Make let variables fresh in each iteration of a for-loop.

src/parser.h

 // Copyright 2012 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.
 
 #ifndef V8_PARSER_H_
 #define V8_PARSER_H_
 
 #include "allocation.h"
 #include "ast.h"
 #include "compiler.h"  // For CachedDataMode
@@ skipping 700 matching lines @@
   DebuggerStatement* ParseDebuggerStatement(bool* ok);
 
   // Support for hamony block scoped bindings.
   Block* ParseScopedBlock(ZoneStringList* labels, bool* ok);
 
   // Initialize the components of a for-in / for-of statement.
   void InitializeForEachStatement(ForEachStatement* stmt,
                                   Expression* each,
                                   Expression* subject,
                                   Statement* body);
+  Statement* DesugarLetBindingsInForStatement(

[rossberg, 2014/05/22 12:55:44]

Nit: DesugarLexicalDeclarationInForStatement, since in fact, it might also be
const (or others).

[ulan, 2014/05/23 14:29:03]

As discussed offline, const and others are not handled here.

+      Scope* inner_scope, ZoneStringList* names, ForStatement* loop,
+      Statement* init, Expression* cond, Statement* next, bool* ok);
+  Statement* Assign(Token::Value op, VariableProxy* dst, Expression* src,

[rossberg, 2014/05/22 12:55:44]

I am not sure if it's actually worth introducing these extra functions. But if
you do, they should probably be named NewAssignmentStatement and NewTemporary
for consistency with other such helpers. Also, please then update other places
in the parser calling NewAssignmentExpression and Scope::NewTemporary to use
them consistently.

[ulan, 2014/05/23 14:29:03]

Done. Inlined the functions to be consistent.

+                    int pos = RelocInfo::kNoPosition);
+  Variable* Temporary(Handle<String> name);
 
   FunctionLiteral* ParseFunctionLiteral(
       Handle<String> name,
       Scanner::Location function_name_location,
       bool name_is_strict_reserved,
       bool is_generator,
       int function_token_position,
       FunctionLiteral::FunctionType type,
       bool* ok);
 
@@ skipping 98 matching lines @@
  private:
   static const int kLiteralTypeSlot = 0;
   static const int kElementsSlot = 1;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(CompileTimeValue);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_PARSER_H_