Add flag to make await and yield keywords

runtime/vm/parser.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/parser.h"
 #include "vm/flags.h"
 
 #ifndef DART_PRECOMPILED
 
 #include "lib/invocation_mirror.h"
@@ skipping 34 matching lines @@
     "Disable to make importing dart:mirrors an error.");
 DEFINE_FLAG(bool, load_deferred_eagerly, false,
     "Load deferred libraries eagerly.");
 DEFINE_FLAG(bool, trace_parser, false, "Trace parser operations.");
 DEFINE_FLAG(bool, warn_mixin_typedef, true, "Warning on legacy mixin typedef.");
 DEFINE_FLAG(bool, link_natives_lazily, false, "Link native calls lazily");
 DEFINE_FLAG(bool, conditional_directives, false,
     "Enable conditional directives");
 DEFINE_FLAG(bool, warn_super, false,
     "Warning if super initializer not last in initializer list.");
+DEFINE_FLAG(bool, await_is_keyword, false,
+    "await and yield are treated as proper keywords in synchronous code.");
 
 DECLARE_FLAG(bool, lazy_dispatchers);
 DECLARE_FLAG(bool, load_deferred_eagerly);
 DECLARE_FLAG(bool, profile_vm);
 DECLARE_FLAG(bool, throw_on_javascript_int_overflow);
 DECLARE_FLAG(bool, warn_on_javascript_compatibility);
 
 // Quick access to the current thread, isolate and zone.
 #define T (thread())
 #define I (isolate())
@@ skipping 10108 matching lines @@
   if (!IsIdentifier()) {
     ReportError("%s", msg);
   }
   String* ident = CurrentLiteral();
   ConsumeToken();
   return ident;
 }
 
 
 bool Parser::IsAwaitKeyword() {
-  return await_is_keyword_ && IsSymbol(Symbols::Await());
+  return (FLAG_await_is_keyword || await_is_keyword_) &&
+      IsSymbol(Symbols::Await());
 }
 
 
 bool Parser::IsYieldKeyword() {
-  return await_is_keyword_ && IsSymbol(Symbols::YieldKw());
+  return (FLAG_await_is_keyword || await_is_keyword_) &&
+      IsSymbol(Symbols::YieldKw());
 }
 
 
 static bool IsIncrementOperator(Token::Kind token) {
   return token == Token::kINCR || token == Token::kDECR;
 }
 
 
 static bool IsPrefixOperator(Token::Kind token) {
   return (token == Token::kSUB) ||
@@ skipping 4187 matching lines @@
     const ArgumentListNode& function_args,
     const LocalVariable* temp_for_last_arg,
     bool is_super_invocation) {
   UNREACHABLE();
   return NULL;
 }
 
 }  // namespace dart
 
 #endif  // DART_PRECOMPILED