ICE: expected goal term to be fully unconstrained

[lcnr]

#![feature(type_alias_impl_trait)]

trait Id {
    type Assoc;
}
impl<T> Id for T {
    type Assoc = T;
}

type Tait where Tait : Id<Assoc = Tait> = impl Sized;

currently results in

thread 'rustc' panicked at 'expected goal term to be fully unconstrained: NoSolution', compiler/rustc_trait_selection/src/solve/project_goals.rs:129:26
[..]
query stack during panic:
#0 [param_env] computing normalized predicates of `Tait`
#1 [check_well_formed] checking that `Tait` is well-formed
#2 [check_mod_type_wf] checking that types are well-formed in top-level module
#3 [analysis] running analysis passes on this crate

https://rust.godbolt.org/z/8Y75K5Prr

Don't think we have a test for this 🤔 might be related to some overflow issue @compiler-errors previously discovered?

[compiler-errors]

This ICEs currently due to the fact that structurally_relate_tys was not handling weak aliases correctly, which should be fixed in rust-lang/rust#113086.

Not sure how it behaves after that PR.

[lcnr]

needs test and then can be closed