[es6] Fix for-const loops

R=dslomov@chromium.org
BUG=3983
LOG=Y

Review URL: https://codereview.chromium.org/977543002

Cr-Commit-Position: refs/heads/master@{#26971}

src/parser.cc

@@ -3009,8 +3009,8 @@ void Parser::InitializeForEachStatement(ForEachStatement* stmt,
 }
 
 
-Statement* Parser::DesugarLetBindingsInForStatement(
-    Scope* inner_scope, ZoneList<const AstRawString*>* names,
+Statement* Parser::DesugarLexicalBindingsInForStatement(
+    Scope* inner_scope, bool is_const, ZoneList<const AstRawString*>* names,
     ForStatement* loop, Statement* init, Expression* cond, Statement* next,
     Statement* body, bool* ok) {
   // ES6 13.6.3.4 specifies that on each loop iteration the let variables are
@@ -3020,16 +3020,16 @@ Statement* Parser::DesugarLetBindingsInForStatement(
   //
   // We rewrite a for statement of the form
   //
-  //  labels: for (let x = i; cond; next) body
+  //  labels: for (let/const x = i; cond; next) body
   //
   // into
   //
   //  {
-  //    let x = i;
+  //    let/const x = i;
   //    temp_x = x;
   //    first = 1;
   //    outer: for (;;) {
-  //      let x = temp_x;
+  //      let/const x = temp_x;
   //      if (first == 1) {
   //        first = 0;
   //      } else {
@@ -3056,12 +3056,12 @@ Statement* Parser::DesugarLetBindingsInForStatement(
   Block* outer_block = factory()->NewBlock(NULL, names->length() + 3, false,
                                            RelocInfo::kNoPosition);
 
-  // Add statement: let x = i.
+  // Add statement: let/const x = i.
   outer_block->AddStatement(init, zone());
 
   const AstRawString* temp_name = ast_value_factory()->dot_for_string();
 
-  // For each let variable x:
+  // For each lexical variable x:
   //   make statement: temp_x = x.
   for (int i = 0; i < names->length(); i++) {
     VariableProxy* proxy = NewUnresolved(names->at(i), LET);
@@ -3106,16 +3106,17 @@ Statement* Parser::DesugarLetBindingsInForStatement(
   ZoneList<Variable*> inner_vars(names->length(), zone());
 
   // For each let variable x:
-  //    make statement: let x = temp_x.
+  //    make statement: let/const x = temp_x.
+  VariableMode mode = is_const ? CONST : LET;
   for (int i = 0; i < names->length(); i++) {
-    VariableProxy* proxy = NewUnresolved(names->at(i), LET);
+    VariableProxy* proxy = NewUnresolved(names->at(i), mode);
     Declaration* declaration = factory()->NewVariableDeclaration(
-        proxy, LET, scope_, RelocInfo::kNoPosition);
+        proxy, mode, scope_, RelocInfo::kNoPosition);
     Declare(declaration, true, CHECK_OK);
     inner_vars.Add(declaration->proxy()->var(), zone());
     VariableProxy* temp_proxy = factory()->NewVariableProxy(temps.at(i));
     Assignment* assignment = factory()->NewAssignment(
-        Token::INIT_LET, proxy, temp_proxy, pos);
+        is_const ? Token::INIT_CONST : Token::INIT_LET, proxy, temp_proxy, pos);
     Statement* assignment_statement =
         factory()->NewExpressionStatement(assignment, RelocInfo::kNoPosition);
     proxy->var()->set_initializer_position(init->position());
@@ -3244,8 +3245,9 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
   //   'for' '(' Expression? ';' Expression? ';' Expression? ')' Statement
 
   int stmt_pos = peek_position();
+  bool is_const = false;
   Statement* init = NULL;
-  ZoneList<const AstRawString*> let_bindings(1, zone());
+  ZoneList<const AstRawString*> lexical_bindings(1, zone());
 
   // Create an in-between scope for let-bound iteration variables.
   Scope* saved_scope = scope_;
@@ -3297,12 +3299,12 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
       }
     } else if ((peek() == Token::LET || peek() == Token::CONST) &&
                is_strict(language_mode())) {
-      bool is_const = peek() == Token::CONST;
+      is_const = peek() == Token::CONST;
       const AstRawString* name = NULL;
       VariableDeclarationProperties decl_props = kHasNoInitializers;
       Block* variable_statement =
-          ParseVariableDeclarations(kForStatement, &decl_props, &let_bindings,
-                                    &name, CHECK_OK);
+          ParseVariableDeclarations(kForStatement, &decl_props,
+                                    &lexical_bindings, &name, CHECK_OK);
       bool accept_IN = name != NULL && decl_props != kHasInitializers;
       bool accept_OF = decl_props == kHasNoInitializers;
       ForEachStatement::VisitMode mode;
@@ -3419,7 +3421,7 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
   // If there are let bindings, then condition and the next statement of the
   // for loop must be parsed in a new scope.
   Scope* inner_scope = NULL;
-  if (let_bindings.length() > 0) {
+  if (lexical_bindings.length() > 0) {
     inner_scope = NewScope(for_scope, BLOCK_SCOPE);
     inner_scope->set_start_position(scanner()->location().beg_pos);
     scope_ = inner_scope;
@@ -3442,10 +3444,11 @@ Statement* Parser::ParseForStatement(ZoneList<const AstRawString*>* labels,
   Statement* body = ParseSubStatement(NULL, CHECK_OK);
 
   Statement* result = NULL;
-  if (let_bindings.length() > 0) {
+  if (lexical_bindings.length() > 0) {
     scope_ = for_scope;
-    result = DesugarLetBindingsInForStatement(inner_scope, &let_bindings, loop,
-                                              init, cond, next, body, CHECK_OK);
+    result = DesugarLexicalBindingsInForStatement(
+                 inner_scope, is_const, &lexical_bindings, loop, init, cond,
+                 next, body, CHECK_OK);
     scope_ = saved_scope;
     for_scope->set_end_position(scanner()->location().end_pos);
   } else {

src/parser.h

@@ -763,8 +763,8 @@ class Parser : public ParserBase<ParserTraits> {
                                   Expression* each,
                                   Expression* subject,
                                   Statement* body);
-  Statement* DesugarLetBindingsInForStatement(
-      Scope* inner_scope, ZoneList<const AstRawString*>* names,
+  Statement* DesugarLexicalBindingsInForStatement(
+      Scope* inner_scope, bool is_const, ZoneList<const AstRawString*>* names,
       ForStatement* loop, Statement* init, Expression* cond, Statement* next,
       Statement* body, bool* ok);
 

test/mjsunit/es6/regress/regress-3938.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+'use strict';
+
+assertThrows(function() { for (const i = 0; ; i++) {} }, TypeError);
+assertThrows("'use strict'; for (const i = 0; ; i++) {}", TypeError);

test/mjsunit/harmony/block-const-assign.js

@@ -93,6 +93,22 @@ function constDecl9(use) {
   return "(function constvar() { " + use + "; })();";
 }
 
+// For loop variable.
+function constDecl10(use) {
+  return "(function() { for (const constvar = 0; ;) { " + use + "; } })();";
+}
+
+// For-in loop variable.
+function constDecl11(use) {
+  return "(function() { for (const constvar in {a: 1}) { " + use + "; } })();";
+}
+
+// For-of loop variable.
+function constDecl12(use) {
+  return "(function() { for (const constvar of [1]) { " + use + "; } })();";
+}
+
+
 let decls = [ constDecl0,
               constDecl1,
               constDecl2,
@@ -102,7 +118,10 @@ let decls = [ constDecl0,
               constDecl6,
               constDecl7,
               constDecl8,
-              constDecl9
+              constDecl9,
+              constDecl10,
+              constDecl11,
+              constDecl12
               ];
 let declsForTDZ = new Set([constDecl1, constDecl3, constDecl5, constDecl7]);
 let uses = [ 'constvar = 1;',