closure calls (just the invocation part).

frog/leg/resolver.dart

 // Copyright (c) 2011, 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.
 
 class TreeElements {
   Map<Node, Element> map;
   TreeElements() : map = new LinkedHashMap<Node, Element>();
   operator []=(Node node, Element element) => map[node] = element;
   operator [](Node node) => map[node];
 }
@@ skipping 299 matching lines @@
 
   static bool isLogicalOperator(Identifier op) {
     String str = op.source.stringValue;
     return (str === '&&' || str == '||' || str == '!');
   }
 
   Element resolveSend(Send node) {
     Element receiver = visit(node.receiver);
     visit(node.argumentsNode);
 
-    Identifier selector = node.selector;
+    Identifier selector = node.selector.asIdentifier();
+    if (selector === null) {
+      // We are calling a closure returned from an expression.
+      assert(node.selector.asExpression() !== null);
+      assert(receiver === null);
+      visit(node.selector);
+      return null;
+    }
+
     SourceString name = selector.source;
     // No need to assign an element for a logical operation.
     if (isLogicalOperator(selector)) return null;
 
     Element target = null;
     if (node.isOperator) {
       return null;
     } else if (node.receiver === null) {
       target = lookup(node, name);
       if (target == null && !enclosingElement.isInstanceMember()) {
@@ skipping 374 matching lines @@
 class TopScope extends Scope {
   Universe universe;
 
   TopScope(Universe this.universe) : super(null, null);
   Element lookup(SourceString name) => universe.find(name);
 
   Element add(Element element) {
     throw "Cannot add an element in the top scope";
   }
 }