RFC: Resolution based tree-shaking.

dart/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 246 matching lines @@
   Send asSend() => this;
 
   accept(Visitor visitor) => visitor.visitSend(this);
 
   visitChildren(Visitor visitor) {
     if (receiver !== null) receiver.accept(visitor);
     if (selector !== null) selector.accept(visitor);
     if (argumentsNode !== null) argumentsNode.accept(visitor);
   }
 
-  int argumentCount() => argumentsNode.length();
+  int argumentCount() => (argumentsNode === null) ? -1 : argumentsNode.length();
 
   bool get isSuperCall() {
     return receiver !== null &&
            receiver.asIdentifier() !== null &&
            receiver.asIdentifier().isSuper();
   }
   bool get isOperator() => selector is Operator;
   bool get isPropertyAccess() => argumentsNode === null;
   bool get isFunctionObjectInvocation() => selector === null;
   bool get isPrefix() => argumentsNode is Prefix;
@@ skipping 1431 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);
 }