Split out the error reporting logic into a separate function
I was trying to read the function and got distracted by the huge block of code in the middle of it. Turns out it only reports diagnostics and all paths within it end in an error. The main function is now more readable imo.
Fix associated type bindings with anon const in GAT position
The first commit formats `type_of.rs`, which is really hard to maintain since it uses a bunch of features like `let`-chains and `if let` match arm bindings. Best if you just review the second two diffs.
Fixes#102333
`Res::SelfTy` currently has two `Option`s. When the second one is `Some`
the first one is never consulted. So we can split it into two variants,
`Res::SelfTyParam` and `Res::SelfTyAlias`, reducing the size of `Res`
from 24 bytes to 12. This then shrinks `hir::Path` and
`hir::PathSegment`, which are the HIR types that take up the most space.
Add `#[rustc_safe_intrinsic]`
This PR adds the `#[rustc_safe_intrinsic]` attribute as mentionned on Zulip. The goal of this attribute is to avoid keeping a list of symbols as the source for stable intrinsics, and instead rely on an attribute. This is similar to `#[rustc_const_stable]` and `#[rustc_const_unstable]`, which among other things, are used to mark the constness of intrinsic functions.
Do not overwrite lifetime binders for another HirId.
This PR makes higher-ranked bounds in where clauses a bit more principled.
We used to conflate `for<'a> T: Trait` with `(for<'a> T): Trait`.
This PR separates both binders.
This caused issued with fn types, which have their own binder, causing us to overwrite the predicates's binders with `fn`'s binders, ICEing.
Fixes https://github.com/rust-lang/rust/issues/98594
Deny associated type bindings within associated type bindings
Fixes#102335
This was made worse by #100865, which unified the way we generate substs for GATs and non-generic associated types. However, the issue was not _caused_ by #100865, evidenced by the test I added for GATs:
```rust
trait T {
type A: S<C<(), i32 = ()> = ()>;
//~^ ERROR associated type bindings are not allowed here
}
trait Q {}
trait S {
type C<T>: Q;
}
fn main() {}
```
^ which passes on beta (where GATs are stable) and presumably ever since GATs support was added to `create_substs_for_associated_item` in astconv.
