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//@ revisions: old next
//@[next] compile-flags: -Znext-solver
//@ ignore-compare-mode-next-solver (explicit revisions)
//@ check-pass
// case 3 of https://github.com/rust-lang/trait-system-refactor-initiative/issues/8.
#![crate_type = "lib"]
#![allow(unused)]
trait Unnormalizable {
type Assoc;
}
trait Id<T> {
type Id;
}
impl<T, U> Id<U> for T {
type Id = T;
}
struct Inv<T>(*mut T);
fn unconstrained<T>() -> T {
todo!()
}
fn create<T: Unnormalizable, U>(
x: &T,
) -> (Inv<U>, Inv<<<T as Id<U>>::Id as Unnormalizable>::Assoc>) {
todo!()
}
fn foo<T: Unnormalizable>() {
let t = unconstrained();
let (mut u, assoc) = create::<_, _>(&t);
u = assoc;
// Instantiating `?u` with `<<?t as Id<?u>>::Id as Unnormalizable>::Assoc` would
// result in a cyclic type. However, we can still unify these types by first
// normalizing the inner associated type. Emitting an error here would be incomplete.
drop::<T>(t);
}
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