Implement RFC 2707 + Parser recovery for range patterns
Implement https://github.com/rust-lang/rfcs/pull/2707.
- Add a new basic syntactic pattern form `ast::PatKind::Rest` (parsed as `..` or `DOTDOT`) and simplify `ast::PatKind::{Slice, Tuple, TupleStruct}` as a result.
- Lower `ast::PatKind::Rest` in combination with the aforementioned `PatKind` variants as well as `PatKind::Ident`. The HIR remains unchanged for now (may be advisable to make slight adjustments later).
- Refactor `parser.rs` wrt. parsing sequences and lists of things in the process.
- Add parser recovery for range patterns of form `X..`, `X..=`, `X...`, `..Y`, `..=Y`, and `...Y`.
This should make it easy to actually support these patterns semantically later if we so desire.
cc https://github.com/rust-lang/rust/issues/62254
r? @petrochenkov
Break dependencies between `syntax_ext` and other crates
Move `source_util` macros into `syntax_ext`.
Move other early code generation facilities like standard library injection into `syntax_ext`.
The only crate that depends on `syntax_ext` now is `rustc_interface` which is one of the "final" crates that depend on everything.
Minor: Cleanup dependencies of `rustc_driver`, many of them are no longer used after introduction of `rustc_interface`.
r? @eddyb
Define built-in macros through libcore
This PR defines built-in macros through libcore using a scheme similar to lang items (attribute `#[rustc_builtin_macro]`).
All the macro properties (stability, visibility, etc.) are taken from the source code in libcore, with exception of the expander function transforming input tokens/AST into output tokens/AST, which is still provided by the compiler.
The macros are made available to user code through the standard library prelude (`{core,std}::prelude::v1`), so they are still always in scope.
As a result **built-in macros now have stable absolute addresses in the library**, like `core::prelude::v1::line!()`, this is an insta-stable change.
Right now `prelude::v1` is the only publicly available absolute address for these macros, but eventually they can be moved into more appropriate locations with library team approval (e.g. `Clone` derive -> `core::clone::Clone`).
Now when built-in macros have canonical definitions they can be imported or reexported without issues (https://github.com/rust-lang/rust/issues/61687).
Other changes:
- You can now define a derive macro with a name matching one of the built-in derives (https://github.com/rust-lang/rust/issues/52269). This was an artificial restriction that could be worked around with import renaming anyway.
Known regressions:
- Empty library crate with a crate-level `#![test]` attribute no longer compiles without `--test`. Previously it didn't compile *with* `--test` or with the bin crate type.
Fixes https://github.com/rust-lang/rust/issues/61687
Fixes https://github.com/rust-lang/rust/issues/61804
r? @eddyb
Implement slow-path for FirstSets::first
When 2 or more sequences share the same span, we can't use the precomputed map
for their first set. So we compute it recursively.
Fixes#62831.
