Suppress warning about #require(nonOptional) in some cases. #947
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
When using `try #require()` to unwrap an optional value, we emit a compile-time warning if the value is not actually optional. However, there is a bug in the type checker (swiftlang/swift#79202) that triggers a false positive when downcasting an object (of `class` type), e.g.: ```swift class Animal {} class Duck: Animal {} let beast: Animal = Duck() let definitelyADuck = try #require(beast as? Duck) //⚠️ '#require(_:_:)' is redundant because 'beast as? Duck' never equals 'nil' ``` This change suppresses the warning we emit if the expression contains certain syntax tokens (namely `?`, `nil`, or `Optional`) on the assumption that their presence means the test author is expecting an optional value and we've hit a false positive.
grynspan added bug grynspan requested review from SeanROlszewski, briancroom, stmontgomery and suzannaratcliff as code owners 
| @swift-ci test |
| Is there an additional test you could add which would be an expected failure right now, but pass once swiftlang/swift#79202 is resolved? |
briancroom approved these changes Feb 11, 2025
No, because I don't have a way to trigger the mismatch except during macro expansion, which is faked (different macro overloads get different names.) |
briancroom approved these changes Feb 11, 2025
grynspan deleted the jgrynspan/suppress-non-optional-warning-sometimes branch grynspan added a commit that referenced this pull request Feb 11, 2025
When using `try #require()` to unwrap an optional value, we emit a compile-time warning if the value is not actually optional. However, there is a bug in the type checker (swiftlang/swift#79202) that triggers a false positive when downcasting an object (of `class` type), e.g.: ```swift class Animal {} class Duck: Animal {} let beast: Animal = Duck() let definitelyADuck = try #require(beast as? Duck) //⚠️ '#require(_:_:)' is redundant because 'beast as? Duck' never equals 'nil' ``` This change suppresses the warning we emit if the expression contains certain syntax tokens (namely `?`, `nil`, or `Optional`) on the assumption that their presence means the test author is expecting an optional value and we've hit a false positive. ### Checklist: - [x] Code and documentation should follow the style of the [Style Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md). - [x] If public symbols are renamed or modified, DocC references should be updated.
grynspan added a commit that referenced this pull request Feb 11, 2025
…949) - **Explanation**: Suppress some warnings that occur due to swiftlang/swift#79202 when the compiler selects the wrong overload of `try #require()` for expansion. - **Scope**: Tests using `try #require()` with reference types. - **Issues**: works around swiftlang/swift#79202 - **Original PRs**: #947 - **Risk**: Low, just suppresses some warnings we generate (lack of these warnings is not harmful) - **Testing**: Added a unit test - **Reviewers**: @briancroom
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit. This suggestion is invalid because no changes were made to the code. Suggestions cannot be applied while the pull request is closed. Suggestions cannot be applied while viewing a subset of changes. Only one suggestion per line can be applied in a batch. Add this suggestion to a batch that can be applied as a single commit. Applying suggestions on deleted lines is not supported. You must change the existing code in this line in order to create a valid suggestion. Outdated suggestions cannot be applied. This suggestion has been applied or marked resolved. Suggestions cannot be applied from pending reviews. Suggestions cannot be applied on multi-line comments. Suggestions cannot be applied while the pull request is queued to merge. Suggestion cannot be applied right now. Please check back later.
When using
try #require()to unwrap an optional value, we emit a compile-time warning if the value is not actually optional. However, there is a bug in the type checker (swiftlang/swift#79202) that triggers a false positive when downcasting an object (ofclasstype), e.g.:This change suppresses the warning we emit if the expression contains certain syntax tokens (namely
?,nil, orOptional) on the assumption that their presence means the test author is expecting an optional value and we've hit a false positive.Checklist: