Make dart:core strong-mode clean.

sdk/lib/core/num.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.
 
 part of dart.core;
 
 /**
  * An integer or floating-point number.
  *
  * It is a compile-time error for any type other than [int] or [double]
@@ skipping 421 matching lines @@
    * If no [onError] is supplied, it defaults to a function that throws a
    * [FormatException].
    *
    * For any number `n`, this function satisfies
    * `identical(n, num.parse(n.toString()))` (except when `n` is a NaN `double`
    * with a payload).
    */
   static num parse(String input, [num onError(String input)]) {
     String source = input.trim();
     // TODO(lrn): Optimize to detect format and result type in one check.
-    num result = int.parse(source, onError: _returnNull);
+    num result = int.parse(source, onError: _returnIntNull);
     if (result != null) return result;
-    result = double.parse(source, _returnNull);
+    result = double.parse(source, _returnDoubleNull);
     if (result != null) return result;
     if (onError == null) throw new FormatException(input);
     return onError(input);
   }
 
-  /** Helper function for [parse]. */
-  static _returnNull(_) => null;
+  /** Helper functions for [parse]. */
+  static int _returnIntNull(String _) => null;
+  static double _returnDoubleNull(String _) => null;
 }