54 lines
1.2 KiB
Rust
54 lines
1.2 KiB
Rust
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// check-fail
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// known-bug: #90950
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trait Yokeable<'a>: 'static {
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type Output: 'a;
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}
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trait IsCovariant<'a> {}
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struct Yoke<Y: for<'a> Yokeable<'a>> {
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data: Y,
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}
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// impl<Y: for<'a> Yokeable<'a>> Yoke<Y> {
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// fn project<Y2: for<'a> Yokeable<'a>>(
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// &self,
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// f: for<'a> fn(<Y as Yokeable<'a>>::Output, &'a (),
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// ) -> <Y2 as Yokeable<'a>>::Output) -> Yoke<Y2> {
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// unimplemented!()
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// }
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// }
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fn upcast<Y>(x: Yoke<Y>) -> Yoke<Box<dyn IsCovariant<'static> + 'static>> where
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Y: for<'a> Yokeable<'a>,
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for<'a> <Y as Yokeable<'a>>::Output: IsCovariant<'a>
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{
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// x.project(|data, _| {
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// Box::new(data)
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// })
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unimplemented!()
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}
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impl<'a> Yokeable<'a> for Box<dyn IsCovariant<'static> + 'static> {
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type Output = Box<dyn IsCovariant<'a> + 'a>;
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}
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// this impl is mostly an example and unnecessary for the pure repro
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use std::borrow::*;
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impl<'a, T: ToOwned + ?Sized> Yokeable<'a> for Cow<'static, T> {
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type Output = Cow<'a, T>;
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}
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impl<'a, T: ToOwned + ?Sized> IsCovariant<'a> for Cow<'a, T> {}
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fn upcast_yoke(y: Yoke<Cow<'static, str>>) -> Yoke<Box<dyn IsCovariant<'static> + 'static>> {
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upcast(y)
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}
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fn main() {}
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