Don't try to box immutable objects.

tests/language/src/Closure4Test.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.
+
+// Having a declared function being captured within self tripped the dart2js

[ngeoffray, 2012/04/17 13:06:12]

self tripped -> used to self trip

[floitsch, 2012/04/17 13:09:00]

that's not what I wanted to say. But reworded.

+// compiler.
+
+foo(f) => f(499);
+
+main() {
+  void fun(x) {
+    if (x < 3) {
+      return foo((x) => fun(x));
+    } else {
+      return x;
+    }
+  }
+  Expect.equals(499, fun(499));
+}