Crate for macro for default enum variant

[KSXGitHub]

Update from moderators: Support for this use case has since been made available through the standard derive(Default) macro since mid-2022, with Rust 1.62.

Original message:

---

I write impl Default for Enum { fn default() -> Self { Enum::DefaultVariant } } for too many times today. I would like a less repetitive code:

#[macro]
enum Enum {
  #[default_variant]
  DefaultVariant,
  Foo,
  Bar,
}

Is there a crate that provide that feature?

[Michael-F-Bryan]

@KSXGitHub

Is there a crate that provide that feature?

Probably not, but it's really easy to write this sort of custom derive yourself.

You could also propose a Default derive for the derive_more crate, which already has a lot of these "utility" derives.

[KSXGitHub]

smart-default provides just what I need.

[daboross]

Took me a bit to write this post, so I missed it. In case you're looking for other options, here are two more:

educe:

#[derive(Educe)]
#[educe(Default)]
enum Enum {
  #[educe(Default)]
  DefaultVariant,
  Foo,
  Bar,
}

defaults:

#[derive(Defaults)]
#[def = "DefaultVariant"]
enum Enum {
  DefaultVariant,
  Foo,
  Bar,
}

(and smart-default, which you found):

#[derive(SmartDefault)]
enum Enum {
  #[default]
  DefaultVariant,
  Foo,
  Bar,
}