Don't capture arguments to #expect(exitsWith:) during macro expansion. #912
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Other than the body closure, the arguments to `#expect(exitsWith:)` are not guaranteed to be literals or otherwise context-free, but we capture them during macro expansion. This can result in obscure errors if the developer writes an exit test with an argument that is computed: ```swift let foo = ... await #expect(exitsWith: self.exitCondition(for: foo)) { // 🛑 error: closure captures 'foo' before it is declared // 🛑 error: enum declaration cannot close over value 'self' defined in outer scope // (and other possible errors) ... } ``` This PR removes the macro's compile-time dependency on its `exitCondition` and `sourceLocation` arguments and introduces an `ID` type to identify exit tests (instead of using their source locations as unique IDs.) The `ID` type is meant to be a UUID, but for the moment I've just strung together two 64-bit integers instead to avoid a dependency on Foundation or platform API. 
grynspan added bug grynspan requested review from SeanROlszewski, briancroom, stmontgomery and suzannaratcliff as code owners 
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stmontgomery approved these changes Jan 15, 2025
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Other than the body closure, the arguments to
#expect(exitsWith:)are not guaranteed to be literals or otherwise context-free, but we capture them during macro expansion. This can result in obscure errors if the developer writes an exit test with an argument that is computed:This PR removes the macro's compile-time dependency on its
exitConditionandsourceLocationarguments and introduces anIDtype to identify exit tests (instead of using their source locations as unique IDs.) TheIDtype is meant to be a UUID, but for the moment I've just strung together two 64-bit integers instead to avoid a dependency on Foundation or platform API.Checklist: