Derive Macro DeepVariants 

#[derive(DeepVariants)]
{
    // Attributes available to this derive:
    #[ancestors]
    #[enum_tree]
}

Create a const array with all possible values of an enum. Target must be an enum, and each variant of the target must be of nested unit type. A variant is of nested unit type if it is either:

a) a unit variant, or b) an singleton tuple variant, whose inner type is compatible.

Variants annotated with #[enum_tree(skip)] are excluded.