LanguageFeatures/Constructor-tear-offs/call_method_A04_t01.dart

// Copyright (c) 2021, 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 Currently you can do instantiated tear-offs of instance methods.
/// We restrict that to interface methods, which precisely excludes the call
/// methods of function types. We do not allow instantiating function values,
/// and therefore also cannot allow side-stepping that restriction by
/// instantiation the .call "instance" method of such a value.
///
/// That makes it a compile-time error to explicitly instantiate the call method
/// of an expression with a function type or of type Function, and the tear-off
/// of a call method of a function type is not subject to implicit instantiation
/// (so the tear-off is always generic, even if the context type requires it not
/// to be, which is then guaranteed to introduce a type error).
///
/// @description Checks that it is allowed to tear-off a 'call' method of a
/// user defined classes
/// @author sgrekhov@unipro.ru

// SharedOptions=--enable-experiment=constructor-tearoffs

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

class C {
  T call<T>(T t) => t;
}

main() {
  C c = new C();
  int Function(int) f = c.call;
  Expect.equals(42, f(42));
}