Don't special case the `Self` parameter by name
This results in a couple of small diagnostic regressions. They could be avoided by keeping the special case just for diagnostics, but that seems worse.
closes#50125
cc #60869
Revert "Rollup merge of #62696 - chocol4te:fix_#62194, r=estebank"
This reverts commit df21a6f040a7011d509769a61ac7af9502636b33 (#62696), reversing
changes made to cc16d0486933e02237190366de2eb43df2215c11.
That PR makes error messages worse than before, and we couldn't come up with a way of actually making them better, so revert it for now. Any idea for making this error message better is welcome!
Fixes#63145.
r? @estebank
Change opaque type syntax from `existential type` to type alias `impl Trait`
This implements a new feature gate `type_alias_impl_trait` (this is slightly different from the originally proposed feature name, but matches what has been used in discussion since), deprecating the old `existential_types` feature.
The syntax for opaque types has been changed. In addition, the "existential" terminology has been replaced with "opaque", as per previous discussion and the RFC.
This makes partial progress towards implementing https://github.com/rust-lang/rust/issues/63063.
r? @Centril
Use variant names rather than descriptions for identifying desugarings in `#[rustc_on_unimplemented]`.
Both are highly unstable, but variant name is at least a single identifier.
We have to deal with dummy spans anyway
Remove def-site span from expander interfaces.
It's not used by the expansion infra, only by specific expanders, which can keep it themselves if they want it.
create a "provisional cache" to restore performance in the case of cycles
Introduce a "provisional cache" that caches the results of auto trait resolutions but keeps them from entering the *main* cache until everything is ready. This turned out a bit more complex than I hoped, but I don't see another short term fix -- happy to take suggestions! In the meantime, it's very clear we need to rework the trait solver. This resolves the extreme performance slowdown experienced in #60846 -- I plan to add a perf.rust-lang.org regression test to track this.
Caveat: I've not run `x.py test` in full yet.
r? @pnkfelix
cc @arielb1
Fixes#60846
