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

src/ast/scopes.cc

 // Copyright 2012 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.
 
 #include "src/ast/scopes.h"
 
 #include <set>
 
 #include "src/accessors.h"
 #include "src/ast/ast.h"
@@ skipping 618 matching lines @@
   function_ =
       new (zone()) Variable(this, name, CONST, kind, kCreatedInitialized);
   if (calls_sloppy_eval()) {
     NonLocal(name, DYNAMIC);
   } else {
     variables_.Add(zone(), function_);
   }
   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());
 
   if (variables_.occupancy() > 0 ||
       (is_declaration_scope() && calls_sloppy_eval())) {
     return this;
   }
 
   // Remove this scope from outer scope.
   outer_scope()->RemoveInnerScope(this);
@@ skipping 1378 matching lines @@
   Variable* function =
       is_function_scope() ? AsDeclarationScope()->function_var() : nullptr;
   bool is_function_var_in_context =
       function != nullptr && function->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
          (is_function_var_in_context ? 1 : 0);
 }
 
 }  // namespace internal
 }  // namespace v8