| // 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 If N is an expression of the form E1.m1(E2), then: |
| /// |
| /// Let before(E1) = before(N) |
| /// Let before(E2) = after(E2) |
| /// Let T be the static return type of the invocation |
| /// If T <: Never then: |
| /// Let null(N) = unreachable(before(N)). |
| /// Let notNull(N) = unreachable(before(N)). |
| /// Otherwise if T <: Null then: |
| /// Let null(N) = before(N). |
| /// Let notNull(N) = unreachable(before(N)). |
| /// Otherwise if T is non-nullable then: |
| /// Let null(N) = before(N). |
| /// Let notNull(N) = unreachable(before(N)). |
| /// Otherwise: |
| /// Let null(N) = promote(x, Null, before(N)) |
| /// Let notNull(N) = promoteToNonNull(x, before(N)) |
| /// |
| /// @description Checks reachability after method call. Test return type T <: Null |
| /// |
| /// @author sgrekhov@unipro.ru |
| /// @issue 41985 |
| |
| // Requirements=nnbd-strong |
| |
| class C { |
| Null m1() => null; |
| } |
| |
| main() { |
| C c = new C(); |
| int i; |
| if (c.m1() == null) { |
| i = 42; // condition is always true therefore `i` must be definitely assigned |
| } |
| i; // It's not an error to read local non-nullable variable if it is definitely assigned |
| } |