Let bound iteration variables in for-loops

src/preparser.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 294 matching lines @@
 
 
 PreParser::Statement PreParser::ParseVariableStatement(
     VariableDeclarationContext var_context,
     bool* ok) {
   // VariableStatement ::
   //   VariableDeclarations ';'
 
   Statement result = ParseVariableDeclarations(var_context,
                                                NULL,
+                                               NULL,
                                                CHECK_OK);
   ExpectSemicolon(CHECK_OK);
   return result;
 }
 
 
 // If the variable declaration declares exactly one non-const
 // variable, then *var is set to that variable. In all other cases,
 // *var is untouched; in particular, it is the caller's responsibility
 // to initialize it properly. This mechanism is also used for the parsing
 // of 'for-in' loops.
 PreParser::Statement PreParser::ParseVariableDeclarations(
     VariableDeclarationContext var_context,
+    VariableDeclarationProperties* decl_props,
     int* num_decl,
     bool* ok) {
   // VariableDeclarations ::
   //   ('var' | 'const') (Identifier ('=' AssignmentExpression)?)+[',']
 
   if (peek() == i::Token::VAR) {
     Consume(i::Token::VAR);
   } else if (peek() == i::Token::CONST) {
     if (strict_mode()) {
       i::Scanner::Location location = scanner_->peek_location();
@@ skipping 30 matching lines @@
       StrictModeIdentifierViolation(scanner_->location(),
                                     "strict_var_name",
                                     identifier,
                                     ok);
       return Statement::Default();
     }
     nvars++;
     if (peek() == i::Token::ASSIGN) {
       Expect(i::Token::ASSIGN, CHECK_OK);
       ParseAssignmentExpression(var_context != kForStatement, CHECK_OK);
+      if (decl_props != NULL) *decl_props = kHasInitializers;
     }
   } while (peek() == i::Token::COMMA);
 
   if (num_decl != NULL) *num_decl = nvars;
   return Statement::Default();
 }
 
 
 PreParser::Statement PreParser::ParseExpressionOrLabelledStatement(bool* ok) {
   // ExpressionStatement | LabelledStatement ::
@@ skipping 174 matching lines @@
 
 PreParser::Statement PreParser::ParseForStatement(bool* ok) {
   // ForStatement ::
   //   'for' '(' Expression? ';' Expression? ';' Expression? ')' Statement
 
   Expect(i::Token::FOR, CHECK_OK);
   Expect(i::Token::LPAREN, CHECK_OK);
   if (peek() != i::Token::SEMICOLON) {
     if (peek() == i::Token::VAR || peek() == i::Token::CONST ||
         peek() == i::Token::LET) {
+      bool is_let = peek() == i::Token::LET;
       int decl_count;
-      ParseVariableDeclarations(kForStatement, &decl_count, CHECK_OK);
-      if (peek() == i::Token::IN && decl_count == 1) {
+      VariableDeclarationProperties decl_props = kHasNoInitializers;
+      ParseVariableDeclarations(
+          kForStatement, &decl_props, &decl_count, CHECK_OK);
+      bool accept_IN = decl_count == 1 &&
+          !(is_let && decl_props == kHasInitializers);
+      if (peek() == i::Token::IN && accept_IN) {
         Expect(i::Token::IN, CHECK_OK);
         ParseExpression(true, CHECK_OK);
         Expect(i::Token::RPAREN, CHECK_OK);
 
         ParseStatement(CHECK_OK);
         return Statement::Default();
       }
     } else {
       ParseExpression(false, CHECK_OK);
       if (peek() == i::Token::IN) {
@@ skipping 1095 matching lines @@
       backing_store_.Add(static_cast<byte>((ascii_length >> 14) | 0x80u));
     }
     backing_store_.Add(static_cast<byte>((ascii_length >> 7) | 0x80u));
   }
   backing_store_.Add(static_cast<byte>(ascii_length & 0x7f));
 
   backing_store_.AddBlock(bytes);
   return backing_store_.EndSequence().start();
 }
 } }  // v8::preparser