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rust/compiler/rustc_ast
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Matthias Krüger 1fd0c71818
Rollup merge of #120221 - compiler-errors:statements-are-not-patterns, r=nnethercote 
Don't make statement nonterminals match pattern nonterminals

Right now, the heuristic we use to check if a token may begin a pattern nonterminal falls back to `may_be_ident`:
ef71f1047e/compiler/rustc_parse/src/parser/nonterminal.rs (L21-L37)

This has the unfortunate side effect that a `stmt` nonterminal eagerly matches against a `pat` nonterminal, leading to a parse error:
```rust
macro_rules! m {
    ($pat:pat) => {};
    ($stmt:stmt) => {};
}

macro_rules! m2 {
    ($stmt:stmt) => {
        m! { $stmt }
    };
}

m2! { let x = 1 }
```

This PR fixes it by more accurately reflecting the set of nonterminals that may begin a pattern nonterminal.

As a side-effect, I modified `Token::can_begin_pattern` to work correctly and used that in `Parser::nonterminal_may_begin_with`.
2024-08-31 10:08:51 +02:00
..
src Rollup merge of #120221 - compiler-errors:statements-are-not-patterns, r=nnethercote 2024-08-31 10:08:51 +02:00
Cargo.toml Split rustc_type_ir to avoid rustc_ast from depending on it 2024-02-27 18:11:23 +00:00
README.md docs(rustc_ast): update crate descriptions 2021-11-02 21:11:17 -05:00

README.md

The rustc_ast crate contains those things concerned purely with syntax – that is, the AST ("abstract syntax tree"), along with some definitions for tokens and token streams, data structures/traits for mutating ASTs, and shared definitions for other AST-related parts of the compiler (like the lexer and macro-expansion).

For more information about how these things work in rustc, see the rustc dev guide: