Macro nom::fix_error

macro_rules! fix_error {
    ($i:expr, $t:ty, $submac:ident!( $($args:tt)* )) => { ... };
    ($i:expr, $t:ty, $f:expr) => { ... };
}

translate parser result from IResult<I,O,u32> to IResult<I,O,E> with a custom type

    // will add a Custom(42) error to the error chain
    named!(err_test, add_return_error!(ErrorKind::Custom(42), tag!("abcd")));
    // Convert to IREsult<&[u8], &[u8], &str>
    named!(parser<&[u8], &[u8], &str>, add_return_error!(ErrorKind::Custom("custom error message"), fix_error!(&str, err_test)));

    let a = &b"efghblah"[..];
    let res_a = parser(a);
    assert_eq!(res_a,  Error(error_node_position!( ErrorKind::Custom("custom error message"), a, Position(ErrorKind::Fix, a))));