Migrate test block 113 to Dart 2.0.

tests/language_2/generic_functions_test.dart

 // Copyright (c) 2016, 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.
 //
 // VMOptions=--generic-method-syntax
 
 /// Dart test verifying that the parser can handle type parameterization of
 /// function declarations and function invocations. Variant of code from
 /// DEP #22, adjusted to use generic top level functions.
 
@@ skipping 83 matching lines @@
 main() {
   BinaryTree<num, String> sT = new BinaryTree<num, String>.empty();
 
   sT = sT.insert(0, "");
   sT = sT.insert(1, " ");
   sT = sT.insert(2, "  ");
   sT = sT.insert(3, "   ");
 
   BinaryTree<num, num> iT = sT.map<num>((String s) => s.length);
 
-  Expect.equals(iT.foldPre<num>(0, (int i, num s) => i + s), 6);
+  Expect.equals(iT.foldPre<num>(0, (num i, num s) => i + s), 6);
 }