tests/language/implicit_downcast_during/if_null_assignment_test.dart

// Copyright (c) 2017, 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.

class A {}

class B extends A {}

void main() {
  B? b;
  var a = new B() as A?;
  b ??= a;
//      ^
// [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
// [cfe] A value of type 'A?' can't be assigned to a variable of type 'B?'.
}