Treat weak alias types more like ADTs when computing implied bounds #122340
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fmease
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| @@ -144,7 +144,7 @@ pub(crate) fn insert_outlives_predicate<'tcx>( | |||
| } | |||
| } | |||
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| fn is_free_region(region: Region<'_>) -> bool { | |||
| fn is_early_bound_region(region: Region<'_>) -> bool { | |||
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Just a drive-by renaming, cc #117908. I don't know why this used the term free (ReLateParam). It should've always been named is_early_bound_region or sth. in that vein.
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| @@ -5,7 +5,6 @@ mod test_lifetime_param { | |||
| fn defining(a: &str) -> Ty<'_> { a } | |||
| fn assert_static<'a: 'static>() {} | |||
| fn test<'a>() where Ty<'a>: 'static { assert_static::<'a>() } | |||
| //~^ ERROR: lifetime may not live long enough | |||
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WeakTy<'co>: 'static now implies 'co: 'static similar to ADTs. Is that fine / sound?
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it is, but we need tests that show that we actually enforce it, too. I don't know if we have any weak alias type tests for that, even if we have old-style type alias tests for it
| @@ -27,7 +26,6 @@ mod test_type_param { | |||
| fn defining<A>(s: A) -> Ty<A> { s } | |||
| fn assert_static<A: 'static>() {} | |||
| fn test<A>() where Ty<A>: 'static { assert_static::<A>() } | |||
| //~^ ERROR: parameter type `A` may not live long enough | |||
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Similarly, WeakTy<Co>: 'static now implies Co: 'static similar to ADTs. Is that acceptable?
fmease
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☔ The latest upstream changes (presumably #113169) made this pull request unmergeable. Please resolve the merge conflicts. |
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@fmease |
For context, we want to treat lazy type aliases / weak alias types just like ADTs when computing implied bounds (#118479, T-lang design meeting 2023-11-09) but the way I've implemented it in #119350, there are some deviations in behavior which this PR eliminates.
I found this oversight while trying to build
allocwith LTAs enabled by default:struct ExtractIfInner<'a, K, V>would no longer build requiring the explicit boundsK: 'aandV: 'a.With this patch, we imply
K: 'a,V: 'ainstead ofAlias<K, V>: 'ain the following code which is consistent with ADTs:Instead of treating weak alias types as abstract when computing the outlives-components like we do for the other kinds of alias types, we shallowly walk their generic args like we do with ADTs.
This is yet another case in a series (#121344, #120780) where weak alias types deviate in behavior from the other kinds of alias types, well... ^^'.
r? @oli-obk