Macro enum_iter

macro_rules! enum_iter {
    (@all_array_impl,
         $vis:vis,
         ~const_array($all_array:ident)
         $($variant:ident)*
    ) => { ... };
    (@all_array_impl,
         $vis:vis,
         ~const_array($all_array:ident)
         $($variant:ident $((
             $nested_enum:ty
         ))?)*
    ) => { ... };
    (@all_array_impl,
         $vis:vis,
         $($variant:ident $((
                 $nested_enum:ty
         ))?)*
    ) => { ... };
    (@add_variant_impl, $buff:ident, $variant:ident $nested_enum:ty) => { ... };
    (@add_variant_impl, $buff:ident, $variant:ident) => { ... };
    (
        $(~const_array($all_array:ident))?
        $( #[ $enum_attr:meta ] )*
        $vis:vis enum $enum_name:ident {
            $(
                $( #[ $variant_attr:meta ] )*
                $variant:ident $(($nested_enum:ty))? $(= $idx:literal)?
            ),* $(,)?
        }
    ) => { ... };
}

strum::EnumIter alternative that supports nested enums

Implements following items:

• NUM_KINDS associated constant, number of defined kinds.
• iter function, returns the iterator of all possible variants, including ones from the nested variants.

If you use ~const_array prefix, you can also generate ALL constant, which has a constant array of all possible values, but only available for simple enums.

Example

enum_iter! {
    ~const_array(ALL)
    #[derive(Eq, PartialEq, Debug)]
    enum Shade {
        Good,
        Meh,
        Bad,
    }
}

enum_iter! {
    #[derive(Debug, Eq, PartialEq)]
    #[repr(u8)]
    enum Color {
        Green = 1,
        Red(Shade) = 2,
        Blue = 3,
    }
}
assert_eq!(Shade::NUM_KINDS, 3);

const ALL_SHADES: [Shade; Shade::NUM_KINDS] = Shade::ALL;
assert_eq!(ALL_SHADES, [Shade::Good, Shade::Meh, Shade::Bad]);

let results: Vec<_> = Shade::iter().collect();
assert_eq!(results, vec![Shade::Good, Shade::Meh, Shade::Bad]);

let results: Vec<_> = Color::iter().collect();
assert_eq!(results, vec![
    Color::Green,
    Color::Red(Shade::Good),
    Color::Red(Shade::Meh),
    Color::Red(Shade::Bad),
    Color::Blue,
]);