[es6] implement destructuring assignment

src/crankshaft/typing.cc

Index: src/crankshaft/typing.cc
diff --git a/src/crankshaft/typing.cc b/src/crankshaft/typing.cc
index cf255cbf49b1203dff1c716516cd5132a88307c4..df50f81167c8ad2476e900ce2b049318959c3e12 100644
--- a/src/crankshaft/typing.cc
+++ b/src/crankshaft/typing.cc
@@ -770,6 +770,12 @@ void AstTyper::VisitSuperPropertyReference(SuperPropertyReference* expr) {}
 void AstTyper::VisitSuperCallReference(SuperCallReference* expr) {}
 
 
+void AstTyper::VisitRewritableAssignmentExpression(
+    RewritableAssignmentExpression* expr) {
+  Visit(expr->expression());
+}
+
+
 void AstTyper::VisitDeclarations(ZoneList<Declaration*>* decls) {
   for (int i = 0; i < decls->length(); ++i) {
     Declaration* decl = decls->at(i);