5 releases
0.1.2 | Jul 18, 2023 |
---|---|
0.1.1 | Jun 4, 2022 |
0.1.0 | Jun 4, 2022 |
0.0.2 | May 29, 2022 |
0.0.1 | May 29, 2022 |
#15 in #discriminant
6KB
discrim
Construct enum variants from their discriminant
NOTE: I'm no longer maintaining this due to the existence of soccer
; I've pretty much absorbed what I built here into that new crate, which I'll be maintaining from now on. If this crate looks interesting to you, you should go use soccer
instead (it's better, I promise).
Overview
In order to initialize certain enum values from their discriminant, you basically have to manually write a giant match block that maps from each discriminant to the corresponding variant. This is both an annoyingly manual process and a potentially unsafe one; for example, what if you forget to update a discriminant value in the match after changing it in the enum definition?
This crate addresses that by providing a way to automatically generate that initialization code. More specifically, for fieldless, non-generic enums with a #[repr(...)]
specified, it provides the FromDiscriminant
trait and corresponding derive macro that automatically generates the initialization code as an implementation of the trait.
This project is licensed under the MIT License.
Example
A simple example, based on the use case that inspired this crate to begin with:
use discrim::FromDiscriminant;
#[derive(Debug, FromDiscriminant)]
#[repr(u8)]
enum Opcode {
Add, Sub, Mul, Div,
}
fn main() {
// prints "Ok(Mul)"
println!("{:?}", Opcode::from_discriminant(2));
// prints "Err(5)"
println!("{:?}", Opcode::from_discriminant(5));
}
Dependencies
~1.5MB
~37K SLoC