Refactor Future constructors.

utils/pub/pub.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.
 
 /// The main entrypoint for the pub command line application.
 library pub;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:math';
@@ skipping 127 matching lines @@
     }
 
     var commandArgs = globalOptions.rest.sublist(1);
     command.run(cache, globalOptions, commandArgs);
   });
 }
 
 /// Checks that pub is running on a supported platform. If it isn't, it prints
 /// an error message and exits. Completes when the validation is done.
 Future validatePlatform() {
-  return new Future.of(() {
+  return new Future.sync(() {
     if (Platform.operatingSystem != 'windows') return;
 
     return runProcess('ver', []).then((result) {
       if (result.stdout.join('\n').contains('XP')) {
         log.error('Sorry, but pub is not supported on Windows XP.');
         exit(exit_codes.USAGE);
       }
     });
   });
 }
@@ skipping 101 matching lines @@
       if (globalOptions['trace'] && trace != null) {
         log.error(trace);
         log.dumpTranscript();
       } else {
         log.fine(trace);
       }
 
       exit(_chooseExitCode(error));
     }
 
-    new Future.of(() {
+    new Future.sync(() {
       if (requiresEntrypoint) {
         // TODO(rnystrom): Will eventually need better logic to walk up
         // subdirectories until we hit one that looks package-like. For now,
         // just assume the cwd is it.
         entrypoint = new Entrypoint(path.current, cache);
       }
 
       var commandFuture = onRun();
       if (commandFuture == null) return true;
 
@@ skipping 42 matching lines @@
     if (exception is HttpException || exception is HttpParserException ||
         exception is SocketIOException || exception is PubHttpException) {
       return exit_codes.UNAVAILABLE;
     } else if (exception is FormatException) {
       return exit_codes.DATA;
     } else {
       return 1;
     }
   }
 }