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Auto merge of rust-lang#135057 - compiler-errors:project-unconstrained, r=<try>
Project to `TyKind::Error` when there are unconstrained non-lifetime (ty/const) impl params
I think this is a bit less invasive of an approach compared to rust-lang#127973.
It splits the `enforce_impl_params_are_constrained` function into lifetime/non-lifetime, and queryfies the latter. We can then use the result of the latter query (`Result<(), ErrorGuaranteed>`) to intercept projection and constrain the projected type to `TyKind::Error`, which ensures that we leak no ty or const vars to places that don't expect them, like `normalize_erasing_regions`.
The reason we split `enforce_impl_params_are_constrained` into two parts is because we only error for *lifetimes* if the lifetime ends up showing up in any of the associated types of the impl (e.g. we allow `impl<'a> Foo { type Assoc = (); }`). However, in order to compute the `type_of` query for the anonymous associated type of an RPITIT, we need to do trait solving (in `query collect_return_position_impl_trait_in_trait_tys`). That would induce cycles. Luckily, it turns out for lifetimes we don't even care about if they're unconstrained, since they're erased in all contexts that we are trying to fix ICEs. So it's sufficient to keep this check separated out of the query.
Fixesrust-lang#123141Fixesrust-lang#125874Fixesrust-lang#126942Fixesrust-lang#127804Fixesrust-lang#130967
r? oli-obk
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