Mark the local for this as used if a constructor call needs type variables.

lib/compiler/implementation/tree/nodes.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 interface Visitor<R> {
   R visitBlock(Block node);
   R visitBreakStatement(BreakStatement node);
   R visitCascade(Cascade node);
   R visitCascadeReceiver(CascadeReceiver node);
   R visitCaseMatch(CaseMatch node);
@@ skipping 287 matching lines @@
       return argumentsNode.getEndToken();
     }
     if (selector !== null) return selector.getEndToken();
     return receiver.getBeginToken();
   }
 
   Send copyWithReceiver(Node newReceiver) {
     assert(receiver === null);
     return new Send(newReceiver, selector, argumentsNode);
   }
+
+  /**
+   * Returns the type annotation of a connstructor call in an object
+   * instantiation.
+   */
+  TypeAnnotation getTypeAnnotation() {
+    if (selector is TypeAnnotation) {
+      return selector;
+    } else if (selector is Send) {
+      Send selectorSend = selector;
+      if (selectorSend.receiver is TypeAnnotation) {
+        return selectorSend.receiver;
+      }
+    }
+    return null;
+  }
 }
 
 class Postfix extends NodeList {
   Postfix() : super(nodes: const EmptyLink<Node>());
   Postfix.singleton(Node argument) : super.singleton(argument);
 }
 
 class Prefix extends NodeList {
   Prefix() : super(nodes: const EmptyLink<Node>());
   Prefix.singleton(Node argument) : super.singleton(argument);
@@ skipping 1433 matching lines @@
  * argument).
  *
  * TODO(ahe): This method is controversial, the team needs to discuss
  * if top-level methods are acceptable and what naming conventions to
  * use.
  */
 initializerDo(Node node, f(Node node)) {
   SendSet send = node.asSendSet();
   if (send !== null) return f(send.arguments.head);
 }