Skip to content
forked from paholg/subenum

A Rust macro to make enums with a subset of values of the parent

Notifications You must be signed in to change notification settings

Nexelous/subenum

 
 

Folders and files

NameName
Last commit message
Last commit date

Latest commit

 

History

21 Commits
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Repository files navigation

crates.io Build Status docs.rs

subenum

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.

Simple Example

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(())
}

Complex Example

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(())
}

Subenum-specific proc-macros

Maybe you have an enum that can't be Copyd, 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);
}

Limitations

Bound lifetimes (e.g. for<'a, 'b, 'c>) are not currently supported. Please open a ticket if these are desired.

Features

  • default - std and error_trait
  • std - Use standard library collections and allocators within this proc macro
  • error_trait - Implement Error for ConvertError types.

About

A Rust macro to make enums with a subset of values of the parent

Resources

Stars

Watchers

Forks

Releases

No releases published

Packages

No packages published

Languages

  • Rust 100.0%