- Add a test for context cycles. Based on dartbug.com/7681.

tests/language/closure_cycles_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.
+// Based on dartbug.com/7681
+// Verify that context chains do not lead to unintended memory being held.
+
+library closure_cycles_test;
+
+import "dart:async";
+
+class X {
+  Function onX;
+  X() { new Timer(0, (_) => onX(new Y())); }
+}
+
+class Y {
+  Function onY;
+  var heavyMemory;
+  static var count = 0;
+  Y() {
+    // Consume large amounts of memory per iteration to fail/succeed quicker.
+    heavyMemory = new List(10*1024*1024);
+    // Terminate the test if we allocated enough memory without running out.
+    if (count++ > 100) return;
+    new Timer(0, (_) => onY());
+  }
+}
+
+void doIt() {
+  var x = new X();
+  x.onX = (y) {
+    y.onY = () {
+      y;  // Capturing y can lead to endless context chains!
+      doIt();
+    };
+  };
+}
+
+void main() {
+  doIt();
+}