Support optional function expression parameters in dart2js.

sdk/lib/_internal/compiler/implementation/resolution/members.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.
 
 part of resolution;
 
 abstract class TreeElements {
   Element get currentElement;
   Set<Node> get superUses;
 
@@ skipping 3560 matching lines @@
           ElementKind.VARIABLE_LIST, enclosingElement);
       element = new FieldParameterElementX(name, fieldElement, variables, node);
     }
     return element;
   }
 
   Element visitSendSet(SendSet node) {
     Element element;
     if (node.receiver != null) {
       element = visitSend(node);
-    } else if (node.selector.asIdentifier() != null) {
+    } else if (node.selector.asIdentifier() != null ||
+               node.selector.asFunctionExpression() != null) {
       Element variables = new VariableListElementX.node(currentDefinitions,
           ElementKind.VARIABLE_LIST, enclosingElement);
-      element = new VariableElementX(node.selector.asIdentifier().source,
-          variables, ElementKind.PARAMETER, node);
+      SourceString source = node.selector.asIdentifier() != null ?
+          node.selector.asIdentifier().source :
+          node.selector.asFunctionExpression().name.asIdentifier().source;
+      element = new VariableElementX(source, variables,
+          ElementKind.PARAMETER, node);
     }
     // Visit the value. The compile time constant handler will
     // make sure it's a compile time constant.
     resolveExpression(node.arguments.head);
     return element;
   }
 
   Element visitFunctionExpression(FunctionExpression node) {
     // This is a function typed parameter.
     // TODO(ahe): Resolve the function type.
@@ skipping 246 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }