Ability to define 'catch-all' enum variant

[JamesHinshelwood]

It would be beneficial to me to be able to define an extra variant of my enum which is used in the FromStr impl when none of the other variants match.

For example,

#[derive(FromStr)]
enum Fruit {
  #[display("appl")]
  Apple,
  #[display("orng")]
  Orange,
  #[else] // Not sure about naming of this attribute?
  Other(String),
}

If you aren't opposed to the idea, I would like to try adding this feature. Also, if anyone has any good naming ideas that would be appreciated.

[frozenlib]

Can't you use #[display("{0}")] instead, which is still available in the current version?

use parse_display::FromStr;
#[derive(FromStr, Debug)]
enum Fruit {
    #[display("appl")]
    Apple,
    #[display("orng")]
    Orange,
    #[display("{0}")]
    Other(String),
}

let fruit: std::result::Result<Fruit, _> = "unknown".parse();
println!("{:?}", fruit);

This code outputs:

Ok(Other("unknown"))

It can be used in this way because the parsing is done in the following order, but since this order is not documented, I think we need to add documentation and tests for the parsing order.

• Variants without variables(e.g. {0}) in the format string (in order from top to bottom.)
• Variants with variables(e.g. {0}) in the format string (in order from top to bottom.)

If you need to make the variant at the bottom have a higher priority than the variant at the top, I think it would be a good idea to add the ability to specify the priority.