Language/Generics/parameter_A01_t04.dart

/*
 * Copyright (c) 2019, 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
 *    typeParameter ::= metadata identifier (extends typeNotVoid)?
 *    typeParameters ::= ‘<’ typeParameter (‘,’ typeParameter)* ‘>’
 * A type parameter [T] may be suffixed with an [extends] clause that specifies
 * the upper bound for [T].
 * @description Statically checks that [extends] clause specifies upper bound
 * for the class type parameter
 * @author iarkh@unipro.ru
 */

class A {} 
class B extends A {}
class C extends B {}

typedef Alias1<T extends A>(T t);
typedef Alias2<T extends B>(T t);
typedef Alias3<T extends C>(T t);

testme(a) {}

main() {
  Alias1 a1 = testme;
  Alias1<A> a2 = testme;
  Alias1<B> a3 = testme;
  Alias1<C> a4 = testme;

  Alias2 a5 = testme;
  Alias2<A> a6 = testme;
  //     ^
  // [analyzer] COMPILE_TIME_ERROR.TYPE_ARGUMENT_NOT_MATCHING_BOUNDS
  //        ^
  // [cfe] Type argument 'A' doesn't conform to the bound 'B' of the type variable 'T' on 'Alias2'.
  Alias2<B> a7 = testme;
  Alias2<C> a8 = testme;

  Alias3 a9 = testme;
  Alias3<A> a10 = testme;
  //     ^
  // [analyzer] COMPILE_TIME_ERROR.TYPE_ARGUMENT_NOT_MATCHING_BOUNDS
  //        ^
  // [cfe] Type argument 'A' doesn't conform to the bound 'C' of the type variable 'T' on 'Alias3'.
  Alias3<B> a11 = testme;
  //     ^
  // [analyzer] COMPILE_TIME_ERROR.TYPE_ARGUMENT_NOT_MATCHING_BOUNDS
  //        ^
  // [cfe] Type argument 'B' doesn't conform to the bound 'C' of the type variable 'T' on 'Alias3'.
  Alias3<C> a12 = testme;
}