syntax: fix dropping of attribute on first param of non-method assocated fn
Fixes#64682.
The general idea is that we bake parsing of `self` into `parse_param_general` and then we just use standard list parsing. Overall, this simplifies the parsing and makes it more consistent.
r? @petrochenkov cc @c410-f3r
Propagate spans and attributes from proc macro definitions
Thanks to https://github.com/rust-lang/rust/pull/63269 we now have spans and attributes from proc macro definitions available in metadata.
However, that PR didn't actually put them into use! This PR finishes that work.
Attributes `rustc_macro_transparency`, `allow_internal_unstable`, `allow_internal_unsafe`, `local_inner_macros`, `rustc_builtin_macro`, `stable`, `unstable`, `rustc_deprecated`, `deprecated` now have effect when applied to proc macro definition functions.
From those attributes only `deprecated` is both stable and supposed to be used in new code.
(`#![staged_api]` still cannot be used in proc macro crates for unrelated reasons though.)
`Span::def_site` from the proc macro API now returns the correct location of the proc macro definition.
Also, I made a mistake in https://github.com/rust-lang/rust/pull/63269#discussion_r312702919, loaded proc macros didn't actually use the resolver cache.
This PR fixes the caching issue, now proc macros go through the `Resolver::macro_map` cache as well.
(Also, the first commit turns `proc_macro::quote` into a regular built-in macro to reduce the number of places where `SyntaxExtension`s need to be manually created.)
Rename `ItemKind::Ty` to `ItemKind::TyAlias`
The current name is not entirely clear without context and `TyAlias` is consistent with `ItemKind::TraitAlias`.
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
