[parser] Fix scopes in rewriting of for-of and destructuring assignments.

src/ast/scopes.cc

Index: src/ast/scopes.cc
diff --git a/src/ast/scopes.cc b/src/ast/scopes.cc
index c150336668545eb1a8bf78b3af3823f70bb476c1..21d67bcf5b24288f9f8dcb12f1200a5af67989c6 100644
--- a/src/ast/scopes.cc
+++ b/src/ast/scopes.cc
@@ -636,6 +636,22 @@ Variable* DeclarationScope::DeclareFunctionVar(const AstRawString* name) {
   return function_;
 }
 
+bool Scope::HasBeenRemoved() const {
+  Scope* parent = outer_scope();

[Toon Verwaest, 2016/11/22 08:30:18]

if (is_declaration_scope()) return false; ?

[Dan Ehrenberg, 2016/11/22 16:07:00]

Or, that could be an assertion before the return true, that it's not a
declaration scope

[Toon Verwaest, 2016/11/22 16:18:37]

That's what I was originally thinking of suggesting; but we'd walk the chain for
no reason which is slower :)

[neis, 2016/11/23 12:51:08]

Done.

+  if (parent == nullptr) {
+    DCHECK(is_script_scope());
+    return false;
+  }
+
+  Scope* sibling = parent->inner_scope();
+  for (; sibling != nullptr; sibling = sibling->sibling()) {
+    if (sibling == this) return false;
+  }

[Dan Ehrenberg, 2016/11/22 16:07:00]

This is asymptotically a bit unfortunate. Is there another way we could mark
already-removed scopes? This can wait for a follow-on patch.

[Toon Verwaest, 2016/11/22 16:19:47]

Yeah that's a good suggestion though. We can just have a single bit on Scope.

+
+  DCHECK_NULL(inner_scope_);
+  return true;
+}
+
 Scope* Scope::FinalizeBlockScope() {
   DCHECK(is_block_scope());