[es6] conditionally ignore TDZ semantics for formals

src/pattern-rewriter.cc

Index: src/pattern-rewriter.cc
diff --git a/src/pattern-rewriter.cc b/src/pattern-rewriter.cc
index f7e5b434664ce5905effdbee891e44859ae77aea..d90baf9967b6ea29bb9d0449159d3d01b5ddcfd4 100644
--- a/src/pattern-rewriter.cc
+++ b/src/pattern-rewriter.cc
@@ -53,9 +53,11 @@ void Parser::PatternRewriter::VisitVariableProxy(VariableProxy* pattern) {
   Declaration* declaration = factory()->NewVariableDeclaration(
       proxy, descriptor_->mode, descriptor_->scope,
       descriptor_->declaration_pos);
-  Variable* var = parser->Declare(declaration, descriptor_->declaration_kind,
-                                  descriptor_->mode != VAR, ok_,
-                                  descriptor_->hoist_scope);
+  Variable* var = parser->Declare(
+      declaration, descriptor_->declaration_kind,
+      descriptor_->declaration_kind == DeclarationDescriptor::PARAMETER ||
+          descriptor_->mode != VAR,
+      ok_, descriptor_->hoist_scope);
   if (!*ok_) return;
   DCHECK_NOT_NULL(var);
   DCHECK(!proxy->is_resolved() || proxy->var() == var);