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Diffstat (limited to '')
-rw-r--r-- | src/test/ui/associated-types/issue-47139-1.rs | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/src/test/ui/associated-types/issue-47139-1.rs b/src/test/ui/associated-types/issue-47139-1.rs new file mode 100644 index 000000000..c55fc3434 --- /dev/null +++ b/src/test/ui/associated-types/issue-47139-1.rs @@ -0,0 +1,78 @@ +// run-pass +// Regression test for issue #47139: +// +// Coherence was encountering an (unnecessary) overflow trying to +// decide if the two impls of dummy overlap. +// +// The overflow went something like: +// +// - `&'a ?T: Insertable` ? +// - let ?T = Option<?U> ? +// - `Option<?U>: Insertable` ? +// - `Option<&'a ?U>: Insertable` ? +// - `&'a ?U: Insertable` ? +// +// While somewhere in the middle, a projection would occur, which +// broke cycle detection. +// +// It turned out that this cycle was being kicked off due to some +// extended diagnostic attempts in coherence, so removing those +// sidestepped the issue for now. + +#![allow(dead_code)] + +pub trait Insertable { + type Values; + + fn values(self) -> Self::Values; +} + +impl<T> Insertable for Option<T> + where + T: Insertable, + T::Values: Default, +{ + type Values = T::Values; + + fn values(self) -> Self::Values { + self.map(Insertable::values).unwrap_or_default() + } +} + +impl<'a, T> Insertable for &'a Option<T> + where + Option<&'a T>: Insertable, +{ + type Values = <Option<&'a T> as Insertable>::Values; + + fn values(self) -> Self::Values { + self.as_ref().values() + } +} + +impl<'a, T> Insertable for &'a [T] +{ + type Values = Self; + + fn values(self) -> Self::Values { + self + } +} + +trait Unimplemented { } + +trait Dummy { } + +struct Foo<T> { t: T } + +impl<'a, U> Dummy for Foo<&'a U> + where &'a U: Insertable +{ +} + +impl<T> Dummy for T + where T: Unimplemented +{ } + +fn main() { +} |