From for unit enum variants

[spearman]

It seems like in the change from version 0.99 to version 1.0 that unit enum variants no longer implement from unit () by default.

For example:

#[derive(From)]
enum Myenum {
  Null,
  Bool(bool),
  Num(i32),
  Text(String)
}

Only implements From<bool>, From<i32> and From<String>, whereas before it would also implement From<()>. I tried adding the #[from] attribute to the unit variant, but then it doesn't implement From for any of the other variants, so they also need to #[from] attribute so I end up with:

#[derive(From)]
enum Myenum {
  #[from] Null,
  #[from] Bool(bool),
  #[from] Num(i32),
  #[from] Text(String)
}

Is there a better way to do this?

[JelteF]

Yeah, this these derives for () were removed by default as the feature was considered pretty useless: #106

What did you use it for?

[JelteF]

Regarding the easiest to maintain solution: Depending on how many times you need this, it be just be the easiest to implement the From implementation for () yourself manually.

[sjunepark]

Manual implementation is not hard, but in my case, I wanted to achieve something like Display

#[derive(Display)]
#[display("{_variant}")]
enum Inner {
    Y,
    K,
    N,
    E,
}

I'm not sure if allowing From to handle unit variants will be appropriate, but at least an error would have been nice. (For example, if I try to derive an AsRef on a enum, it errors.)
Applying From when there are unit variants show no errors at all, and I found out nothing was being created when using cargo expand

[spearman]

Yeah, this these derives for () were removed by default as the feature was considered pretty useless: #106

What did you use it for?

I looked at where I was using it and really the only advantage is that it's usually shorter to type ().into() than to type out the full enum variant (and path to bring it into scope). On the other hand it's a bit less clear so I think I prefer giving the name of the enum. I've actually removed it from my code now so it's no longer an issue for me. You can close this if you want.

[JelteF]

@sjunepark You can use FromStr for the exact conversion you're describing.

@spearman thank you, then I'll close this issue.