Simplify implementation of assignment-to-const checks

src/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2988 matching lines @@
   if (!Token::IsAssignmentOp(peek())) {
     if (fni_ != NULL) fni_->Leave();
     // Parsed conditional expression only (no assignment).
     return expression;
   }
 
   // Signal a reference error if the expression is an invalid left-hand
   // side expression.  We could report this as a syntax error here but
   // for compatibility with JSC we choose to report the error at
   // runtime.
+  // TODO(ES5): Should change parsing for spec conformance.
   if (expression == NULL || !expression->IsValidLeftHandSide()) {
     Handle<String> type =
         isolate()->factory()->invalid_lhs_in_assignment_symbol();
     expression = NewThrowReferenceError(type);
   }
 
   if (!top_scope_->is_classic_mode()) {
     // Assignment to eval or arguments is disallowed in strict mode.
     CheckStrictModeLValue(expression, "strict_lhs_assignment", CHECK_OK);
   }
@@ skipping 2909 matching lines @@
       ASSERT(info->isolate()->has_pending_exception());
     } else {
       result = parser.ParseProgram();
     }
   }
   info->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal