MonadicAST

A collection of Rust abstract syntax tree transformations, which target unidiomatic (and possibly unsafe!) code constructs that appear in Rust code generated by C-to-Rust code generators, e.g. https://c2rust.com/.

This library provides an API to analyze and transform Rust source code, or even its underlying AST, as represented by a syn::File object. (See https://crates.io/crates/syn for more information about the crate::syn parsing library.)

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Usage:

The monadicast library exposes a public MonadicAst struct, which can be constructed from a string of Rust source code with its constructor or from the syn::File AST itself.

With a given MonadicAst, one can

• obtain its held AST, consuming the struct: MonadicAst::ast(),
• obtain a string representing the formatted source code corresponding to the AST: MonadicAst::result(),
• apply a transformation to the held AST, e.g. MonadicAst::convert_ffi_types().

use monadicast::MonadicAst;
use std::error::Error;
use std::fs;

fn main() -> Result<(), Box<dyn Error>> {
    let content = fs::read_to_string("./example/input.rs")?;
    let output = MonadicAst::new(&content)?
        // apply some transformations to the AST...
        .convert_ffi_types()
        .replace_raw_pointers()
        .translate_while_to_for_loops()
        // ...and finally convert the AST back to a source code string
        .result();
    
    fs::write("./example/output.rs", output)?;
    Ok(())
}

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Note: If you couldn't tell from the name, this library imposes a monadic structure around the syn::File abstract syntax tree datatype. If you are familiar with monads, the conventional unit is the From<syn::File> method and each AST transformation is a bind (>>=) on the MonadicAst struct.

If you aren't familiar with monads, check out this stack overflow post and/or this blog post about them. There is also more complete documentation in the source code, which can be found by reading the RustDoc in src/monad/ast.rs.