higher-ranked opaque type goals are scuffed

[lcnr]

#![feature(type_alias_impl_trait)]
type Tait<'a> = impl Sized;

fn prove()
where
    for<'a> Tait<'a>: Sized,
{}

#[define_opaque(Tait)]
fn foo<'a>() -> &'a Tait<'a> {
    prove();
    &()
}
fn main() {}

results in

error: internal compiler error: unexpected cyclic definition of `Tait::{opaque#0}`
  --> src/main.rs:11:5
   |
11 |     prove();
   |     ^^^^^^^
   |
note: delayed at compiler/rustc_hir_typeck/src/opaque_types.rs:239:24 - disabled backtrace
  --> src/main.rs:11:5
   |
11 |     prove();
   |     ^^^^^^^

it shouldn't xd

The issue is that each time we prove for<'a> Tait<'a>: Sized we add a new use of Tait<!aN> to the opaque types storage, cc #204 and #220