tests/language/null_is_bottom_test.dart

// Copyright (c) 2016, 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.

// Test that Null is a subtype of any other type.

import 'package:expect/expect.dart';

class A {}
typedef A ReturnA();
typedef TakeA(A a);
typedef Null ReturnNull();
typedef TakeNull(Null n);

@NoInline()
testA(A a) {}

@NoInline()
testListA(List<A> list) {}

@NoInline()
testIsListA(var a) => a is List<A>;

@NoInline()
testAsListA(var a) => a as List<A>;

@NoInline()
testNull(Null n) {}

@NoInline()
testListNull(List<Null> list) {}

@NoInline()
testIsListNull(var a) => a is List<Null>;

@NoInline()
testAsListNull(var a) => a as List<Null>;

@NoInline()
testReturnA(ReturnA f) {}

@NoInline()
testIsReturnA(var f) => f is ReturnA;

@NoInline()
testAsReturnA(var f) => f as ReturnA;

@NoInline()
testReturnNull(ReturnNull f) {}

@NoInline()
testIsReturnNull(var f) => f is ReturnNull;

@NoInline()
testAsReturnNull(var f) => f as ReturnNull;

@NoInline()
testTakeA(TakeA f) {}

@NoInline()
testIsTakeA(var f) => f is TakeA;

@NoInline()
testAsTakeA(var f) => f as TakeA;

@NoInline()
testTakeNull(TakeNull f) {}

@NoInline()
testIsTakeNull(var f) => f is TakeNull;

@NoInline()
testAsTakeNull(var f) => f as TakeNull;

Null returnNullFunc() => null;
takeNullFunc(Null n) {}
A returnAFunc() => null;
takeAFunc(A a) {}

main() {
  var n = null;
  var listNull = new List<Null>();
  var a = new A();
  var listA = new List<A>();

  testA(n);                                                          /// 01: ok
  testA(a);                                                          /// 02: ok
  testListA(listNull);                                               /// 03: ok
  testListA(listA);                                                  /// 04: ok
  Expect.isTrue(testIsListA(listNull));                              /// 05: ok
  Expect.isTrue(testIsListA(listA));                                 /// 06: ok
  testAsListA(listNull);                                             /// 07: ok
  testAsListA(listA);                                                /// 08: ok

  testNull(n);                                                       /// 09: ok
  testNull(a);                                       /// 10: dynamic type error
  testListNull(listNull);                                            /// 11: ok
  testListNull(listA);                               /// 12: dynamic type error
  Expect.isTrue(testIsListNull(listNull));                           /// 13: ok
  Expect.isFalse(testIsListNull(listA));                             /// 14: ok
  testAsListNull(listNull);                                          /// 15: ok
  Expect.throws(() => testAsListNull(listA), (e) => e is CastError); /// 16: ok

  var returnNull = returnNullFunc;
  var takeNull = takeNullFunc;
  var returnA = returnAFunc;
  var takeA = takeAFunc;

  testReturnA(returnA);                                              /// 17: ok
  testReturnA(returnNull);                                           /// 18: ok
  Expect.isTrue(testIsReturnA(returnA));                             /// 19: ok
  Expect.isTrue(testIsReturnA(returnNull));                          /// 20: ok
  testAsReturnA(returnA);                                            /// 21: ok
  testAsReturnA(returnNull);                                         /// 22: ok

  // This is not valid in strong-mode: ()->A <: ()->Null
  testReturnNull(returnA);                                           /// 23: ok
  testReturnNull(returnNull);                                        /// 24: ok
  // This is not valid in strong-mode: ()->A <: ()->Null
  Expect.isTrue(testIsReturnNull(returnA));                          /// 25: ok
  Expect.isTrue(testIsReturnNull(returnNull));                       /// 26: ok
  // This is not valid in strong-mode: ()->A <: ()->Null
  testAsReturnNull(returnA);                                         /// 27: ok
  testAsReturnNull(returnNull);                                      /// 28: ok

  testTakeA(takeA);                                                  /// 29: ok
  // This is not valid in strong-mode: (Null)-> <: (A)->
  testTakeA(takeNull);                                               /// 30: ok
  Expect.isTrue(testIsTakeA(takeA));                                 /// 31: ok
  // This is not valid in strong-mode: (Null)-> <: (A)->
  Expect.isTrue(testIsTakeA(takeNull));                              /// 32: ok
  testAsTakeA(takeA);                                                /// 33: ok
  // This is not valid in strong-mode: (Null)-> <: (A)->
  testAsTakeA(takeNull);                                             /// 34: ok

  testTakeNull(takeA);                                               /// 35: ok
  testTakeNull(takeNull);                                            /// 36: ok
  Expect.isTrue(testIsTakeNull(takeA));                              /// 37: ok
  Expect.isTrue(testIsTakeNull(takeNull));                           /// 38: ok
  testAsTakeNull(takeA);                                             /// 39: ok
  testAsTakeNull(takeNull);                                          /// 40: ok
}