Use spans pointing at the inside of a rustdoc attribute
Follow up to #51111.
Point to the link in a rustdoc attribute where intralink resolution failed, instead of the full rustdoc attribute's span.
r? @GuillaumeGomez cc @kennytm
The Great Generics Generalisation: Ty Edition
Part of the generic parameter refactoring effort, split off from https://github.com/rust-lang/rust/pull/48149. Contains the `ty`-relative refactoring.
r? @eddyb
This leads to a lot of simplifications, as most code doesn't actually need to know about the specific lifetime/type data; rather, it's concerned with properties like name, index and def_id.
Optimize layout of TypeVariants
This makes references to `Slice` use thin pointers by storing the slice length in the slice itself. `GeneratorInterior` is replaced by storing the movability of generators in `TyGenerator` and the interior witness is stored in `GeneratorSubsts` (which is just a wrapper around `&'tcx Substs`, like `ClosureSubsts`). Finally the fields of `TypeAndMut` is stored inline in `TyRef`. These changes combine to reduce `TypeVariants` from 48 bytes to 24 bytes on x86_64.
r? @michaelwoerister
Refactor auto trait handling in librustdoc to be accessible from librustc.
These commits transfer some of the functionality introduced in https://github.com/rust-lang/rust/pull/47833 to librustc with the intention of making the tools to work with auto traits accessible to third-party code, for example [rust-semverver](https://github.com/rust-lang-nursery/rust-semverver).
Some rough edges remain, and I'm certain some of the FIXMEs introduced will need some discussion, most notably the fairly ugly overall approach to pull out the core logic into librustc, which was previously fairly tightly coupled with various bits and bobs from librustdoc.
cc @Aaron1011
rustdoc: Resolve nested `impl Trait`s
Fixes#50358.
Populates `cx.impl_trait_bounds` incrementally while `clean`ing generic params, so that a synthetic type-parameter can refer to previous ones.
cc #50366
