Make sure that names of temporaries do not clash with real variables.

src/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
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@@ skipping 2824 matching lines @@
         //
         //   <let x' be a temporary variable>
         //   for (x' in e) {
         //     let x;
         //     x = x';
         //     b;
         //   }
 
         // TODO(keuchel): Move the temporary variable to the block scope, after
         // implementing stack allocated block scoped variables.
-        Variable* temp = top_scope_->DeclarationScope()->NewTemporary(name);
+        Factory* heap_factory = isolate()->factory();
+        Handle<String> dot =
+            heap_factory->NewStringFromAscii(CStrVector(".for."));

[Michael Starzinger, 2012/10/05 12:31:38]

You could move this symbol into the root-set by adding it to SYMBOL_LIST, call
it e.g. dot_for_symbol and then access it through factory->dot_for_symbol().

Also does the name really need to be different for every temporary, or could we
use the one symbol for all temporaries?

[rossberg, 2012/10/05 12:47:04]

Done.
There can be several loop variables in the same scope, so they should be
distinguishable.

+        Handle<String> tempstr = heap_factory->NewConsString(dot, name);
+        Handle<String> tempname = heap_factory->LookupSymbol(tempstr);
+        Variable* temp = top_scope_->DeclarationScope()->NewTemporary(tempname);
         VariableProxy* temp_proxy = factory()->NewVariableProxy(temp);
         ForInStatement* loop = factory()->NewForInStatement(labels);
         Target target(&this->target_stack_, loop);
 
         // The expression does not see the loop variable.
         Expect(Token::IN, CHECK_OK);
         top_scope_ = saved_scope;
         Expression* enumerable = ParseExpression(true, CHECK_OK);
         top_scope_ = for_scope;
         Expect(Token::RPAREN, CHECK_OK);
@@ skipping 3120 matching lines @@
       ASSERT(info->isolate()->has_pending_exception());
     } else {
       result = parser.ParseProgram();
     }
   }
   info->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal