examples/dump-syntax/main.rs

//! Parse a Rust source file into a `syn::File` and print out a debug
//! representation of the syntax tree.
//!
//! Use the following command from this directory to test this program by
//! running it on its own source code:
//!
//!     cargo run -- main.rs
//!
//! The output will begin with:
//!
//!     File {
//!         shebang: None,
//!         attrs: [
//!             Attribute {
//!                 pound_token: Pound,
//!                 style: Inner(
//!         ...
//!     }

use std::env;
use std::fs::File;
use std::io::Read;
use std::process;

fn main() {
    let mut args = env::args();
    let _ = args.next(); // executable name

    let filename = match (args.next(), args.next()) {
        (Some(filename), None) => filename,
        _ => {
            eprintln!("Usage: dump-syntax path/to/filename.rs");
            process::exit(1);
        }
    };

    let mut file = File::open(&filename).expect("Unable to open file");

    let mut src = String::new();
    file.read_to_string(&mut src).expect("Unable to read file");

    let syntax = syn::parse_file(&src).expect("Unable to parse file");
    println!("{:#?}", syntax);
}