LanguageFeatures/nnbd/flow-analysis/promotion_via_assignment_A03_t01.dart

// Copyright (c) 2020, 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 We say that a variable x is promotable via assignment of an
/// expression of type T given variable model VM if
///
///  VM = VariableModel(declared, promoted, tested, assigned, unassigned,
///  captured)
///  and captured is false
///  and S is the current type of x in VM
///  and T <: S and not S <: T
///  and T is a type of interest for x in tested
///
/// @description Checks that if T <: S and S <: T then promotion via assignment
/// is not performed
///
/// @author sgrekhov@unipro.ru

// Requirements=nnbd-strong
import '../../../Utils/expect.dart';

class S {}
class T extends S {
  int foo() => 42;
}

main() {
  dynamic x = new S();
  if (x is T) {
    // nothing
  }
  x = new T();
  x.foo();
  Expect.throws(() {
    x.bar();
  }, (e) => e is NoSuchMethodError);
}