Implement least upper bound.

sdk/lib/io/file_impl.dart

 // Copyright (c) 2013, 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 dart.io;
 
 // Read the file in blocks of size 64k.
 const int _BLOCK_SIZE = 64 * 1024;
 
 
@@ skipping 239 matching lines @@
     return result;
   }
 
   File get absolute => new File(_absolutePath);
 
   Future<FileStat> stat() => FileStat.stat(path);
 
   FileStat statSync() => FileStat.statSync(path);
 
   Future<File> create({bool recursive: false}) {
-    return (recursive ? parent.create(recursive: true)
-                      : new Future.value(null))
+    var result = recursive ? parent.create(recursive: true)
+                           : new Future.value(null);
+    return result
       .then((_) => _IOService.dispatch(_FILE_CREATE, [path]))
       .then((response) {
         if (_isErrorResponse(response)) {
           throw _exceptionFromResponse(response, "Cannot create file", path);
         }
         return this;
       });
   }
 
   external static _create(String path);
@@ skipping 617 matching lines @@
 
   void _checkAvailable() {
     if (_asyncDispatched) {
       throw new FileSystemException("An async operation is currently pending", path);
     }
     if (closed) {
       throw new FileSystemException("File closed", path);
     }
   }
 }