1 use thiserror::Error;
2 
3 macro_rules! error_type {
4     ($name:ident, $what:expr) => {
5         // Use #[error("invalid {}", $what)] instead.
6 
7         #[derive(Error, Debug)]
8         #[error(concat!("invalid ", $what))]
9         pub struct $name;
10     };
11 }
12 
13 error_type!(Error, "foo");
14 
main()15 fn main() {}
16