mirror of https://github.com/rust-lang/rust
50 lines
942 B
Rust
50 lines
942 B
Rust
//@check-pass
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use higher_kinded_types::*;
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mod higher_kinded_types {
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pub(crate) trait HKT {
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type Of<'lt>;
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}
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pub(crate) trait WithLifetime<'lt> {
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type T;
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}
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impl<T: ?Sized + for<'any> WithLifetime<'any>> HKT for T {
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type Of<'lt> = <T as WithLifetime<'lt>>::T;
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}
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}
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trait Trait {
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type Gat<'lt>;
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}
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impl Trait for () {
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type Gat<'lt> = ();
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}
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/// Same as `Trait`, but using HKTs rather than GATs
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trait HTrait {
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type Hat: ?Sized + HKT;
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}
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impl<T: Trait> HTrait for T {
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type Hat = dyn for<'lt> WithLifetime<'lt, T = T::Gat<'lt>>;
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}
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impl<Hat: ?Sized + HKT> Trait for Box<dyn '_ + HTrait<Hat = Hat>> {
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type Gat<'lt> = Hat::Of<'lt>;
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}
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fn existential() -> impl for<'a> Trait<Gat<'a> = ()> {}
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fn dyn_hoops<T: Trait>(
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_: T,
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) -> Box<dyn HTrait<Hat = dyn for<'a> WithLifetime<'a, T = T::Gat<'a>>>> {
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loop {}
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}
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fn main() {
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let _ = || -> _ { dyn_hoops(existential()) };
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}
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