[es6] implement optional parameters via desugaring (with scoping)

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index e71314f9c1af9558e6e249e16cdaab7dca870397..d5dc3d11f5848515343d0fc78ebf0dabb1bc5414 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -717,7 +717,8 @@ enum ScopeType {
   CATCH_SCOPE,     // The scope introduced by catch.
   BLOCK_SCOPE,     // The scope introduced by a new block.
   WITH_SCOPE,      // The scope introduced by with.
-  ARROW_SCOPE      // The top-level scope for an arrow function literal.
+  ARROW_SCOPE,     // The top-level scope for an arrow function literal.
+  PARAMETER_SCOPE  // The scope for parameter initialization

[Dmitry Lomov (no reviews), 2015/04/28 08:57:09]

Do we really need this extra scope type? Why cannot it just be a BLOCK_SCOPE?

Otherwise, you need to comb the code for references to BLOCK_SCOPE and make sure
that PARAMETER_SCOPE is handled correctly.

 };
 
 // The mips architecture prior to revision 5 has inverted encoding for sNaN.