https://github.com/nrc/proc-macro-rules

Macro-rules-style syntax matching for procedural macros
https://github.com/nrc/proc-macro-rules

macros parsing pattern-matching rust

Last synced: 1 day ago
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Macro-rules-style syntax matching for procedural macros

• Host: GitHub
• URL: https://github.com/nrc/proc-macro-rules
• Owner: nrc
• Created: 2019-01-02T01:16:20.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2023-11-07T03:12:12.000Z (about 1 year ago)
• Last Synced: 2024-11-29T03:51:32.710Z (27 days ago)
• Topics: macros, parsing, pattern-matching, rust
• Language: Rust
• Homepage:
• Size: 43.9 KB
• Stars: 51
• Watchers: 4
• Forks: 5
• Open Issues: 14
• Metadata Files:
  • Readme: README.md

Awesome Lists containing this project

• awesome-rust-list - nrc/proc-macro-rules - macro-rules?style=social"/> : Macro-rules-style syntax matching for procedural macros. (Summary)
• awesome-rust-list - nrc/proc-macro-rules - macro-rules?style=social"/> : Macro-rules-style syntax matching for procedural macros. (Summary)

README

        
# proc-macro-rules

`macro_rules`-style syntax matching for procedural macros.

This crate is work-in-progress, incomplete, and probably buggy!

Example:

```rust

rules!(tokens => {

    ($finish:ident ($($found:ident)*) # [ $($inner:tt)* ] $($rest:tt)*) => {

        for f in found {

            do_something(finish, f, inner, rest[0]);

        }

    }

    (foo $($bar:expr)?) => {

        match bar {

            Some(e) => foo_with_expr(e),

            None => foo_no_expr(),

        }

    }

});

```

## Using proc-macro-rules

Add `proc-macro-rules = "0.3.0"` (or `proc-macro-rules = "0.2.1"` for versions between 1.31 and 1.56) to your Cargo.toml.

Import the `rules` macro with `use proc_macro_rules::rules`, then use with `rules!(tokens => { branches });` where `tokens` is an expression which evaluates to a `TokenStream` (such as the argument in the definition of a procedural macro).

Each branch in `branches` should have the form `( pattern ) => { body }` where `pattern` is a macro-rules-style pattern (using all the same syntax for meta-variables, AST nodes, repetition, etc.) and `body` is rust code executed when the pattern is matched. Within `body`, any meta-variables in the pattern are bound to variables of an appropriate type from either the [proc_macro2](https://github.com/alexcrichton/proc-macro2) or [syn](https://github.com/dtolnay/syn) crates. Where a meta-variable is inside a repetition or option clause, it will be wrapped in a `Vec` or `Option`, respectively.

For example, in the first branch in the above example `ident` has type `syn::Ident` and `inner` has type `Vec`.

## Building and testing

Use `cargo build` to build, `cargo test --all` to test.

## Contributing

Contributions are very welcome! It would be great to know things which are missing or incorrect (in general we should have the same behaviour as `macro_rules`, so anything different is incorrect). Issues, code, docs, tests, and corrections are all welcome.