Implement least upper bound.

sdk/lib/io/link.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;
 
 /**
  * [Link] objects are references to filesystem links.
  *
  */
@@ skipping 148 matching lines @@
   Link get absolute => new Link(_absolutePath);
 
   Future<FileStat> stat() => FileStat.stat(path);
 
   FileStat statSync() => FileStat.statSync(path);
 
   Future<Link> create(String target, {bool recursive: false}) {
     if (Platform.operatingSystem == 'windows') {
       target = _makeWindowsLinkTarget(target);
     }
-    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_LINK, [path, target]))
       .then((response) {
         if (_isErrorResponse(response)) {
           throw _exceptionFromResponse(
               response, "Cannot create link to target '$target'", path);
         }
         return this;
       });
   }
 
@@ skipping 110 matching lines @@
         return new ArgumentError();
       case _OSERROR_RESPONSE:
         var err = new OSError(response[_OSERROR_RESPONSE_MESSAGE],
                               response[_OSERROR_RESPONSE_ERROR_CODE]);
         return new FileSystemException(message, path, err);
       default:
         return new Exception("Unknown error");
     }
   }
 }