Subenum is a simple proc-macro to derive subsets of enums. It allows conversion
between the parent and the child, will derive any traits on the child that you
have on the parent, and will implement PartialEq
between the parent and child
if you derive it on the parent.
I think the simplest way to explain it is with an example:
use subenum::subenum;
#[subenum(Edible)]
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum Plant {
#[subenum(Edible)]
Basil,
#[subenum(Edible)]
Tomato,
Manzanita,
Pine,
}
fn main() -> Result<(), EdibleConvertError> {
let plant = Plant::Tomato;
// We can convert between them.
let edible = Edible::try_from(plant)?;
let _plant2 = Plant::from(edible);
// We can compare them.
assert_eq!(plant, edible);
// We derive anything that's derived on the parent, such as clone.
let edible2 = edible.clone();
Ok(())
}
In addition to simple enums and built-in traits, subenum
works with complex
enums and third-party attributes.
use subenum::subenum;
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum AppleType {
CosmicCrisp,
Fuji,
PinkLady,
}
#[subenum(Foo, Tree, Edible, Grass)]
#[derive(Debug, Clone, Copy, PartialEq, strum::Display)]
pub enum Plant<'a, T> {
#[subenum(Foo)]
#[strum(serialize = "This is not a plant!")]
Foo { x: i32, y: i32 },
#[subenum(Tree, Edible)]
Apple(AppleType),
#[subenum(Grass)]
Bamboo(&'a str),
#[subenum(Edible)]
Basil(T),
#[subenum(Tree)]
Fir,
#[subenum(Tree)]
Pine,
#[subenum(Edible)]
Tomato,
#[subenum(Edible, Grass)]
Wheat,
}
fn main() -> Result<(), TreeConvertError> {
let plant: Plant<'_, u32> = Plant::Apple(AppleType::CosmicCrisp);
let tree = Tree::try_from(plant)?;
assert_eq!(plant, tree);
let tree2 = tree.clone();
assert_eq!(tree2.to_string(), "Apple");
let foo = Foo::Foo { x: 3, y: 4 };
assert_eq!(foo.to_string(), "This is not a plant!");
let edible = Edible::Basil(3);
let plant = Plant::from(edible);
assert_eq!(plant.to_string(), "Basil");
// Can't compare two subenums.
// assert_ne!(tree2, edible);
// But we can do some conversion-trickery
assert_ne!(Plant::from(tree2), Plant::from(edible));
Ok(())
}
Maybe you have an enum that can't be Copy
d, but the subenum can, and you want
to derive it:
use subenum::subenum;
#[subenum(Bar, Qux(derive(Copy)))]
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum Foo {
#[subenum(Bar)]
A(String),
#[subenum(Qux)]
B,
#[subenum(Bar, Qux)]
C(u8),
}
fn main() {
let b = Qux::B;
let c = b;
assert_eq!(b, c);
}
Bound lifetimes (e.g. for<'a, 'b, 'c>
) are not currently supported. Please
open a ticket if these are desired.
default
-std
anderror_trait
std
- Use standard library collections and allocators within this proc macroerror_trait
- ImplementError
forConvertError
types.- When combined with nightly and
#![feature(error_in_core)]
supports#[no_std]
- Otherwise, this feature requires
std
as well.
- When combined with nightly and