Use `Function` as function type syntax.

pkg/compiler/lib/src/kernel/kernel.dart

 // Copyright (c) 2016, 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.md file.
 
 import 'dart:async';
 import 'dart:collection' show Queue;
 
 import 'package:kernel/ast.dart' as ir;
 import 'package:kernel/checks.dart' show CheckParentPointers;
 
@@ skipping 17 matching lines @@
         LibraryElement,
         LocalFunctionElement,
         MetadataAnnotation,
         MixinApplicationElement,
         TypeVariableElement;
 import '../elements/modelx.dart' show ErroneousFieldElementX;
 import '../tree/tree.dart' show FunctionExpression, Node;
 import 'constant_visitor.dart';
 import 'kernel_visitor.dart' show IrFunction, KernelVisitor;
 
-typedef void WorkAction();
-
 class WorkItem {
   final Element element;
-  final WorkAction action;
+  final void Function() action;
 
   WorkItem(this.element, this.action);
 }
 
 class Kernel {
   final Compiler compiler;
 
   final Map<LibraryElement, ir.Library> libraries =
       <LibraryElement, ir.Library>{};
 
@@ skipping 20 matching lines @@
 
   final Map<ir.Node, Element> nodeToElement = <ir.Node, Element>{};
   final Map<ir.Node, Node> nodeToAst = <ir.Node, Node>{};
 
   /// FIFO queue of work that needs to be completed before the returned AST
   /// nodes are correct.
   final Queue<WorkItem> workQueue = new Queue<WorkItem>();
 
   Kernel(this.compiler);
 
-  void addWork(Element element, WorkAction action) {
+  void addWork(Element element, void Function() action) {
     workQueue.addLast(new WorkItem(element, action));
   }
 
   void checkMember(Element key, ir.TreeNode value) {
     if (!checkedNodes.add(value)) return;
     if (value.parent == null) {
       internalError(key, "Missing parent on IR node.");
     }
     try {
       CheckParentPointers.check(value);
@@ skipping 638 matching lines @@
 }
 
 class ConstructorTarget {
   final ConstructorElement element;
   final DartType type;
 
   ConstructorTarget(this.element, this.type);
 
   String toString() => "ConstructorTarget($element, $type)";
 }