[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 {
+  if (!is_block_scope() || is_declaration_scope()) return false;  // Shortcut.

[Toon Verwaest, 2016/11/23 12:20:45]

if (is_declaration_scope()) return false;
DCHECK(is_block_scope());

[neis, 2016/11/23 15:52:38]

This DCHECK is failing, for instance in the following nonsense code:

for(let y in [5,6,7,8]) with({}) { let([, [x4]] = ([new (undefined)(-1)]), [] =
[11,12,13,14].map) ((function(){throw StopIteration;})()); } 

where it's a with scope.

+
+  Scope* parent = outer_scope();
+  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;
+  }
+
+  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