[parser] Enforce module-specific identifier restriction

src/parsing/preparser.cc

Index: src/parsing/preparser.cc
diff --git a/src/parsing/preparser.cc b/src/parsing/preparser.cc
index d335c8bdcd29433337d1173c9e17b3a1e116a999..b48b947e80b508e532bdb547c44e51cf58cc4192 100644
--- a/src/parsing/preparser.cc
+++ b/src/parsing/preparser.cc
@@ -38,8 +38,10 @@ void PreParserTraits::ReportMessageAt(int start_pos, int end_pos,
 
 
 PreParserIdentifier PreParserTraits::GetSymbol(Scanner* scanner) {
-  if (scanner->current_token() == Token::FUTURE_RESERVED_WORD) {
-    return PreParserIdentifier::FutureReserved();
+  if (scanner->current_token() == Token::ENUM) {
+    return PreParserIdentifier::Enum();
+  } else if (scanner->current_token() == Token::AWAIT) {
+    return PreParserIdentifier::Await();
   } else if (scanner->current_token() ==
              Token::FUTURE_STRICT_RESERVED_WORD) {
     return PreParserIdentifier::FutureStrictReserved();
@@ -694,7 +696,6 @@ PreParser::Statement PreParser::ParseExpressionOrLabelledStatement(bool* ok) {
   if (starts_with_identifier && expr.IsIdentifier() && peek() == Token::COLON) {
     // Expression is a single identifier, and not, e.g., a parenthesized
     // identifier.
-    DCHECK(!expr.AsIdentifier().IsFutureReserved());

[mike3, 2016/02/23 19:29:44]

I'm not convinced that removing this check outright (instead of updating it) is
valid, but I haven't been able to think of a test that proves otherwise.

[adamk, 2016/02/23 22:37:15]

"DCHECK" is the V8 equivalent of "assert": it's not meant to be something that a
known test case could be written for, it's stating assumptions about invariants
at this part of the code. So I'd prefer it be updated rather than removed.

[mike3, 2016/02/24 16:20:54]

Acknowledged.

     DCHECK(is_sloppy(language_mode()) ||
            !IsFutureStrictReserved(expr.AsIdentifier()));
     Consume(Token::COLON);