pkg/front_end/testcases/inference_update_3/if_null_test.dart

// Copyright (c) 2024, 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.

// Tests the functionality proposed in
// https://github.com/dart-lang/language/issues/1618#issuecomment-1507241494,
// using if-null expressions.

/// Ensures a context type of `Iterable<T>` for the operand, or `Iterable<_>` if
/// no type argument is supplied.
Iterable<T> contextIterable<T>(Iterable<T> x) => x;

class A {}

class B1<T> implements A {}

class B2<T> implements A {}

class C1<T> implements B1<T>, B2<T> {}

class C2<T> implements B1<T>, B2<T> {}

/// Ensures a context type of `B1<T>` for the operand, or `B1<_>` if no type
/// argument is supplied.
B1<T> contextB1<T>(B1<T> x) => x;

main() {
  var c1IntQuestion = null as C1<int>?;
  var c2Double = C2<double>();
  contextB1(c1IntQuestion ?? c2Double);

  var iterableIntQuestion = null as Iterable<int>?;
  var listNum = <num>[];
  contextIterable<num>(iterableIntQuestion ?? listNum);
}