harmony-scoping: Allow 'const' iteration variables in strict mode.

src/preparser.cc

Index: src/preparser.cc
diff --git a/src/preparser.cc b/src/preparser.cc
index 987900a20d5844ebfef3e17d93fcd4c43f9503ea..7b781397c9ff0268b23e7eee8a36085f3a8c8a07 100644
--- a/src/preparser.cc
+++ b/src/preparser.cc
@@ -409,6 +409,7 @@ PreParser::Statement PreParser::ParseVariableDeclarations(
   // ConstBinding ::
   //   BindingPattern '=' AssignmentExpression
   bool require_initializer = false;
+  bool is_strict_const = false;
   if (peek() == Token::VAR) {
     Consume(Token::VAR);
   } else if (peek() == Token::CONST) {
@@ -430,7 +431,8 @@ PreParser::Statement PreParser::ParseVariableDeclarations(
           *ok = false;
           return Statement::Default();
         }
-        require_initializer = true;
+        is_strict_const = true;
+        require_initializer = var_context != kForStatement;
       } else {
         Scanner::Location location = scanner()->peek_location();
         ReportMessageAt(location, "strict_const");
@@ -460,7 +462,8 @@ PreParser::Statement PreParser::ParseVariableDeclarations(
     if (nvars > 0) Consume(Token::COMMA);
     ParseIdentifier(kDontAllowEvalOrArguments, CHECK_OK);
     nvars++;
-    if (peek() == Token::ASSIGN || require_initializer) {
+    if (peek() == Token::ASSIGN || require_initializer ||
+        (is_strict_const && peek() == Token::COMMA)) {

[rossberg, 2014/10/23 09:44:54]

I don't understand this condition. If it is true, you always will produce a
syntax error on the next line. Is that intentional? If so, perhaps put in an
explanatory comment (or refactor).

[Dmitry Lomov (no reviews), 2014/10/23 10:33:34]

Yes, intentional. Comment added.

       Expect(Token::ASSIGN, CHECK_OK);
       ParseAssignmentExpression(var_context != kForStatement, CHECK_OK);
       if (decl_props != NULL) *decl_props = kHasInitializers;
@@ -678,13 +681,16 @@ PreParser::Statement PreParser::ParseForStatement(bool* ok) {
   if (peek() != Token::SEMICOLON) {
     if (peek() == Token::VAR || peek() == Token::CONST ||
         (peek() == Token::LET && strict_mode() == STRICT)) {
-      bool is_let = peek() == Token::LET;
+      bool is_let_or_strict_const =

[rossberg, 2014/10/23 09:44:54]

Nit: how about naming this 'is_lexical'?

[Dmitry Lomov (no reviews), 2014/10/23 10:33:34]

Done.

+          peek() == Token::LET ||
+          (peek() == Token::CONST && strict_mode() == STRICT);
       int decl_count;
       VariableDeclarationProperties decl_props = kHasNoInitializers;
       ParseVariableDeclarations(
           kForStatement, &decl_props, &decl_count, CHECK_OK);
       bool has_initializers = decl_props == kHasInitializers;
-      bool accept_IN = decl_count == 1 && !(is_let && has_initializers);
+      bool accept_IN =
+          decl_count == 1 && !(is_let_or_strict_const && has_initializers);
       bool accept_OF = !has_initializers;
       if (accept_IN && CheckInOrOf(accept_OF)) {
         ParseExpression(true, CHECK_OK);