Fix Set.from which still had a generic type on the incoming Iterable.

tests/corelib/set_test.dart

 // Copyright (c) 2011, 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.
 
 library set_test;
 
 
 import 'package:expect/expect.dart';
 import "dart:collection";
 
@@ skipping 427 matching lines @@
   Expect.listEquals(ceList, set2.toList()..sort());
 
   Iterable<CE> ceIter = ceList.where((x) => true);
   Set<CE> set3 = setFrom(ceIter);
   Expect.listEquals(ceList, set3.toList()..sort());
 
   Set<CE> set4 = setFrom(new Iterable.generate(0));
   Expect.isTrue(set4.isEmpty);
 }
 
+class A {}
+class B {}
+class C implements A, B {}
+
+void testASetFrom(setFrom) {
+  List<B> bList= <B>[new C()];
+  // Set.from allows to cast elements.
+  Set<A> aSet = setFrom(bList);
+  Expect.isTrue(aSet.length == 1);
+}
+
 main() {
   testMain(() => new HashSet());
   testMain(() => new LinkedHashSet());
   testMain(() => new HashSet.identity());
   testMain(() => new LinkedHashSet.identity());
   testMain(() => new HashSet(equals: identical));
   testMain(() => new LinkedHashSet(equals: identical));
   testMain(() => new HashSet(equals: (a, b) => a == b,
                              hashCode: (a) => -a.hashCode,
                              isValidKey: (a) => true));
@@ skipping 43 matching lines @@
   testIntSetFrom((x) => new SplayTreeSet<int>.from(x));
 
   testCESetFrom((x) => new Set<CE>.from(x));
   testCESetFrom((x) => new HashSet<CE>.from(x));
   testCESetFrom((x) => new LinkedHashSet<CE>.from(x));
   testCESetFrom((x) => new SplayTreeSet<CE>.from(x));
 
   testCESetFrom((x) => new SplayTreeSet<CE>.from(x,
                                                  customCompare(20), validKey));
   testCESetFrom((x) => new SplayTreeSet<CE>.from(x, identityCompare));
+
+  testASetFrom((x) => new Set<A>.from(x));
+  testASetFrom((x) => new HashSet<A>.from(x));
+  testASetFrom((x) => new LinkedHashSet<A>.from(x));
+  testASetFrom((x) => new SplayTreeSet<A>.from(x));
 }