[parser] Rewritable expressions should not be valid variable references

src/ast/ast.cc

Index: src/ast/ast.cc
diff --git a/src/ast/ast.cc b/src/ast/ast.cc
index 1554a5e0b9761856b86ba99263743dc96c6627db..8529b5b445133571f9ceeb7c042f52f641d731df 100644
--- a/src/ast/ast.cc
+++ b/src/ast/ast.cc
@@ -125,6 +125,10 @@ bool Expression::ToBooleanIsFalse() const {
 }
 
 bool Expression::IsValidReferenceExpression() const {
+  // We don't want expressions wrapped inside RewritableExpression to be
+  // considered as valid reference expressions, as they will be rewritten
+  // to something (most probably involving a do expression).
+  if (IsRewritableExpression()) return false;

[Michael Starzinger, 2016/07/18 13:08:04]

I am confused, how can the below predicate return true for a
RewritableExpression?

[Michael Starzinger, 2016/07/18 13:10:13]

Ah, now I see, the IsFoo predicates actually special case for
RewritableExpression ... oh god ...

[nickie, 2016/07/18 13:13:18]

That's the point.  They never should be.  They never were before CL 2126233002. 
The default for Expression was false:

https://codereview.chromium.org/2126233002/diff/180001/src/ast/ast.h#oldcode300

and that CL changed it:

https://codereview.chromium.org/2126233002/diff/180001/src/ast/ast.cc#newcode136

   return IsProperty() ||
          (IsVariableProxy() && AsVariableProxy()->IsValidReferenceExpression());
 }