Add test inspired by Leg bug.

dart/tests/language/src/Closure3Test.dart

Index: dart/tests/language/src/Closure3Test.dart
diff --git a/dart/tests/language/src/Closure3Test.dart b/dart/tests/language/src/Closure3Test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3597eb6a38302ff4b3b6a6eb879f740b65f8222e
--- /dev/null
+++ b/dart/tests/language/src/Closure3Test.dart
@@ -0,0 +1,20 @@
+// Copyright (c) 2012, 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.
+
+// Test that a NullPointerException is thrown even when an expression
+// seems to be free of side-effects.
+
+test(x, y) {
+  (() { x - y; })();
+}
+
+main() {
+  try {
+    test(null, 2);
+    Expect.fail('Expected NullPointerException');
+  } catch (NullPointerException ex) {
+    return;
+  }
+  Expect.fail('Expected NullPointerException');
+}