[4.1] Restore a very narrow function argument conversion for -swift-version 4. #14480
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Allow functions with type `(()) -> T` to be passed in places where we expect `() -> T`, but only for -swift-version 4 (for -swift-version 3 this already works due to other horrible things in CSSimplify.cpp). We need to look at how we can help migrate these cases to -swift-version 5, but in the meantime, but that is something we can consider separately. Fixes rdar://problem/36670720 / https://bugs.swift.org/browse/SR-6796 (cherry picked from commit 6310aca)
Move the existing test into Compatibility/tuple_arguments_4.swift. Move the Swift 3 test, Compatibility/tuple_arguments.swift, into Compatibility/tuple_arguments_4.swift. Add a couple new tests to each file to capture what we do in each mode. Overall this doesn't seem like the most satisfying approach for covering compatibility testing in our standard commit testing, but it's all we've got at the moment. (cherry picked from commit 5a02541)
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@swift-ci Please test |
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@swift-ci Please test source compatibility |
rudkx
changed the title
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@swift-ci please nominate |
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Explanation: We broke compatibility with treating function types that take
Voidas an argument as being allowed as arguments to functions expecting function types that take no arguments. We do not want to support this long term, but did up through Swift 4, so we shouldn't break it in Swift 4.1.Scope of Issue: This particular case probably will not effect a large number of users directly, but this affects at least one popular project and could effect the users of that project.
Origination: A change was made to make function types more consistent, to avoid exactly this kind of "emergent behavior".
Risk: The fix here is very targeted, so the risk seems low.
Fixes: rdar://problem/36670720 / https://bugs.swift.org/browse/SR-6796
Reviewed By: @xedin