| // 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() { |
| } |