[strong] Deprecate for-in

src/preparser.cc

Index: src/preparser.cc
diff --git a/src/preparser.cc b/src/preparser.cc
index 00332ada0985fdb644f006195d5ffd5f9fdbd30f..94ac6b4844ebf3916bfcfa8645efcdb5a32f8857 100644
--- a/src/preparser.cc
+++ b/src/preparser.cc
@@ -715,9 +715,14 @@ PreParser::Statement PreParser::ParseWhileStatement(bool* ok) {
 }
 
 
-bool PreParser::CheckInOrOf(bool accept_OF) {
-  if (Check(Token::IN) ||
-      (accept_OF && CheckContextualKeyword(CStrVector("of")))) {
+bool PreParser::CheckInOrOf(bool accept_OF, bool* ok) {
+  if (Check(Token::IN)) {
+    if (is_strong(language_mode())) {
+      ReportMessageAt(scanner()->location(), "strong_for_in");
+      *ok = false;
+    }
+    return true;
+  } else if (accept_OF && CheckContextualKeyword(CStrVector("of"))) {
     return true;
   }
   return false;
@@ -743,22 +748,24 @@ PreParser::Statement PreParser::ParseForStatement(bool* ok) {
       bool has_initializers = decl_props == kHasInitializers;
       bool accept_IN = decl_count == 1 && !(is_lexical && has_initializers);
       bool accept_OF = !has_initializers;
-      if (accept_IN && CheckInOrOf(accept_OF)) {
-        ParseExpression(true, CHECK_OK);
-        Expect(Token::RPAREN, CHECK_OK);
-
-        ParseSubStatement(CHECK_OK);
+      if (accept_IN && CheckInOrOf(accept_OF, ok)) {
+        if (*ok) {

[marja, 2015/02/19 12:34:22]

Nit: I'd write this the same style as Parser, so,

if (!*ok) early return_;
go_on();

... just to keep the logic as unified as possible. It's just a tiny thing but
Parser / PreParser are full of these unnecessary "let's inverse the condition
and write the blocks in a different order" things which accumulate and make the
eventual unification more tedious.

[rossberg, 2015/02/19 13:23:05]

Done.

+          ParseExpression(true, CHECK_OK);
+          Expect(Token::RPAREN, CHECK_OK);
+          ParseSubStatement(CHECK_OK);
+        }
         return Statement::Default();
       }
     } else {
       Expression lhs = ParseExpression(false, CHECK_OK);
       is_let_identifier_expression =
           lhs.IsIdentifier() && lhs.AsIdentifier().IsLet();
-      if (CheckInOrOf(lhs.IsIdentifier())) {
-        ParseExpression(true, CHECK_OK);
-        Expect(Token::RPAREN, CHECK_OK);
-
-        ParseSubStatement(CHECK_OK);
+      if (CheckInOrOf(lhs.IsIdentifier(), ok)) {
+        if (*ok) {
+          ParseExpression(true, CHECK_OK);
+          Expect(Token::RPAREN, CHECK_OK);
+          ParseSubStatement(CHECK_OK);
+        }
         return Statement::Default();
       }
     }