Use `Function` as function type syntax.

pkg/compiler/lib/compiler.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.
 
 library compiler;
 
 import 'dart:async';
 
 import 'package:package_config/packages.dart';
 
@@ skipping 11 matching lines @@
  * The source can be represented either as a [:List<int>:] of UTF-8 bytes or as
  * a [String].
  *
  * The following text is non-normative:
  *
  * It is recommended to return a UTF-8 encoded list of bytes because the scanner
  * is more efficient in this case. In either case, the data structure is
  * expected to hold a zero element at the last position. If this is not the
  * case, the entire data structure is copied before scanning.
  */
-typedef Future/*<String | List<int>>*/ CompilerInputProvider(Uri uri);
+typedef CompilerInputProvider = Future/*<String | List<int>>*/ Function(Uri);
 
 /// Deprecated, please use [CompilerInputProvider] instead.
-typedef Future<String> ReadStringFromUri(Uri uri);
+typedef ReadStringFromUri = Future<String> Function(Uri);
 
 /**
  * Returns an [EventSink] that will serve as compiler output for the given
  * component.
  *
  * Components are identified by [name] and [extension]. By convention,
  * the empty string [:"":] will represent the main script
  * (corresponding to the script parameter of [compile]) even if the
  * main script is a library. For libraries that are compiled
  * separately, the library name is used.
  *
  * At least the following extensions can be expected:
  *
  * * "js" for JavaScript output.
  * * "js.map" for source maps.
  * * "dart" for Dart output.
  * * "dart.map" for source maps.
  *
  * As more features are added to the compiler, new names and
  * extensions may be introduced.
  */
-typedef EventSink<String> CompilerOutputProvider(String name, String extension);
+typedef CompilerOutputProvider = EventSink<String> Function(String name, String extension);
 
 /**
  * Invoked by the compiler to report diagnostics. If [uri] is
  * [:null:], so are [begin] and [end]. No other arguments may be
  * [:null:]. If [uri] is not [:null:], neither are [begin] and
  * [end]. [uri] indicates the compilation unit from where the
  * diagnostic originates. [begin] and [end] are zero-based character
  * offsets from the beginning of the compilation unit. [message] is the
  * diagnostic message, and [kind] indicates indicates what kind of
  * diagnostic it is.
  */
-typedef void DiagnosticHandler(
-    Uri uri, int begin, int end, String message, Diagnostic kind);
+typedef DiagnosticHandler =
+    void Function(Uri, int begin, int end, String message, Diagnostic kind);
 
 /**
  * Provides a package lookup mechanism in the case that no package root or
  * package resolution configuration file are explicitly specified.
  */
-typedef Future<Packages> PackagesDiscoveryProvider(Uri uri);
+typedef PackagesDiscoveryProvider = Future<Packages> Function(Uri);
 
 /// Information resulting from the compilation.
 class CompilationResult {
   /// `true` if the compilation succeeded, that is, compilation didn't fail due
   /// to compile-time errors and/or internal errors.
   final bool isSuccess;
 
   /// The compiler object used for the compilation.
   ///
   /// Note: The type of [compiler] is implementation dependent and may vary.
@@ skipping 113 matching lines @@
   final String name;
 
   /**
    * This constructor is not private to support user-defined
    * diagnostic kinds.
    */
   const Diagnostic(this.ordinal, this.name);
 
   String toString() => name;
 }