (1:3)", {ecmaVersion: 6});
 
 testFail("({ 5 }) => {}", "Unexpected token (1:5)", {ecmaVersion: 6});
 
@@ -14045,7 +14045,7 @@ testFail("(...[ 5 ]) => {}", "Unexpected token (1:6)", {ecmaVersion: 6});
 
 testFail("[...{ a }] = b", "Unexpected token (1:4)", {ecmaVersion: 6});
 
-testFail("[...a, b] = c", "Unexpected token (1:1)", {ecmaVersion: 6});
+testFail("[...a, b] = c", "Assigning to rvalue (1:1)", {ecmaVersion: 6});
 
 testFail("({ t(eval) { \"use strict\"; } });", "Defining 'eval' in strict mode (1:5)", {ecmaVersion: 6});
 
@@ -14120,7 +14120,7 @@ testFail("\"use strict\"; (eval) => 42", "Defining 'eval' in strict mode (1:15)"
 
 testFail("(eval) => { \"use strict\"; 42 }", "Defining 'eval' in strict mode (1:1)", {ecmaVersion: 6});
 
-testFail("({ get test() { } }) => 42", "Unexpected token (1:7)", {ecmaVersion: 6});
+testFail("({ get test() { } }) => 42", "Object pattern can't contain getter or setter (1:7)", {ecmaVersion: 6});
 
 /* Regression tests */
 
@@ -14509,6 +14509,259 @@ test("var [localVar = defaultValue] = obj", {
   loose: false
 });
 
+test("({x = 0} = obj)", {
+  type: "Program",
+  range: [0, 15],
+  body: [{
+    type: "ExpressionStatement",
+    range: [0, 15],
+    expression: {
+      type: "AssignmentExpression",
+      range: [1, 14],
+      operator: "=",
+      left: {
+        type: "ObjectPattern",
+        range: [1, 8],
+        properties: [{
+          type: "Property",
+          range: [2, 7],
+          method: false,
+          shorthand: true,
+          computed: false,
+          key: {
+            type: "Identifier",
+            range: [2, 3],
+            name: "x"
+          },
+          kind: "init",
+          value: {
+            type: "AssignmentPattern",
+            range: [6, 7],
+            operator: "=",
+            left: {
+              type: "Identifier",
+              range: [2, 3],
+              name: "x"
+            },
+            right: {
+              type: "Literal",
+              range: [6, 7],
+              value: 0
+            }
+          }
+        }]
+      },
+      right: {
+        type: "Identifier",
+        range: [11, 14],
+        name: "obj"
+      }
+    }
+  }]
+}, {
+  ecmaVersion: 6,
+  ranges: true,
+  loose: false
+});
+
+test("({x = 0}) => x", {
+  type: "Program",
+  range: [0, 14],
+  body: [{
+    type: "ExpressionStatement",
+    range: [0, 14],
+    expression: {
+      type: "ArrowFunctionExpression",
+      range: [0, 14],
+      id: null,
+      generator: false,
+      expression: true,
+      params: [{
+        type: "ObjectPattern",
+        range: [1, 8],
+        properties: [{
+          type: "Property",
+          range: [2, 7],
+          method: false,
+          shorthand: true,
+          computed: false,
+          key: {
+            type: "Identifier",
+            range: [2, 3],
+            name: "x"
+          },
+          kind: "init",
+          value: {
+            type: "AssignmentPattern",
+            range: [6, 7],
+            operator: "=",
+            left: {
+              type: "Identifier",
+              range: [2, 3],
+              name: "x"
+            },
+            right: {
+              type: "Literal",
+              range: [6, 7],
+              value: 0
+            }
+          }
+        }]
+      }],
+      body: {
+        type: "Identifier",
+        range: [13, 14],
+        name: "x"
+      }
+    }
+  }]
+}, {
+  ecmaVersion: 6,
+  ranges: true,
+  loose: false
+});
+
+test("[a, {b: {c = 1}}] = arr", {
+  type: "Program",
+  range: [0, 23],
+  body: [{
+    type: "ExpressionStatement",
+    range: [0, 23],
+    expression: {
+      type: "AssignmentExpression",
+      range: [0, 23],
+      operator: "=",
+      left: {
+        type: "ArrayPattern",
+        range: [0, 17],
+        elements: [
+          {
+            type: "Identifier",
+            range: [1, 2],
+            name: "a"
+          },
+          {
+            type: "ObjectPattern",
+            range: [4, 16],
+            properties: [{
+              type: "Property",
+              range: [5, 15],
+              method: false,
+              shorthand: false,
+              computed: false,
+              key: {
+                type: "Identifier",
+                range: [5, 6],
+                name: "b"
+              },
+              value: {
+                type: "ObjectPattern",
+                range: [8, 15],
+                properties: [{
+                  type: "Property",
+                  range: [9, 14],
+                  method: false,
+                  shorthand: true,
+                  computed: false,
+                  key: {
+                    type: "Identifier",
+                    range: [9, 10],
+                    name: "c"
+                  },
+                  kind: "init",
+                  value: {
+                    type: "AssignmentPattern",
+                    range: [13, 14],
+                    operator: "=",
+                    left: {
+                      type: "Identifier",
+                      range: [9, 10],
+                      name: "c"
+                    },
+                    right: {
+                      type: "Literal",
+                      range: [13, 14],
+                      value: 1
+                    }
+                  }
+                }]
+              },
+              kind: "init"
+            }]
+          }
+        ]
+      },
+      right: {
+        type: "Identifier",
+        range: [20, 23],
+        name: "arr"
+      }
+    }
+  }]
+}, {
+  ecmaVersion: 6,
+  ranges: true,
+  loose: false
+});
+
+test("for ({x = 0} in arr);", {
+  type: "Program",
+  range: [0, 21],
+  body: [{
+    type: "ForInStatement",
+    range: [0, 21],
+    left: {
+      type: "ObjectPattern",
+      range: [5, 12],
+      properties: [{
+        type: "Property",
+        range: [6, 11],
+        method: false,
+        shorthand: true,
+        computed: false,
+        key: {
+          type: "Identifier",
+          range: [6, 7],
+          name: "x"
+        },
+        kind: "init",
+        value: {
+          type: "AssignmentPattern",
+          range: [10, 11],
+          operator: "=",
+          left: {
+            type: "Identifier",
+            range: [6, 7],
+            name: "x"
+          },
+          right: {
+            type: "Literal",
+            range: [10, 11],
+            value: 0
+          }
+        }
+      }]
+    },
+    right: {
+      type: "Identifier",
+      range: [16, 19],
+      name: "arr"
+    },
+    body: {
+      type: "EmptyStatement",
+      range: [20, 21]
+    }
+  }]
+}, {
+  ecmaVersion: 6,
+  ranges: true,
+  loose: false
+});
+
+testFail("obj = {x = 0}", "Unexpected token (1:9)", {ecmaVersion: 6});
+
+testFail("f({x = 0})", "Unexpected token (1:5)", {ecmaVersion: 6});
+
 // https://github.com/marijnh/acorn/issues/191
 
 test("try {} catch ({message}) {}", {

From cdd444eff12a4e6eb0744606ce12d6b6043133b6 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Sat, 24 Jan 2015 02:24:55 +0200
Subject: [PATCH 13/14] Speed-up reading words, strings and templates.

Now identifiers and strings even with escaped chars are read
in optimized way by reading entire chunks delimited by escape
chars (and not bailing to deopt mode on first one).
---
 acorn.js | 61 +++++++++++++++++++++++++++++---------------------------
 1 file changed, 32 insertions(+), 29 deletions(-)

diff --git a/acorn.js b/acorn.js
index 01f7037033..91284e04ac 100644
--- a/acorn.js
+++ b/acorn.js
@@ -1119,36 +1119,33 @@
   }
 
   function readString(quote) {
-    ++tokPos;
-    var out = "";
+    var out = "", chunkStart = ++tokPos;
     for (;;) {
       if (tokPos >= inputLen) raise(tokStart, "Unterminated string constant");
       var ch = input.charCodeAt(tokPos);
-      if (ch === quote) {
-        ++tokPos;
-        return finishToken(_string, out);
-      }
+      if (ch === quote) break;
       if (ch === 92) { // '\'
+        out += input.slice(chunkStart, tokPos);
         out += readEscapedChar();
+        chunkStart = tokPos;
       } else {
+        if (isNewLine(ch)) raise(tokStart, "Unterminated string constant");
         ++tokPos;
-        if (isNewLine(ch)) {
-          raise(tokStart, "Unterminated string constant");
-        }
-        out += String.fromCharCode(ch); // '\'
       }
     }
+    out += input.slice(chunkStart, tokPos++);
+    return finishToken(_string, out);
   }
 
   // Reads template string tokens.
 
   function readTmplToken() {
-    var out = "", start = tokPos;
+    var out = "", chunkStart = tokPos;
     for (;;) {
       if (tokPos >= inputLen) raise(tokStart, "Unterminated template");
       var ch = input.charCodeAt(tokPos);
       if (ch === 96 || ch === 36 && input.charCodeAt(tokPos + 1) === 123) { // '`', '${'
-        if (tokPos === start && tokType === _template) {
+        if (tokPos === tokStart && tokType === _template) {
           if (ch === 36) {
             tokPos += 2;
             return finishToken(_dollarBraceL);
@@ -1157,23 +1154,29 @@
             return finishToken(_backQuote);
           }
         }
+        out += input.slice(chunkStart, tokPos);
         return finishToken(_template, out);
       }
       if (ch === 92) { // '\'
+        out += input.slice(chunkStart, tokPos);
         out += readEscapedChar();
+        chunkStart = tokPos;
+      } else if (isNewLine(ch)) {
+        out += input.slice(chunkStart, tokPos);
+        ++tokPos;
+        if (ch === 13 && input.charCodeAt(tokPos) === 10) {
+          ++tokPos;
+          out += "\n";
+        } else {
+          out += String.fromCharCode(ch);
+        }
+        if (options.locations) {
+          ++tokCurLine;
+          tokLineStart = tokPos;
+        }
+        chunkStart = tokPos;
       } else {
         ++tokPos;
-        if (isNewLine(ch)) {
-          if (ch === 13 && input.charCodeAt(tokPos) === 10) {
-            ++tokPos;
-            ch = 10;
-          }
-          if (options.locations) {
-            ++tokCurLine;
-            tokLineStart = tokPos;
-          }
-        }
-        out += String.fromCharCode(ch);
       }
     }
   }
@@ -1228,20 +1231,19 @@
   // Read an identifier, and return it as a string. Sets `containsEsc`
   // to whether the word contained a '\u' escape.
   //
-  // Only builds up the word character-by-character when it actually
-  // containeds an escape, as a micro-optimization.
+  // Incrementally adds only escaped chars, adding other chunks as-is
+  // as a micro-optimization.
 
   function readWord1() {
     containsEsc = false;
-    var word, first = true, start = tokPos;
+    var word = "", first = true, chunkStart = tokPos;
     for (;;) {
       var ch = input.charCodeAt(tokPos);
       if (isIdentifierChar(ch)) {
-        if (containsEsc) word += input.charAt(tokPos);
         ++tokPos;
       } else if (ch === 92) { // "\"
-        if (!containsEsc) word = input.slice(start, tokPos);
         containsEsc = true;
+        word += input.slice(chunkStart, tokPos);
         if (input.charCodeAt(++tokPos) != 117) // "u"
           raise(tokPos, "Expecting Unicode escape sequence \\uXXXX");
         ++tokPos;
@@ -1251,12 +1253,13 @@
         if (!(first ? isIdentifierStart(esc) : isIdentifierChar(esc)))
           raise(tokPos - 4, "Invalid Unicode escape");
         word += escStr;
+        chunkStart = tokPos;
       } else {
         break;
       }
       first = false;
     }
-    return containsEsc ? word : input.slice(start, tokPos);
+    return word + input.slice(chunkStart, tokPos);
   }
 
   // Read an identifier or keyword token. Will check for reserved

From 5d96bbd781538b14d61bb1259a446317520fc0ba Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Sat, 24 Jan 2015 13:38:14 +0200
Subject: [PATCH 14/14] Simplify & fix rest argument validity checks.

---
 acorn.js              | 23 +++++++++++------------
 acorn_loose.js        |  3 ---
 test/tests-harmony.js |  3 +++
 3 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/acorn.js b/acorn.js
index 91284e04ac..847a6ba67c 100644
--- a/acorn.js
+++ b/acorn.js
@@ -315,7 +315,7 @@
   function initParserState() {
     lastStart = lastEnd = tokPos;
     if (options.locations) lastEndLoc = curPosition();
-    inFunction = inGenerator = strict = false;
+    inFunction = inGenerator = false;
     labels = [];
     skipSpace();
     readToken();
@@ -616,6 +616,7 @@
     tokType = _eof;
     tokContext = [b_stat];
     tokExprAllowed = true;
+    strict = false;
     if (tokPos === 0 && options.allowHashBang && input.slice(0, 2) === '#!') {
       skipLineComment(2);
     }
@@ -1523,8 +1524,10 @@
           break;
         case "SpreadElement":
           last.type = "RestElement";
-          toAssignable(last.argument);
-          checkSpreadAssign(last.argument);
+          var arg = last.argument;
+          toAssignable(arg);
+          if (arg.type !== "Identifier" && arg.type !== "ArrayPattern")
+            unexpected(arg.start);
           break;
         default:
           toAssignable(last);
@@ -1545,8 +1548,7 @@
   function parseRest() {
     var node = startNode();
     next();
-    node.argument = parseAssignableAtom();
-    checkSpreadAssign(node.argument);
+    node.argument = tokType === _name || tokType === _bracketL ? parseAssignableAtom() : unexpected();
     return finishNode(node, "RestElement");
   }
 
@@ -1598,13 +1600,6 @@
     return finishNode(node, "AssignmentPattern");
   }
 
-  // Checks if node can be assignable spread argument.
-
-  function checkSpreadAssign(node) {
-    if (node.type !== "Identifier" && node.type !== "ArrayPattern")
-      unexpected(node.start);
-  }
-
   // Verify that argument names are not repeated, and it does not
   // try to bind the words `eval` or `arguments`.
 
@@ -1691,7 +1686,11 @@
         break;
 
       case "AssignmentPattern":
+        checkLVal(expr.left);
+        break;
+
       case "RestElement":
+        checkLVal(expr.argument);
         break;
 
       default:
diff --git a/acorn_loose.js b/acorn_loose.js
index 297589a498..ab0c6ea709 100644
--- a/acorn_loose.js
+++ b/acorn_loose.js
@@ -325,9 +325,6 @@
   }
 
   function parseStatement() {
-    if (token.type === tt.slash || token.type === tt.assign && token.value === "/=")
-      next(true);
-
     var starttype = token.type, node = startNode();
 
     switch (starttype) {
diff --git a/test/tests-harmony.js b/test/tests-harmony.js
index 641f18657f..596e5f7ab0 100644
--- a/test/tests-harmony.js
+++ b/test/tests-harmony.js
@@ -15013,3 +15013,6 @@ testFail("if (1) let x = 10;", "Unexpected token (1:7)", {ecmaVersion: 6});
 testFail("for (;;) const x = 10;", "Unexpected token (1:9)", {ecmaVersion: 6});
 testFail("while (1) function foo(){}", "Unexpected token (1:10)", {ecmaVersion: 6});
 testFail("if (1) ; else class Cls {}", "Unexpected token (1:14)", {ecmaVersion: 6});
+
+testFail("'use strict'; [...eval] = arr", "Assigning to eval in strict mode (1:18)", {ecmaVersion: 6});
+testFail("'use strict'; ({eval = defValue} = obj)", "Assigning to eval in strict mode (1:16)", {ecmaVersion: 6});