[es6] implement destructuring assignment

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index 92afa4fcc99c49f5cb8d43e74803ac99ec970366..54f435d9dca52db09026a96c24bfa7101269080b 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -1697,6 +1697,11 @@ void AstGraphBuilder::VisitRegExpLiteral(RegExpLiteral* expr) {
 }
 
 
+void AstGraphBuilder::VisitAssignmentPattern(AssignmentPattern* expr) {
+  Visit(expr->expression());
+}
+
+
 void AstGraphBuilder::VisitObjectLiteral(ObjectLiteral* expr) {
   Node* closure = GetFunctionClosure();
 
@@ -2056,6 +2061,10 @@ void AstGraphBuilder::VisitForInAssignment(Expression* expr, Node* value,
 
 
 void AstGraphBuilder::VisitAssignment(Assignment* expr) {
+  if (expr->target()->IsAssignmentPattern()) {
+    DCHECK(expr->target()->AsAssignmentPattern()->is_rewritten());
+    return Visit(expr->target()->AsAssignmentPattern()->expression());
+  }
   DCHECK(expr->target()->IsValidReferenceExpressionOrThis());
 
   // Left-hand side can only be a property, a global or a variable slot.