ecma 6 partial support: let and const

acorn.js

@@ -51,9 +51,9 @@
 
   var defaultOptions = exports.defaultOptions = {
     // `ecmaVersion` indicates the ECMAScript version to parse. Must
-    // be either 3 or 5. This
-    // influences support for strict mode, the set of reserved words, and
-    // support for getters and setter.
+    // be either 3, or 5, or 6. This
+    // influences support for strict mode, the set of reserved words,
+    // support for getters and setters and other features.
     ecmaVersion: 5,
     // Turn on `strictSemicolons` to prevent the parser from doing
     // automatic semicolon insertion.
@@ -113,6 +113,8 @@
     for (var opt in defaultOptions) if (!Object.prototype.hasOwnProperty.call(options, opt))
       options[opt] = defaultOptions[opt];
     sourceFile = options.sourceFile || null;
+
+    isKeyword = options.ecmaVersion >= 6 ? isEcma6Keyword : isEcma5AndLessKeyword;
   }
 
   // The `getLineInfo` function is mostly useful when the
@@ -276,6 +278,7 @@
   var _finally = {keyword: "finally"}, _for = {keyword: "for", isLoop: true}, _function = {keyword: "function"};
   var _if = {keyword: "if"}, _return = {keyword: "return", beforeExpr: true}, _switch = {keyword: "switch"};
   var _throw = {keyword: "throw", beforeExpr: true}, _try = {keyword: "try"}, _var = {keyword: "var"};
+  var _let = {keyword: "let"}, _const = {keyword: "const"};
   var _while = {keyword: "while", isLoop: true}, _with = {keyword: "with"}, _new = {keyword: "new", beforeExpr: true};
   var _this = {keyword: "this"};
 
@@ -296,7 +299,8 @@
                       "continue": _continue, "debugger": _debugger, "default": _default,
                       "do": _do, "else": _else, "finally": _finally, "for": _for,
                       "function": _function, "if": _if, "return": _return, "switch": _switch,
-                      "throw": _throw, "try": _try, "var": _var, "while": _while, "with": _with,
+                      "throw": _throw, "try": _try, "var": _var, "let": _let, "const": _const,
+                      "while": _while, "with": _with,
                       "null": _null, "true": _true, "false": _false, "new": _new, "in": _in,
                       "instanceof": {keyword: "instanceof", binop: 7, beforeExpr: true}, "this": _this,
                       "typeof": {keyword: "typeof", prefix: true, beforeExpr: true},
@@ -415,7 +419,13 @@
 
   // And the keywords.
 
-  var isKeyword = makePredicate("break case catch continue debugger default do else finally for function if return switch throw try var while with null true false instanceof typeof void delete new in this");
+  var ecma5AndLessKeywords = "break case catch continue debugger default do else finally for function if return switch throw try var while with null true false instanceof typeof void delete new in this";
+
+  var isEcma5AndLessKeyword = makePredicate(ecma5AndLessKeywords);
+
+  var isEcma6Keyword = makePredicate(ecma5AndLessKeywords + " let const");
+
+  var isKeyword = isEcma5AndLessKeyword;
 
   // ## Character categories
 
@@ -1207,10 +1217,11 @@
       labels.push(loopLabel);
       expect(_parenL);
       if (tokType === _semi) return parseFor(node, null);
-      if (tokType === _var) {
+      if (tokType === _var || tokType === _let) {
+        var varKind = tokType.keyword;
         var init = startNode();
         next();
-        parseVar(init, true);
+        parseVar(init, true, varKind);
         finishNode(init, "VariableDeclaration");
         if (init.declarations.length === 1 && eat(_in))
           return parseForIn(node, init);
@@ -1308,9 +1319,11 @@
         raise(node.start, "Missing catch or finally clause");
       return finishNode(node, "TryStatement");
 
+    case _const:
+    case _let:
     case _var:
       next();
-      parseVar(node);
+      parseVar(node, false, starttype.keyword);
       semicolon();
       return finishNode(node, "VariableDeclaration");
 
@@ -1421,15 +1434,15 @@
 
   // Parse a list of variable declarations.
 
-  function parseVar(node, noIn) {
+  function parseVar(node, noIn, kind) {
     node.declarations = [];
-    node.kind = "var";
+    node.kind = kind;
     for (;;) {
       var decl = startNode();
       decl.id = parseIdent();
       if (strict && isStrictBadIdWord(decl.id.name))
         raise(decl.id.start, "Binding " + decl.id.name + " in strict mode");
-      decl.init = eat(_eq) ? parseExpression(true, noIn) : null;
+      decl.init = eat(_eq) ? parseExpression(true, noIn) : (kind === _const.keyword ? unexpected() : null);
       node.declarations.push(finishNode(decl, "VariableDeclarator"));
       if (!eat(_comma)) break;
     }

index.html

@@ -34,9 +34,9 @@ API</a>, with the caveat that the SpiderMonkey-specific syntax
     <span class="k">return</span> <span class="nx">parseTopLevel</span><span class="p">(</span><span class="nx">options</span><span class="p">.</span><span class="nx">program</span><span class="p">);</span>
   <span class="p">};</span></pre></div>             </td>           </tr>                               <tr id="section-3">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-3">&#182;</a>               </div>               <p>A second optional argument can be given to further configure
 the parser process. These options are recognized:</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">defaultOptions</span> <span class="o">=</span> <span class="nx">exports</span><span class="p">.</span><span class="nx">defaultOptions</span> <span class="o">=</span> <span class="p">{</span></pre></div>             </td>           </tr>                               <tr id="section-4">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-4">&#182;</a>               </div>               <p><code>ecmaVersion</code> indicates the ECMAScript version to parse. Must
-be either 3 or 5. This
-influences support for strict mode, the set of reserved words, and
-support for getters and setter.</p>             </td>             <td class="code">               <div class="highlight"><pre>    <span class="nx">ecmaVersion</span><span class="o">:</span> <span class="mi">5</span><span class="p">,</span></pre></div>             </td>           </tr>                               <tr id="section-5">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-5">&#182;</a>               </div>               <p>Turn on <code>strictSemicolons</code> to prevent the parser from doing
+be either 3, or 5, or 6. This
+influences support for strict mode, the set of reserved words,
+support for getters and setters and other features.</p>             </td>             <td class="code">               <div class="highlight"><pre>    <span class="nx">ecmaVersion</span><span class="o">:</span> <span class="mi">5</span><span class="p">,</span></pre></div>             </td>           </tr>                               <tr id="section-5">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-5">&#182;</a>               </div>               <p>Turn on <code>strictSemicolons</code> to prevent the parser from doing
 automatic semicolon insertion.</p>             </td>             <td class="code">               <div class="highlight"><pre>    <span class="nx">strictSemicolons</span><span class="o">:</span> <span class="kc">false</span><span class="p">,</span></pre></div>             </td>           </tr>                               <tr id="section-6">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-6">&#182;</a>               </div>               <p>When <code>allowTrailingCommas</code> is false, the parser will not allow
 trailing commas in array and object literals.</p>             </td>             <td class="code">               <div class="highlight"><pre>    <span class="nx">allowTrailingCommas</span><span class="o">:</span> <span class="kc">true</span><span class="p">,</span></pre></div>             </td>           </tr>                               <tr id="section-7">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-7">&#182;</a>               </div>               <p>By default, reserved words are not enforced. Enable
 <code>forbidReserved</code> to enforce them. When this option has the
@@ -73,6 +73,8 @@ file in every node's <code>loc</code> object.</p>             </td>
     <span class="k">for</span> <span class="p">(</span><span class="kd">var</span> <span class="nx">opt</span> <span class="k">in</span> <span class="nx">defaultOptions</span><span class="p">)</span> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nb">Object</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">hasOwnProperty</span><span class="p">.</span><span class="nx">call</span><span class="p">(</span><span class="nx">options</span><span class="p">,</span> <span class="nx">opt</span><span class="p">))</span>
       <span class="nx">options</span><span class="p">[</span><span class="nx">opt</span><span class="p">]</span> <span class="o">=</span> <span class="nx">defaultOptions</span><span class="p">[</span><span class="nx">opt</span><span class="p">];</span>
     <span class="nx">sourceFile</span> <span class="o">=</span> <span class="nx">options</span><span class="p">.</span><span class="nx">sourceFile</span> <span class="o">||</span> <span class="kc">null</span><span class="p">;</span>
+
+    <span class="nx">isKeyword</span> <span class="o">=</span> <span class="nx">options</span><span class="p">.</span><span class="nx">ecmaVersion</span> <span class="o">&gt;=</span> <span class="mi">6</span> <span class="o">?</span> <span class="nx">isEcma6Keyword</span> <span class="o">:</span> <span class="nx">isEcma5AndLessKeyword</span><span class="p">;</span>
   <span class="p">}</span></pre></div>             </td>           </tr>                               <tr id="section-15">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-15">&#182;</a>               </div>               <p>The <code>getLineInfo</code> function is mostly useful when the
 <code>locations</code> option is off (for performance reasons) and you
 want to find the line/column position for a given character
@@ -172,6 +174,7 @@ continue jumps to that label.</p>             </td>             <td class="code"
   <span class="kd">var</span> <span class="nx">_finally</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;finally&quot;</span><span class="p">},</span> <span class="nx">_for</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;for&quot;</span><span class="p">,</span> <span class="nx">isLoop</span><span class="o">:</span> <span class="kc">true</span><span class="p">},</span> <span class="nx">_function</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;function&quot;</span><span class="p">};</span>
   <span class="kd">var</span> <span class="nx">_if</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;if&quot;</span><span class="p">},</span> <span class="nx">_return</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;return&quot;</span><span class="p">,</span> <span class="nx">beforeExpr</span><span class="o">:</span> <span class="kc">true</span><span class="p">},</span> <span class="nx">_switch</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;switch&quot;</span><span class="p">};</span>
   <span class="kd">var</span> <span class="nx">_throw</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;throw&quot;</span><span class="p">,</span> <span class="nx">beforeExpr</span><span class="o">:</span> <span class="kc">true</span><span class="p">},</span> <span class="nx">_try</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;try&quot;</span><span class="p">},</span> <span class="nx">_var</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;var&quot;</span><span class="p">};</span>
+  <span class="kd">var</span> <span class="nx">_let</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;let&quot;</span><span class="p">},</span> <span class="nx">_const</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;const&quot;</span><span class="p">};</span>
   <span class="kd">var</span> <span class="nx">_while</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;while&quot;</span><span class="p">,</span> <span class="nx">isLoop</span><span class="o">:</span> <span class="kc">true</span><span class="p">},</span> <span class="nx">_with</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;with&quot;</span><span class="p">},</span> <span class="nx">_new</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;new&quot;</span><span class="p">,</span> <span class="nx">beforeExpr</span><span class="o">:</span> <span class="kc">true</span><span class="p">};</span>
   <span class="kd">var</span> <span class="nx">_this</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;this&quot;</span><span class="p">};</span></pre></div>             </td>           </tr>                               <tr id="section-33">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-33">&#182;</a>               </div>               <p>The keywords that denote values.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">_null</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;null&quot;</span><span class="p">,</span> <span class="nx">atomValue</span><span class="o">:</span> <span class="kc">null</span><span class="p">},</span> <span class="nx">_true</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;true&quot;</span><span class="p">,</span> <span class="nx">atomValue</span><span class="o">:</span> <span class="kc">true</span><span class="p">};</span>
   <span class="kd">var</span> <span class="nx">_false</span> <span class="o">=</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;false&quot;</span><span class="p">,</span> <span class="nx">atomValue</span><span class="o">:</span> <span class="kc">false</span><span class="p">};</span></pre></div>             </td>           </tr>                               <tr id="section-34">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-34">&#182;</a>               </div>               <p>Some keywords are treated as regular operators. <code>in</code> sometimes
@@ -180,7 +183,8 @@ we assign a variable name to it for quick comparing.</p>             </td>
                       <span class="s2">&quot;continue&quot;</span><span class="o">:</span> <span class="nx">_continue</span><span class="p">,</span> <span class="s2">&quot;debugger&quot;</span><span class="o">:</span> <span class="nx">_debugger</span><span class="p">,</span> <span class="s2">&quot;default&quot;</span><span class="o">:</span> <span class="nx">_default</span><span class="p">,</span>
                       <span class="s2">&quot;do&quot;</span><span class="o">:</span> <span class="nx">_do</span><span class="p">,</span> <span class="s2">&quot;else&quot;</span><span class="o">:</span> <span class="nx">_else</span><span class="p">,</span> <span class="s2">&quot;finally&quot;</span><span class="o">:</span> <span class="nx">_finally</span><span class="p">,</span> <span class="s2">&quot;for&quot;</span><span class="o">:</span> <span class="nx">_for</span><span class="p">,</span>
                       <span class="s2">&quot;function&quot;</span><span class="o">:</span> <span class="nx">_function</span><span class="p">,</span> <span class="s2">&quot;if&quot;</span><span class="o">:</span> <span class="nx">_if</span><span class="p">,</span> <span class="s2">&quot;return&quot;</span><span class="o">:</span> <span class="nx">_return</span><span class="p">,</span> <span class="s2">&quot;switch&quot;</span><span class="o">:</span> <span class="nx">_switch</span><span class="p">,</span>
-                      <span class="s2">&quot;throw&quot;</span><span class="o">:</span> <span class="nx">_throw</span><span class="p">,</span> <span class="s2">&quot;try&quot;</span><span class="o">:</span> <span class="nx">_try</span><span class="p">,</span> <span class="s2">&quot;var&quot;</span><span class="o">:</span> <span class="nx">_var</span><span class="p">,</span> <span class="s2">&quot;while&quot;</span><span class="o">:</span> <span class="nx">_while</span><span class="p">,</span> <span class="s2">&quot;with&quot;</span><span class="o">:</span> <span class="nx">_with</span><span class="p">,</span>
+                      <span class="s2">&quot;throw&quot;</span><span class="o">:</span> <span class="nx">_throw</span><span class="p">,</span> <span class="s2">&quot;try&quot;</span><span class="o">:</span> <span class="nx">_try</span><span class="p">,</span> <span class="s2">&quot;var&quot;</span><span class="o">:</span> <span class="nx">_var</span><span class="p">,</span> <span class="s2">&quot;let&quot;</span><span class="o">:</span> <span class="nx">_let</span><span class="p">,</span> <span class="s2">&quot;const&quot;</span><span class="o">:</span> <span class="nx">_const</span><span class="p">,</span>
+                      <span class="s2">&quot;while&quot;</span><span class="o">:</span> <span class="nx">_while</span><span class="p">,</span> <span class="s2">&quot;with&quot;</span><span class="o">:</span> <span class="nx">_with</span><span class="p">,</span>
                       <span class="s2">&quot;null&quot;</span><span class="o">:</span> <span class="nx">_null</span><span class="p">,</span> <span class="s2">&quot;true&quot;</span><span class="o">:</span> <span class="nx">_true</span><span class="p">,</span> <span class="s2">&quot;false&quot;</span><span class="o">:</span> <span class="nx">_false</span><span class="p">,</span> <span class="s2">&quot;new&quot;</span><span class="o">:</span> <span class="nx">_new</span><span class="p">,</span> <span class="s2">&quot;in&quot;</span><span class="o">:</span> <span class="nx">_in</span><span class="p">,</span>
                       <span class="s2">&quot;instanceof&quot;</span><span class="o">:</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;instanceof&quot;</span><span class="p">,</span> <span class="nx">binop</span><span class="o">:</span> <span class="mi">7</span><span class="p">,</span> <span class="nx">beforeExpr</span><span class="o">:</span> <span class="kc">true</span><span class="p">},</span> <span class="s2">&quot;this&quot;</span><span class="o">:</span> <span class="nx">_this</span><span class="p">,</span>
                       <span class="s2">&quot;typeof&quot;</span><span class="o">:</span> <span class="p">{</span><span class="nx">keyword</span><span class="o">:</span> <span class="s2">&quot;typeof&quot;</span><span class="p">,</span> <span class="nx">prefix</span><span class="o">:</span> <span class="kc">true</span><span class="p">,</span> <span class="nx">beforeExpr</span><span class="o">:</span> <span class="kc">true</span><span class="p">},</span>
@@ -255,7 +259,13 @@ switch first dispatches on the lengths, to save on comparisons.</p>
       <span class="nx">compareTo</span><span class="p">(</span><span class="nx">words</span><span class="p">);</span>
     <span class="p">}</span>
     <span class="k">return</span> <span class="k">new</span> <span class="nb">Function</span><span class="p">(</span><span class="s2">&quot;str&quot;</span><span class="p">,</span> <span class="nx">f</span><span class="p">);</span>
-  <span class="p">}</span></pre></div>             </td>           </tr>                               <tr id="section-42">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-42">&#182;</a>               </div>               <p>The ECMAScript 3 reserved word list.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isReservedWord3</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;abstract boolean byte char class double enum export extends final float goto implements import int interface long native package private protected public short static super synchronized throws transient volatile&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-43">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-43">&#182;</a>               </div>               <p>ECMAScript 5 reserved words.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isReservedWord5</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;class enum extends super const export import&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-44">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-44">&#182;</a>               </div>               <p>The additional reserved words in strict mode.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isStrictReservedWord</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;implements interface let package private protected public static yield&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-45">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-45">&#182;</a>               </div>               <p>The forbidden variable names in strict mode.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isStrictBadIdWord</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;eval arguments&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-46">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-46">&#182;</a>               </div>               <p>And the keywords.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isKeyword</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;break case catch continue debugger default do else finally for function if return switch throw try var while with null true false instanceof typeof void delete new in this&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-47">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-47">&#182;</a>               </div>               <h2>Character categories</h2>             </td>             <td class="code">               <div class="highlight"><pre></pre></div>             </td>           </tr>                               <tr id="section-48">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-48">&#182;</a>               </div>               <p>Big ugly regular expressions that match characters in the
+  <span class="p">}</span></pre></div>             </td>           </tr>                               <tr id="section-42">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-42">&#182;</a>               </div>               <p>The ECMAScript 3 reserved word list.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isReservedWord3</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;abstract boolean byte char class double enum export extends final float goto implements import int interface long native package private protected public short static super synchronized throws transient volatile&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-43">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-43">&#182;</a>               </div>               <p>ECMAScript 5 reserved words.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isReservedWord5</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;class enum extends super const export import&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-44">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-44">&#182;</a>               </div>               <p>The additional reserved words in strict mode.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isStrictReservedWord</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;implements interface let package private protected public static yield&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-45">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-45">&#182;</a>               </div>               <p>The forbidden variable names in strict mode.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">isStrictBadIdWord</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="s2">&quot;eval arguments&quot;</span><span class="p">);</span></pre></div>             </td>           </tr>                               <tr id="section-46">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-46">&#182;</a>               </div>               <p>And the keywords.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">ecma5AndLessKeywords</span> <span class="o">=</span> <span class="s2">&quot;break case catch continue debugger default do else finally for function if return switch throw try var while with null true false instanceof typeof void delete new in this&quot;</span><span class="p">;</span>
+
+  <span class="kd">var</span> <span class="nx">isEcma5AndLessKeyword</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="nx">ecma5AndLessKeywords</span><span class="p">);</span>
+
+  <span class="kd">var</span> <span class="nx">isEcma6Keyword</span> <span class="o">=</span> <span class="nx">makePredicate</span><span class="p">(</span><span class="nx">ecma5AndLessKeywords</span> <span class="o">+</span> <span class="s2">&quot; let const&quot;</span><span class="p">);</span>
+
+  <span class="kd">var</span> <span class="nx">isKeyword</span> <span class="o">=</span> <span class="nx">isEcma5AndLessKeyword</span><span class="p">;</span></pre></div>             </td>           </tr>                               <tr id="section-47">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-47">&#182;</a>               </div>               <h2>Character categories</h2>             </td>             <td class="code">               <div class="highlight"><pre></pre></div>             </td>           </tr>                               <tr id="section-48">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-48">&#182;</a>               </div>               <p>Big ugly regular expressions that match characters in the
 whitespace, identifier, and identifier-start categories. These
 are only applied when a character is found to actually have a
 code point above 128.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">var</span> <span class="nx">nonASCIIwhitespace</span> <span class="o">=</span> <span class="sr">/[\u1680\u180e\u2000-\u200a\u202f\u205f\u3000\ufeff]/</span><span class="p">;</span>
@@ -865,10 +875,11 @@ a regular <code>for</code> loop.</p>             </td>             <td class="co
       <span class="nx">labels</span><span class="p">.</span><span class="nx">push</span><span class="p">(</span><span class="nx">loopLabel</span><span class="p">);</span>
       <span class="nx">expect</span><span class="p">(</span><span class="nx">_parenL</span><span class="p">);</span>
       <span class="k">if</span> <span class="p">(</span><span class="nx">tokType</span> <span class="o">===</span> <span class="nx">_semi</span><span class="p">)</span> <span class="k">return</span> <span class="nx">parseFor</span><span class="p">(</span><span class="nx">node</span><span class="p">,</span> <span class="kc">null</span><span class="p">);</span>
-      <span class="k">if</span> <span class="p">(</span><span class="nx">tokType</span> <span class="o">===</span> <span class="nx">_var</span><span class="p">)</span> <span class="p">{</span>
+      <span class="k">if</span> <span class="p">(</span><span class="nx">tokType</span> <span class="o">===</span> <span class="nx">_var</span> <span class="o">||</span> <span class="nx">tokType</span> <span class="o">===</span> <span class="nx">_let</span><span class="p">)</span> <span class="p">{</span>
+        <span class="kd">var</span> <span class="nx">varKind</span> <span class="o">=</span> <span class="nx">tokType</span><span class="p">.</span><span class="nx">keyword</span><span class="p">;</span>
         <span class="kd">var</span> <span class="nx">init</span> <span class="o">=</span> <span class="nx">startNode</span><span class="p">();</span>
         <span class="nx">next</span><span class="p">();</span>
-        <span class="nx">parseVar</span><span class="p">(</span><span class="nx">init</span><span class="p">,</span> <span class="kc">true</span><span class="p">);</span>
+        <span class="nx">parseVar</span><span class="p">(</span><span class="nx">init</span><span class="p">,</span> <span class="kc">true</span><span class="p">,</span> <span class="nx">varKind</span><span class="p">);</span>
         <span class="nx">finishNode</span><span class="p">(</span><span class="nx">init</span><span class="p">,</span> <span class="s2">&quot;VariableDeclaration&quot;</span><span class="p">);</span>
         <span class="k">if</span> <span class="p">(</span><span class="nx">init</span><span class="p">.</span><span class="nx">declarations</span><span class="p">.</span><span class="nx">length</span> <span class="o">===</span> <span class="mi">1</span> <span class="o">&amp;&amp;</span> <span class="nx">eat</span><span class="p">(</span><span class="nx">_in</span><span class="p">))</span>
           <span class="k">return</span> <span class="nx">parseForIn</span><span class="p">(</span><span class="nx">node</span><span class="p">,</span> <span class="nx">init</span><span class="p">);</span>
@@ -958,9 +969,11 @@ adding statements to.</p>             </td>             <td class="code">
         <span class="nx">raise</span><span class="p">(</span><span class="nx">node</span><span class="p">.</span><span class="nx">start</span><span class="p">,</span> <span class="s2">&quot;Missing catch or finally clause&quot;</span><span class="p">);</span>
       <span class="k">return</span> <span class="nx">finishNode</span><span class="p">(</span><span class="nx">node</span><span class="p">,</span> <span class="s2">&quot;TryStatement&quot;</span><span class="p">);</span>
 
+    <span class="k">case</span> <span class="nx">_const</span><span class="o">:</span>
+    <span class="k">case</span> <span class="nx">_let</span><span class="o">:</span>
     <span class="k">case</span> <span class="nx">_var</span><span class="o">:</span>
       <span class="nx">next</span><span class="p">();</span>
-      <span class="nx">parseVar</span><span class="p">(</span><span class="nx">node</span><span class="p">);</span>
+      <span class="nx">parseVar</span><span class="p">(</span><span class="nx">node</span><span class="p">,</span> <span class="kc">false</span><span class="p">,</span> <span class="nx">starttype</span><span class="p">.</span><span class="nx">keyword</span><span class="p">);</span>
       <span class="nx">semicolon</span><span class="p">();</span>
       <span class="k">return</span> <span class="nx">finishNode</span><span class="p">(</span><span class="nx">node</span><span class="p">,</span> <span class="s2">&quot;VariableDeclaration&quot;</span><span class="p">);</span>
 
@@ -1047,15 +1060,15 @@ expression.</p>             </td>             <td class="code">               <d
     <span class="nx">node</span><span class="p">.</span><span class="nx">body</span> <span class="o">=</span> <span class="nx">parseStatement</span><span class="p">();</span>
     <span class="nx">labels</span><span class="p">.</span><span class="nx">pop</span><span class="p">();</span>
     <span class="k">return</span> <span class="nx">finishNode</span><span class="p">(</span><span class="nx">node</span><span class="p">,</span> <span class="s2">&quot;ForInStatement&quot;</span><span class="p">);</span>
-  <span class="p">}</span></pre></div>             </td>           </tr>                               <tr id="section-107">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-107">&#182;</a>               </div>               <p>Parse a list of variable declarations.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">function</span> <span class="nx">parseVar</span><span class="p">(</span><span class="nx">node</span><span class="p">,</span> <span class="nx">noIn</span><span class="p">)</span> <span class="p">{</span>
+  <span class="p">}</span></pre></div>             </td>           </tr>                               <tr id="section-107">             <td class="docs">               <div class="pilwrap">                 <a class="pilcrow" href="#section-107">&#182;</a>               </div>               <p>Parse a list of variable declarations.</p>             </td>             <td class="code">               <div class="highlight"><pre>  <span class="kd">function</span> <span class="nx">parseVar</span><span class="p">(</span><span class="nx">node</span><span class="p">,</span> <span class="nx">noIn</span><span class="p">,</span> <span class="nx">kind</span><span class="p">)</span> <span class="p">{</span>
     <span class="nx">node</span><span class="p">.</span><span class="nx">declarations</span> <span class="o">=</span> <span class="p">[];</span>
-    <span class="nx">node</span><span class="p">.</span><span class="nx">kind</span> <span class="o">=</span> <span class="s2">&quot;var&quot;</span><span class="p">;</span>
+    <span class="nx">node</span><span class="p">.</span><span class="nx">kind</span> <span class="o">=</span> <span class="nx">kind</span><span class="p">;</span>
     <span class="k">for</span> <span class="p">(;;)</span> <span class="p">{</span>
       <span class="kd">var</span> <span class="nx">decl</span> <span class="o">=</span> <span class="nx">startNode</span><span class="p">();</span>
       <span class="nx">decl</span><span class="p">.</span><span class="nx">id</span> <span class="o">=</span> <span class="nx">parseIdent</span><span class="p">();</span>
       <span class="k">if</span> <span class="p">(</span><span class="nx">strict</span> <span class="o">&amp;&amp;</span> <span class="nx">isStrictBadIdWord</span><span class="p">(</span><span class="nx">decl</span><span class="p">.</span><span class="nx">id</span><span class="p">.</span><span class="nx">name</span><span class="p">))</span>
         <span class="nx">raise</span><span class="p">(</span><span class="nx">decl</span><span class="p">.</span><span class="nx">id</span><span class="p">.</span><span class="nx">start</span><span class="p">,</span> <span class="s2">&quot;Binding &quot;</span> <span class="o">+</span> <span class="nx">decl</span><span class="p">.</span><span class="nx">id</span><span class="p">.</span><span class="nx">name</span> <span class="o">+</span> <span class="s2">&quot; in strict mode&quot;</span><span class="p">);</span>
-      <span class="nx">decl</span><span class="p">.</span><span class="nx">init</span> <span class="o">=</span> <span class="nx">eat</span><span class="p">(</span><span class="nx">_eq</span><span class="p">)</span> <span class="o">?</span> <span class="nx">parseExpression</span><span class="p">(</span><span class="kc">true</span><span class="p">,</span> <span class="nx">noIn</span><span class="p">)</span> <span class="o">:</span> <span class="kc">null</span><span class="p">;</span>
+      <span class="nx">decl</span><span class="p">.</span><span class="nx">init</span> <span class="o">=</span> <span class="nx">eat</span><span class="p">(</span><span class="nx">_eq</span><span class="p">)</span> <span class="o">?</span> <span class="nx">parseExpression</span><span class="p">(</span><span class="kc">true</span><span class="p">,</span> <span class="nx">noIn</span><span class="p">)</span> <span class="o">:</span> <span class="p">(</span><span class="nx">kind</span> <span class="o">===</span> <span class="nx">_const</span><span class="p">.</span><span class="nx">keyword</span> <span class="o">?</span> <span class="nx">unexpected</span><span class="p">()</span> <span class="o">:</span> <span class="kc">null</span><span class="p">);</span>
       <span class="nx">node</span><span class="p">.</span><span class="nx">declarations</span><span class="p">.</span><span class="nx">push</span><span class="p">(</span><span class="nx">finishNode</span><span class="p">(</span><span class="nx">decl</span><span class="p">,</span> <span class="s2">&quot;VariableDeclarator&quot;</span><span class="p">));</span>
       <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="nx">eat</span><span class="p">(</span><span class="nx">_comma</span><span class="p">))</span> <span class="k">break</span><span class="p">;</span>
     <span class="p">}</span>