[es6] Fix scoping for default parameters in arrow functions

src/parser.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/parser.h"
 
 #include "src/api.h"
 #include "src/ast.h"
 #include "src/ast-literal-reindexer.h"
 #include "src/bailout-reason.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
 #include "src/char-predicates-inl.h"
 #include "src/codegen.h"
 #include "src/compiler.h"
 #include "src/messages.h"
+#include "src/parameter-initializer-rewriter.h"
 #include "src/preparser.h"
 #include "src/rewriter.h"
 #include "src/runtime/runtime.h"
 #include "src/scanner-character-streams.h"
 #include "src/scopeinfo.h"
 #include "src/string-stream.h"
 
 namespace v8 {
 namespace internal {
 
@@ skipping 4015 matching lines @@
     // parse-time side-effect for parameters that are single-names (not
     // patterns; for patterns that happens uniformly in
     // PatternRewriter::VisitVariableProxy).
     parser_->scope_->RemoveUnresolved(expr->AsVariableProxy());
   } else if (expr->IsAssignment()) {
     Assignment* assignment = expr->AsAssignment();
     DCHECK(parser_->allow_harmony_default_parameters());
     DCHECK(!assignment->is_compound());
     initializer = assignment->value();
     expr = assignment->target();
+
+    // TODO(adamk): Only call this if necessary.
+    RewriteParameterInitializerScope(parser_->stack_limit(), initializer,
+                                     parser_->scope_, parameters->scope);
   }
 
   AddFormalParameter(parameters, expr, initializer, is_rest);
 }
 
 
 DoExpression* Parser::ParseDoExpression(bool* ok) {
   // AssignmentExpression ::
   //     do '{' StatementList '}'
   int pos = peek_position();
@@ skipping 2320 matching lines @@
 
 Expression* Parser::SpreadCallNew(Expression* function,
                                   ZoneList<v8::internal::Expression*>* args,
                                   int pos) {
   args->InsertAt(0, function, zone());
 
   return factory()->NewCallRuntime(Context::REFLECT_CONSTRUCT_INDEX, args, pos);
 }
 }  // namespace internal
 }  // namespace v8