LanguageFeatures/nnbd/null_promotion_A01_t08.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 A check of the form [e == null] or of the form [e is Null] where
/// [e] has static type [T] promotes the type of [e] to [Null] in the [true]
/// continuation, and to [NonNull(T)] in the [false] continuation.
///
/// @description Check that [e] is promoted to [NonNull(T)] in the [false]
/// condition. Test type aliases.
/// @author iarkh@unipro.ru

// Requirements=nnbd-strong

class A {
  foo() {}
}

typedef AAlias1 = A?;
typedef AAlias2 = AAlias1?;

dynamic init(x) => x;

main() {
  AAlias1 a1 = init(A());
  if (a1 is Null) {
  } else {
    a1.foo();
    AAlias1 a11 = a1;
    a11.foo();
  }

  if (a1 == null) {
  } else {
    a1.foo();
    AAlias1 a11 = a1;
  }

  AAlias2? a2 = init(A());
  if (a2 is Null) {
  } else {
    a2.foo();
    AAlias1 a22 = a1;
  }

  if (a2 == null) {
  } else {
    a2.foo();
    AAlias1 a22 = a1;
  }
}