Migrated test block 26 to Dart 2.0.

tests/corelib_2/splay_tree_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.
 
 // Dart test for Splaytrees.
 library splay_tree_test;
 
 import "package:expect/expect.dart";
 import 'dart:collection';
 
@@ skipping 107 matching lines @@
   for (int i = 0; i < 3; i++) {
     Expect.isTrue(map.containsKey(key(i)));
     Expect.equals(i, map[key(i)]);
   }
   Expect.isFalse(map.containsKey(key(5)));
   Expect.isFalse(map.containsKey(1));
   Expect.isFalse(map.containsKey("string"));
   Expect.equals(null, map[key(5)]);
   Expect.equals(null, map[1]);
   Expect.equals(null, map["string"]);
-  Expect.throws(() {
-    map[1] = 42;
-  });
-  Expect.throws(() {
-    map["string"] = 42;
-  });
+  map[1] = 42; //# 01: compile-time error
+  map["string"] = 42; //# 02: compile-time error
   map[key(5)] = 42;
   Expect.equals(4, map.length);
   Expect.equals(42, map[key(5)]);
 }
 
 class IncomparableKey {
   final int id;
   IncomparableKey(this.id);
 }