Rename XMatching to XWhere.

pkg/args/lib/args.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.
 
 /**
  * This library lets you define parsers for parsing raw command-line arguments
  * into a set of options and values using [GNU][] and [POSIX][] style options.
  *
  * ## Defining options ##
  *
@@ skipping 313 matching lines @@
       throw new ArgumentError('No option named $option');
     }
     return options[option].defaultValue;
   }
 
   /**
    * Finds the option whose abbreviation is [abbr], or `null` if no option has
    * that abbreviation.
    */
   Option findByAbbreviation(String abbr) {
-    return options.values.firstMatching((option) => option.abbreviation == abbr,
+    return options.values.firstWhere((option) => option.abbreviation == abbr,
         orElse: () => null);
   }
 }
 
 /**
  * A command-line option. Includes both flags and options which take a value.
  */
 class Option {
   final String name;
   final String abbreviation;
@@ skipping 48 matching lines @@
           'Could not find an option named "$name".');
     }
 
     return _options[name];
   }
 
   /** Get the names of the options as a [Collection]. */
   Collection<String> get options => _options.keys.toList(growable: false);
 }