pkg/front_end/testcases/extension_types/issue54169.dart - sdk - Git at Google

 // Copyright (c) 2023, 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.

 extension type E1<X>(X it) {}
 typedef F<X> = X;
 extension type E2<X>(E1<F<E1<X>>> it) {}
	// Copyright (c) 2023, 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.

	extension type E1<X>(X it) {}
	typedef F<X> = X;
	extension type E2<X>(E1<F<E1<X>>> it) {}