Typing fixes to eliminate casts/dcalls

test/generated_sdk/lib/collection/hash_set.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.collection;
 
 /** Common parts of [HashSet] and [LinkedHashSet] implementations. */
 abstract class _HashSetBase<E> extends SetBase<E> {
 
   // The following two methods override the ones in SetBase.
@@ skipping 55 matching lines @@
    * If [isValidKey] is omitted, it defaults to testing if the object is an
    * [E] instance.
    *
    * If you supply one of [equals] and [hashCode],
    * you should generally also to supply the other.
    * An example would be using [identical] and [identityHashCode],
    * which is equivalent to using the shorthand [LinkedSet.identity]).
    */
   factory HashSet({ bool equals(E e1, E e2),
                     int hashCode(E e),
-                    bool isValidKey(potentialKey) }) {
+                    bool isValidKey(Object potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
           return new _HashSet<E>();
         }
         hashCode = _defaultHashCode;
       } else {
         if (identical(identityHashCode, hashCode) &&
             identical(identical, equals)) {
           return new _IdentityHashSet<E>();
@@ skipping 43 matching lines @@
   }
 
   /**
    * Provides an iterator that iterates over the elements of this set.
    *
    * The order of iteration is unspecified,
    * but consistent between changes to the set.
    */
   Iterator<E> get iterator;
 }