09e3989758
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
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| .. | ||
| attr | ||
| diagnostics | ||
| ext | ||
| parse | ||
| util | ||
| ast.rs | ||
| build.rs | ||
| Cargo.toml | ||
| config.rs | ||
| early_buffered_lints.rs | ||
| entry.rs | ||
| error_codes.rs | ||
| feature_gate.rs | ||
| json.rs | ||
| lib.rs | ||
| mut_visit.rs | ||
| ptr.rs | ||
| README.md | ||
| show_span.rs | ||
| source_map.rs | ||
| std_inject.rs | ||
| test.rs | ||
| test_snippet.rs | ||
| tokenstream.rs | ||
| visit.rs | ||
The syntax crate contains those things concerned purely with syntax
– that is, the AST ("abstract syntax tree"), parser, pretty-printer,
lexer, macro expander, and utilities for traversing ASTs.
For more information about how these things work in rustc, see the rustc guide: