Diagnose when we incorrectly infer the type of a capture list item in an exit test. #1152
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…t test.
This PR adds the ability to infer the type of a parameter of a function or closure that encloses an exit test. For example, `x` here:
```swift
func f(x: Int) async {
await #expect(processExitsWith: .failure) { [x] in
...
}
}
```
This inference still fails if a parameter is shadowed by a variable with an incompatible type; we still need something like `decltype()` to solve for such cases. Still, being able to capture `@Test` function arguments with minimal ceremony is helpful:
```swift
@test(arguments: 0 ..< 100) func f(i: Int) async {
await #expect(exitsWith: .failure) { [i] in
...
}
}
```
grynspan
added
enhancement
grynspan
commented
Jun 13, 2025
|
|
||
| // Diagnose that the type of 'expr' is invalid. | ||
| let name = nameExpr.representedLiteralValue ?? expr.trimmedDescription | ||
| let capture = ClosureCaptureSyntax(name: .identifier(name)) |
There was a problem hiding this comment.
This fake ClosureCaptureSyntax instance is created because we can't pass such a thing as an expression and we need to use a string instead. It's a temporary abstraction until swiftlang/swift-syntax#3085 is resolved.
grynspan
requested review from
stmontgomery,
briancroom and
suzannaratcliff
as code owners
|
@swift-ci test |
suzannaratcliff
approved these changes
Jun 18, 2025
|
@swift-ci test |
grynspan
added
the
exit-test-capture-lists
|
Preemptively merging before all CI is complete as it passed previously and is passing now on Linux. Windows and Mac CI are stuck waiting. |
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Follow-up to #1130, split out for clarity.
This PR adds a custom diagnostic at compile time if we incorrectly infer the type of a captured function argument or
selfin an exit test. For example:This improves our feedback to the developer when we encounter a pattern like that. The developer will now see:
Checklist: