| // 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 With sound null safety, all generic const constructors and |
| /// generic const literals are evaluated using the actual type arguments |
| /// provided, whether legacy or non-legacy. This ensures that with sound null |
| /// safety, the final consistent semantics are obeyed. |
| /// |
| /// @description Checks dynamically that actual generic class type parameter is |
| /// evaluated correctly for [Never] type argument in weak mode. |
| /// |
| /// This is a question about constant evaluation, and the distinction between |
| /// sound and unsound null checking pops up: The null safety spec says that with |
| /// unsound null checking, `const C<Never>()` should treat `Never` as if it were |
| /// a legacy type. https://github.com/dart-lang/language/issues/1346 is all about |
| /// this, and we can't resolve that question as long as 1346 hasn't been |
| /// resolved. |
| /// |
| /// One proposal says that in unsound checking mode, `const C<Never>()` means |
| /// `const C<Null>()`, so the type argument will be unequal to `Never`. Another |
| /// one is that we should add `*` to types and leave `Never` in opted-in code |
| /// unchanged, so we'd compare `Never` and `Never*`, which would yield true |
| /// (according to the run-time semantics of `operator ==` on instances of `Type` |
| /// that reify types). |
| /// |
| /// So we'll have to keep this one on a waiting list, blocked by 1346 (or some |
| /// issue that can be found looking at 1346, if the discussion is taken somewhere |
| /// else, say https://github.com/dart-lang/sdk/issues/44246). |
| /// |
| /// @Issue 39678 |
| /// @author iarkh@unipro.ru |
| |
| // Requirements=nnbd-weak |
| |
| import "../../../Utils/expect.dart"; |
| |
| class A<T> { |
| const A(); |
| void testme() { Expect.equals(Never, T); } |
| } |
| |
| main() { |
| const a = A<Never>(); |
| a.testme(); |
| } |