Reland of write scopes of non-simple default arguments

src/parsing/parameter-initializer-rewriter.cc

 // Copyright 2015 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/parsing/parameter-initializer-rewriter.h"
 
 #include <algorithm>
 #include <utility>
 #include <vector>
 
@@ skipping 72 matching lines @@
     // the class scope on their scope chain.
     DCHECK(prop->value()->IsFunctionLiteral());
   }
 }
 
 
 void Rewriter::VisitVariableProxy(VariableProxy* proxy) {
   if (proxy->is_resolved()) {
     Variable* var = proxy->var();
     if (var->mode() != TEMPORARY) return;
+    // For rewriting inside the same ClosureScope (e.g., putting default
+    // parameter values in their own inner scope in certain cases), refrain
+    // from invalidly moving temporaries to a block scope.
+    if (var->scope()->ClosureScope() == new_scope_->ClosureScope()) return;
     int index = old_scope_->RemoveTemporary(var);
     if (index >= 0) {
       temps_.push_back(std::make_pair(var, index));
     }
   } else if (old_scope_->RemoveUnresolved(proxy)) {
     new_scope_->AddUnresolved(proxy);
   }
 }
 
 
@@ skipping 23 matching lines @@
 void RewriteParameterInitializerScope(uintptr_t stack_limit,
                                       Expression* initializer, Scope* old_scope,
                                       Scope* new_scope) {
   Rewriter rewriter(stack_limit, initializer, old_scope, new_scope);
   rewriter.Run();
 }
 
 
 }  // namespace internal
 }  // namespace v8