Capture this.

frog/tests/leg_only/src/ClosureCapture3Test.dart

+// 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.
+
+class Closure {
+  var x;
+  Closure(val) : this.x = val;
+
+  foo() {
+    return fun() {
+      return x;
+    };
+  }
+
+  bar() {
+    return fun() {
+      return toto();
+    };
+  }
+
+  toto() {
+    return x + 1;
+  }
+
+  nestedClosure() {
+    var f = g() { return x; };
+    return fun() { return f() + 2; };
+  }
+}
+
+main() {
+  var c = new Closure(499);
+  var f = c.foo();
+  Expect.equals(499, f());
+  Expect.equals(500, c.bar()());
+  Expect.equals(501, c.nestedClosure()());
+}