Correctly block @Suite and @Test on XCTest.XCTest and XCTestSuite.
#1456
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…ite`. This PR ensures that we diagnose if `@Suite` or `@Test` is applied to a class (or method on such class) that subclasses [`XCTest.XCTest`](https://developer.apple.com/documentation/xctest/xctest) or [`XCTestSuite`](https://developer.apple.com/documentation/xctest/xctestsuite), not just [`XCTestCase`](https://developer.apple.com/documentation/xctest/xctestcase). This change also suppresses the emitted call to the helper function `__invokeXCTest[Case]Method()` if the suite type is _known_ not to subclass `XCTest.XCTest` (e.g. because it's a `struct`.) This slightly improves the performance of non-class suite types (although probably not measurably so). Finally, this change improves the emitted diagnostic when `@Test` is used on a method in an `XCTest.XCTest` subclass such that it explicitly states the reason why the attribute can't be used: > 🛑 Attribute 'Test' cannot be applied to a function within class 'C' because it is a subclass of 'XCTest', 'XCTestCase', or 'XCTestSuite'
grynspan
requested review from
briancroom,
jerryjrchen and
stmontgomery
as code owners
grynspan
added
performance
jerryjrchen
approved these changes
Jan 6, 2026
stmontgomery
approved these changes
Jan 6, 2026
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This PR ensures that we diagnose if
@Suiteor@Testis applied to a class (or method on such class) that subclassesXCTest.XCTestorXCTestSuite, not justXCTestCase.This change also suppresses the emitted call to the helper function
__invokeXCTest[Case]Method()if the suite type is known not to subclassXCTest.XCTest(e.g. because it's astruct.) This slightly improves the performance of non-class suite types (although probably not measurably so).Finally, this change improves the emitted diagnostic when
@Testis used on a method in anXCTest.XCTestsubclass such that it explicitly states the reason why the attribute can't be used:Checklist: