harmony-scoping: make assignment to 'const' a late error.

src/variables.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_VARIABLES_H_
 #define V8_VARIABLES_H_
 
 #include "src/ast-value-factory.h"
 #include "src/interface.h"
 #include "src/zone.h"
@@ skipping 117 matching lines @@
   }
   Interface* interface() const { return interface_; }
 
   void AllocateTo(Location location, int index) {
     location_ = location;
     index_ = index;
   }
 
   static int CompareIndex(Variable* const* v, Variable* const* w);
 
+  // Shall an error be thrown if assignment with 'op' operation is perfomed
+  // on this variable in given language mode?
+  bool IsSignallingAssignmentToConst(Token::Value op,
+                                     StrictMode strict_mode) const {
+    if (mode() == CONST) return op != Token::INIT_CONST;

[rossberg, 2014/11/25 15:23:36]

Hm, wouldn't it be easier and more accurate to implement this as follows:

  if (strict_mode = SLOPPY) return false;
  if (op == Token::INIT_CONST || op == Token::INIT_CONST_LEGACY) return false;
  return mode() == CONST || mode() == CONST_LEGACY;

[Dmitry Lomov (no reviews), 2014/11/25 15:51:01]

Hmm, I like my version better since it puts the variable mode first.
I did a hybrid of the two which I think is more readable

[rossberg, 2014/11/25 16:25:02]

Looks good.

+
+    if (mode() == CONST_LEGACY) {
+      return strict_mode == STRICT && op != Token::INIT_CONST_LEGACY &&
+             op != Token::INIT_CONST;

[rossberg, 2014/11/25 15:23:36]

Can this even occur when mode is CONST_LEGACY?

[Dmitry Lomov (no reviews), 2014/11/25 15:51:01]

No, done

+    }
+
+    return false;
+  }
+
  private:
   Scope* scope_;
   const AstRawString* name_;
   VariableMode mode_;
   Kind kind_;
   Location location_;
   int index_;
   int initializer_position_;
 
   // If this field is set, this variable references the stored locally bound
@@ skipping 12 matching lines @@
   MaybeAssignedFlag maybe_assigned_;
 
   // Module type info.
   Interface* interface_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_VARIABLES_H_