Reduce unsafe code in get_or #63
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get_or() currently works as a wrapper around get_or_try(). It wraps the result of the passed function into a Result<T, ()> and then calls unreachable_unchecked, which is an unsafe function. However, as an Err branch is never instantiated for this Result type, we can use the uninhabited Infallible type instead of the unit type. At this point it is 100% safe to unwrap the underlying result and match on the uninhabited error type to eliminate that branch. It turns out this was the only time that the "unreachable" module was used in the library, so I've also taken the liberty of deleting that file. Signed-off-by: John Nunley <dev@notgull.net>
Amanieu
reviewed
Oct 11, 2023
| @@ -187,9 +186,9 @@ impl<T: Send> ThreadLocal<T> { | |||
| where | |||
| F: FnOnce() -> T, | |||
| { | |||
| unsafe { | |||
| self.get_or_try(|| Ok::<T, ()>(create())) | |||
| .unchecked_unwrap_ok() | |||
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I think you can even eliminate the Err line entirely.
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I get "missing match arm" on the current compiler version. I think you need exhaustive_patterns to land first before that works.
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Test failure is not my fault; |
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Just bump the MSRV in CI to 1.63 so the tests pass. |
Signed-off-by: John Nunley <dev@notgull.net>
Done. |
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Ah, |
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Does bumping the CI version to 1.65 not fix this? |
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It doesn't. I'm going to drop this PR for now as its usefulness is limited |
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get_or() currently works as a wrapper around get_or_try(). It wraps the result of the passed function into a Result<T, ()> and then calls unreachable_unchecked, which is an unsafe function. However, as an Err branch is never instantiated for this Result type, we can use the uninhabited Infallible type instead of the unit type. At this point it is 100% safe to unwrap the underlying result and match on the uninhabited error type to eliminate that branch.
It turns out this was the only time that the "unreachable" module was used in the library, so I've also taken the liberty of deleting that file.