Suppress warning about #require(nonOptional) in some cases.#947
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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.
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@swift-ci test |
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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
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Feb 11, 2025
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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
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Feb 11, 2025
grynspan
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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
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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
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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: