Add List.insert.

tests/corelib/list_insert_at_test.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
 void main() {
   // Normal modifiable list.
   var l1 = [0, 1, 2, 3, 4];
 
   bool checkedMode = false;
   assert(checkedMode = true);
 
   // Index must be integer and in range.
-  Expect.throws(() { l1.removeAt(-1); },
+  Expect.throws(() { l1.insertAt(-1, 5); },
                 (e) => e is RangeError,
                 "negative");
-  Expect.throws(() { l1.removeAt(5); },
+  Expect.throws(() { l1.insertAt(6, 5); },
                 (e) => e is RangeError,
                 "too large");
-  Expect.throws(() { l1.removeAt(null); },
+  Expect.throws(() { l1.insertAt(null, 5); },
                 (e) => e is ArgumentError,
                 "too large");
-  Expect.throws(() { l1.removeAt("1"); },
+  Expect.throws(() { l1.insertAt("1", 5); },
                 (e) => (checkedMode ? e is TypeError
                                     : e is ArgumentError),
                 "string");
-  Expect.throws(() { l1.removeAt(1.5); },
+  Expect.throws(() { l1.insertAt(1.5, 5); },
                 (e) => (checkedMode ? e is TypeError
                                     : e is ArgumentError),
                 "double");
 
-  Expect.equals(2, l1.removeAt(2), "l1-remove2");
-  Expect.equals(1, l1[1], "l1-1[1]");
+  l1.insertAt(5, 5);
+  Expect.equals(6, l1.length);
+  Expect.equals(5, l1[5]);
+  Expect.equals("[0, 1, 2, 3, 4, 5]", l1.toString());
 
-  Expect.equals(3, l1[2], "l1-1[2]");
-  Expect.equals(4, l1[3], "l1-1[3]");
-  Expect.equals(4, l1.length, "length-1");
-
-  Expect.equals(0, l1.removeAt(0), "l1-remove0");
-  Expect.equals(1, l1[0], "l1-2[0]");
-  Expect.equals(3, l1[1], "l1-2[1]");
-  Expect.equals(4, l1[2], "l1-2[2]");
-  Expect.equals(3, l1.length, "length-2");
+  l1.insertAt(0, -1);
+  Expect.equals(7, l1.length);
+  Expect.equals(-1, l1[0]);
+  Expect.equals("[-1, 0, 1, 2, 3, 4, 5]", l1.toString());
 
   // Fixed size list.
   var l2 = new List(5);
   for (var i = 0; i < 5; i++) l2[i] = i;
-  Expect.throws(() { l2.removeAt(2); },
+  Expect.throws(() { l2.insertAt(2, 5); },
                 (e) => e is UnsupportedError,
                 "fixed-length");
 
   // Unmodifiable list.
   var l3 = const [0, 1, 2, 3, 4];
-  Expect.throws(() { l3.removeAt(2); },
+  Expect.throws(() { l3.insertAt(2, 5); },
                 (e) => e is UnsupportedError,
                 "unmodifiable");
 
   // Empty list is not special.
   var l4 = [];
-  Expect.throws(() { l4.removeAt(0); },
-                (e) => e is RangeError,
-                "empty");
+  l4.insertAt(0, 499);
+  Expect.equals(1, l4.length);
+  Expect.equals(499, l4[0]);
 }