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rustrust-cargo

How to get cargo-expand to expand macros within macros

I'm learning Rust and am trying to use cargo-expand on the default Hello, World program. From what I understand it's supposed to expand all the macros, but when I use it, it leaves in a macro that another macro generates.

#![feature(prelude_import)]
#[prelude_import]
use std::prelude::rust_2021::*;
#[macro_use]
extern crate std;
fn main() {
    {
        ::std::io::_print(format_args!("Hello, World\n"));
    };
}

From what I understood, the output of cargo expand should expand everything, so I'm a little confused. I tried googling and searching for an answer but everything I read showed no macros within the output.

Is this right or not?

Solution

  • If you mean the format_args!, I'll quote dtolnay (the cargo-expand maintainer) from this issue:

    This is working correctly. format_args does not expand to Rust code. (In the past it used to.)

    Cargo-expand does recursively expand macros. Just in this case it can't.