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//@ check-pass
//@ compile-flags: -Znext-solver
// A regression test for trait-system-refactor-initiative#184.
//
// When adding nested goals we replace aliases with infer vars
// and add `AliasRelate` goals to constrain them. When doing this
// for `NormalizesTo` goals, we then first tries to prove the
// `NormalizesTo` goal and then normalized the nested aliases.
trait Trait<T> {
type Assoc;
}
impl<T, U> Trait<U> for T {
type Assoc = ();
}
trait Id {
type This;
}
impl<T> Id for T {
type This = T;
}
trait Relate<T> {
type Alias;
}
impl<T, U> Relate<U> for T {
type Alias = <T as Trait<<U as Id>::This>>::Assoc;
}
fn guide_me<T: Trait<u32>>() {
// Normalizing `<T as Relate<i32>>::Alias` relates the associated type with an unconstrained
// term. This resulted in a `NormalizesTo(<T as Trait<<U as Id>::This>>::Assoc, ?x)` goal.
// We replace `<i32 as Id>::This` with an infer var `?y`, resulting in the following goals:
// - `NormalizesTo(<T as Trait<?y>::Assoc, ?x)`
// - `AliasRelate(<i32 as Id>::This, ?y)`
//
// When proving the `NormalizesTo` goal first, we incompletely constrain `?y` to `u32`,
// causing an unexpected type mismatch.
let _: <T as Relate<i32>>::Alias;
}
fn main() {}
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