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

src/variables.h

Index: src/variables.h
diff --git a/src/variables.h b/src/variables.h
index 93bfb4a1816aeb3fb9f370c847ace86da6f2d6b3..aa9c118c3e81961a3299a8dfc928583479a1e28f 100644
--- a/src/variables.h
+++ b/src/variables.h
@@ -135,6 +135,20 @@ class Variable: public ZoneObject {
 
   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_;