List.mappedBy/skip/take returns a List.

tests/corelib/iterable_mapping_test.dart

Index: tests/corelib/iterable_mapping_test.dart
diff --git a/tests/corelib/iterable_mapping_test.dart b/tests/corelib/iterable_mapping_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..4278169bd1424f57d15e7e42d3675bdc3073875c
--- /dev/null
+++ b/tests/corelib/iterable_mapping_test.dart
@@ -0,0 +1,57 @@
+// 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.
+
+main() {
+  List<int> list1 = <int>[1, 2, 3];
+  List<int> list2 = const <int>[4, 5];
+  List<String> list3 = <String>[];
+  Set<int> set1 = new Set<int>();
+  set1..add(11)

[Lasse Reichstein Nielsen, 2013/01/24 06:49:32]

Why not set1.addAll([1, 2, 3]); ?
What is the purpose of creating it like this (i.e., needs comment).

[floitsch, 2013/01/24 13:48:34]

Done.

+      ..add(12)
+      ..add(13);
+  Set set2 = new Set();
+
+  Iterable mapped = list1.mappedBy((x) => x + 1);

[Lasse Reichstein Nielsen, 2013/01/24 06:49:32]

Why "Iterable" and not "List"?

[floitsch, 2013/01/24 13:48:34]

Because I want to prepare for the change back.

+  Expect.isTrue(mapped is List);
+  Expect.listEquals([2, 3, 4], mapped.toList());

[Lasse Reichstein Nielsen, 2013/01/24 06:49:32]

And why .toList then?

[floitsch, 2013/01/24 13:48:34]

removed.

+
+  mapped = mapped.mappedBy((x) => x + 1);
+  Expect.isTrue(mapped is List);
+  Expect.listEquals([3, 4, 5], mapped.toList());
+
+  mapped = list2.mappedBy((x) => x + 1);
+  Expect.isTrue(mapped is List);
+  Expect.listEquals([5, 6], mapped.toList());
+
+  mapped = mapped.mappedBy((x) => x + 1);
+  Expect.isTrue(mapped is List);
+  Expect.listEquals([6, 7], mapped.toList());
+
+  mapped = list3.mappedBy((x) => x + 1);
+  Expect.isTrue(mapped is List);
+  Expect.listEquals([], mapped.toList());
+
+  mapped = mapped.mappedBy((x) => x + 1);
+  Expect.isTrue(mapped is List);
+  Expect.listEquals([], mapped.toList());
+
+  var expected = new Set<int>()..add(12)..add(13)..add(14);
+  mapped = set1.mappedBy((x) => x + 1);
+  Expect.isFalse(mapped is List);
+  Expect.setEquals(expected, mapped.toSet());
+
+  expected = new Set<int>()..add(13)..add(14)..add(15);
+  mapped = mapped.mappedBy((x) => x + 1);
+  Expect.isFalse(mapped is List);
+  Expect.setEquals(expected, mapped.toSet());
+
+  mapped = set2.mappedBy((x) => x + 1);
+  Expect.isFalse(mapped is List);
+  Expect.listEquals([], mapped.toList());
+
+  mapped = mapped.mappedBy((x) => x + 1);
+  Expect.isFalse(mapped is List);
+  Expect.listEquals([], mapped.toList());
+
+}