Make List.skip, List.take and List.reversed return Iterables, not Lists.

tests/corelib/list_reversed_test.dart

Index: tests/corelib/list_reversed_test.dart
diff --git a/tests/corelib/list_reversed_test.dart b/tests/corelib/list_reversed_test.dart
index 03b99ce4432d72224a96914557b47b79bdde41c0..1e12d527378627f35ab915d4469e735ca0af8b7d 100644
--- a/tests/corelib/list_reversed_test.dart
+++ b/tests/corelib/list_reversed_test.dart
@@ -7,6 +7,11 @@ main() {
   testOperations();
 }
 
+class ThrowMarker {
+  const ThrowMarker();
+  String toString() => "<<THROWS>>";
+}
+
 void testOperations() {
   // Comparison lists.
   List l = const [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
@@ -14,27 +19,118 @@ void testOperations() {
   // A base list that starts out like l.
   List base = l.toList();
   // A lazy reverse of base.
-  List reversed = base.reversed;
+  Iterable reversed = base.reversed;
 
-  Expect.listEquals(r, reversed);
-  Expect.listEquals(l, reversed.reversed);
+  Expect.listEquals(r, reversed.toList());
+  Expect.listEquals(l, reversed.toList().reversed.toList());
   for (int i = 0; i < r.length; i++) {
-    Expect.equals(r[i], reversed[i]);
+    Expect.equals(r[i], reversed.elementAt(i));
   }
   Expect.equals(4, base.indexOf(5));
-  Expect.equals(5, reversed.indexOf(5));
+  Expect.equals(5, reversed.toList().indexOf(5));
 
-  // Combinations of start and end relative to start/end of list.
+  // Reversed followed by combinations of skip and take.
   List subr = [8, 7, 6, 5, 4, 3];
-  Expect.listEquals(subr, reversed.skip(2).take(6));
-  Expect.listEquals(subr, reversed.take(8).skip(2));
-  Expect.listEquals(subr, reversed.reversed.skip(2).take(6).reversed);
-  Expect.listEquals(subr, reversed.reversed.take(8).skip(2).reversed);
-  Expect.listEquals(subr, reversed.take(8).reversed.take(6).reversed);
-  Expect.listEquals(subr, reversed.reversed.take(8).reversed.take(6));
-  Expect.listEquals(subr, reversed.reversed.skip(2).reversed.skip(2));
-  Expect.listEquals(subr, reversed.skip(2).reversed.skip(2).reversed);
+  Expect.listEquals(subr, reversed.skip(2).take(6).toList());
+  Expect.listEquals(subr, reversed.take(8).skip(2).toList());
+  Expect.listEquals(subr,
+      reversed.toList().reversed.skip(2).take(6).toList().reversed.toList());
+  Expect.listEquals(subr,
+      reversed.toList().reversed.take(8).skip(2).toList().reversed.toList());
+  Expect.listEquals(subr,
+      reversed.take(8).toList().reversed.take(6).toList().reversed.toList());
+  Expect.listEquals(subr,
+      reversed.toList().reversed.take(8).toList().reversed.take(6).toList());
+  Expect.listEquals(subr,
+      reversed.toList().reversed.skip(2).toList().reversed.skip(2).toList());
+  Expect.listEquals(subr,
+      reversed.skip(2).toList().reversed.skip(2).toList().reversed.toList());
+
+
+  void testList(List list) {
+    var throws = const ThrowMarker();
+    void testEquals(v1, v2, path) {
+      if (v1 is Iterable) {
+        Iterator i1 = v1.iterator;
+        Iterator i2 = v2.iterator;
+        int index = 0;
+        while (i1.moveNext()) {
+          Expect.isTrue(i2.moveNext(),
+              "Too few actual values. Expected[$index] == ${i1.current}");
+          testEquals(i1.current, i2.current, "$path[$index]");
+          index++;
+        }
+        Expect.isFalse(i2.moveNext(),
+              "Too many actual values. Actual[$index] == ${i2.current}");
+      } else {
+        Expect.equals(v1, v2, path);
+      }
+    }
+
+    void testOp(operation(Iterable reversedList), name) {
+      List reversedList = new List(list.length);
+      for (int i = 0; i < list.length; i++) {
+        reversedList[i] = list[list.length - 1 - i];
+      }
+      Iterable reversed = list.reversed;
+      var expect;
+      try {
+        expect = operation(reversedList);
+      } catch (e) {
+        print(e);
+        expect = throws;
+      }
+      var actual;
+      try {
+        actual = operation(reversed);
+      } catch (e) {
+        print(e);
+        actual = throws;
+      }
+      testEquals(expect, actual, "$name: $list");
+    }
+    testOp((i) => i.first, "first");
+    testOp((i) => i.last, "last");
+    testOp((i) => i.single, "single");
+    testOp((i) => i.firstMatching((n) => n < 5), "firstMatching<5");
+    testOp((i) => i.firstMatching((n) => n < 10), "firstMatching<10");
+    testOp((i) => i.lastMatching((n) => n < 5), "lastMatching<5");
+    testOp((i) => i.lastMatching((n) => n < 10), "lastMatching<10");
+    testOp((i) => i.singleMatching((n) => n < 5), "singelMatching<5");
+    testOp((i) => i.singleMatching((n) => n < 10), "singelMatching<10");
+    testOp((i) => i.contains(5), "contains(5)");
+    testOp((i) => i.contains(10), "contains(10)");
+    testOp((i) => i.any((n) => n < 5), "any<5");
+    testOp((i) => i.any((n) => n < 10), "any<10");
+    testOp((i) => i.every((n) => n < 5), "every<5");
+    testOp((i) => i.every((n) => n < 10), "every<10");
+    testOp((i) => i.max(), "max");
+    testOp((i) => i.min(), "min");
+    testOp((i) => i.reduce(0, (a, b) => a + b), "reduce-sum");
+    testOp((i) => i.join("-"), "join-");
+    testOp((i) => i.join(""), "join");
+    testOp((i) => i.join(), "join-null");
+    testOp((i) => i.map((n) => n * 2), "map*2");
+    testOp((i) => i.where((n) => n < 5), "where<5");
+    testOp((i) => i.where((n) => n < 10), "where<10");
+    testOp((i) => i.expand((n) => []), "expand[]");
+    testOp((i) => i.expand((n) => [n]), "expand[n]");
+    testOp((i) => i.expand((n) => [n, n]), "expand[n, n]");
+  }
+
+  // Combinations of lists with 0, 1 and more elements.
+  testList([]);
+  testList([0]);
+  testList([10]);
+  testList([0, 1]);
+  testList([0, 10]);
+  testList([10, 11]);
+  testList([0, 5, 10]);
+  testList([10, 5, 0]);
+  testList([0, 1, 2, 3]);
+  testList([3, 4, 5, 6]);
+  testList([10, 11, 12, 13]);
 
   // Reverse const list.
-  Expect.listEquals(r, l.reversed);
+  Expect.listEquals(r, l.reversed.toList());
 }