Fix bug with re-scoping arrow function parameter initializers

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 "src/accessors.h"
 #include "src/ast/scopeinfo.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
@@ skipping 542 matching lines @@
                                        name,
                                        TEMPORARY,
                                        Variable::NORMAL,
                                        kCreatedInitialized);
   scope->AddTemporary(var);
   return var;
 }
 
 int Scope::RemoveTemporary(Variable* var) {
   DCHECK_NOT_NULL(var);
+  // Temporaries are only placed in ClosureScopes.
+  DCHECK_EQ(ClosureScope(), this);
+  DCHECK_EQ(var->scope()->ClosureScope(), var->scope());
+  // If the temporary is not here, return quickly.
+  if (var->scope() != this) return -1;
   // Most likely (always?) any temporary variable we want to remove
   // was just added before, so we search backwards.
   for (int i = temps_.length(); i-- > 0;) {
     if (temps_[i] == var) {
       // Don't shrink temps_, as callers of this method expect
       // the returned indices to be unique per-scope.
       temps_[i] = nullptr;
       return i;
     }
   }
@@ skipping 944 matching lines @@
       function_ != NULL && function_->proxy()->var()->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS - num_global_slots() -
          (is_function_var_in_context ? 1 : 0);
 }
 
 
 int Scope::ContextGlobalCount() const { return num_global_slots(); }
 
 }  // namespace internal
 }  // namespace v8