LanguageFeatures/Generic-functions-as-type-args/least_greatest_closure_t01.dart

// Copyright (c) 2020, 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.

/// @assertion The definitions of least and greatest closure are changed in null
/// safe libraries to substitute [Never] in positions where previously [Null
/// would have been substituted, and [Object?] in positions where previously
/// [Object] or [dynamic] would have been substituted.
/// @description Check that correct type is substituted for generic
/// [void Function<T>()] typedef.
/// @note Read more about the least and greatest closure test template:
/// https://github.com/dart-lang/co19/issues/575#issuecomment-613542349
///
/// $Issue 45763
///
/// @author iarkh@unipro.ru

// SharedOptions=--enable-experiment=generic-metadata

import "../../Utils/expect.dart";

typedef check = void Function<T>();

void main() {
  void f(check Function<T>() g) => g();
  Expect.throws(() { f(<T>() => captureTypeArgument()); });
  Expect.equals(typeOf<void Function<T>()>(), capturedTypeArgument);
}