Macro map_err

macro_rules! map_err {
    ($result:expr, |$err:pat_param| $closure:expr) => { ... };
}

An analog to Result::map_err but without a closure.

use macro_map::map_err;

let myresult: Result<&str, &str> = Err("hello");

let mapped = map_err!(myresult, |myerr| 123);

assert_eq!(mapped, Err(123));

Or with postfix-macros:

use macro_map::map_err;
use postfix_macros::postfix_macros;

let myresult: Result<&str, &str> = Err("hello");

postfix_macros! {
  let mapped = myresult.map_err!(|myerr| 123);
}

assert_eq!(mapped, Err(123));