Macro enum_derive_2018::EnumInnerAsTrait

macro_rules! EnumInnerAsTrait {
    ($arg:tt $vis:vis enum $name:ident { $($body:tt)* }) => { ... };
}

Derives a method for an unary enum returning a borrowed pointer to the inner value, cast to a trait object.

EnumInnerAsTrait! accepts a single deriving form that specifies the name of the method to be derived, whether the borrow should be mutable, and the trait of interest. For example:

macro_attr! {
    #[derive(EnumInnerAsTrait!(pub as_display -> &dyn std::fmt::Display))]
    enum Value {
        U32(u32),
        U64(u64),
    }
}

let s = format!("{}", Value::U64(42).as_display());
assert_eq!(&s[..], "42");