Fixed dart2js compile errors in ir_builder and ir_nodes.

sdk/lib/_internal/compiler/implementation/ir/ir_builder.dart

Index: sdk/lib/_internal/compiler/implementation/ir/ir_builder.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ir/ir_builder.dart b/sdk/lib/_internal/compiler/implementation/ir/ir_builder.dart
index 137703ef53c795305f2edc6b7069efc88e48b56b..e80aa26c07ceefceb645a8e015afceec421ea788 100644
--- a/sdk/lib/_internal/compiler/implementation/ir/ir_builder.dart
+++ b/sdk/lib/_internal/compiler/implementation/ir/ir_builder.dart
@@ -1180,7 +1180,9 @@ class IrBuilder extends ResolvedVisitor<ir.Primitive> {
         // - Assignment to final variable (will not be resolved)
         return giveup(node, 'SendSet: non-local, non-static, but no receiver');
       } else {
-        if (element != null && Elements.isUnresolved(element)) return giveup();
+        if (element != null && Elements.isUnresolved(element)) {
+          return giveup(node);
+        }
 
         // Setter or index-setter invocation
         assert(node.receiver != null);