3 ms·

> the "strum" crate, which has a macro to produce another (plain) enum, but having the discriminant type be named "std::mem::Discriminant<T>" I don't understan

• yakubin 5y ago
  You cut out the rest of the sentence, which is needed to make sense of it. What I mean is, with the "strum" crate I can use a proc macro to automatically generate an "EnumDiscriminant" enum for an "Enum" enum, where "Enum" is defined as: enum Enum { A(u32), B, } and "EnumDiscriminant" is defined as: enum EnumDiscriminant { A, B, } However, the only thing linking those two is a naming convention. I would like to have a universal name for such discriminants. The Rust standard library already has such a discriminant type for any enum - mem::Discriminant<T>, where T is the enum type. However, in order to get the discriminant of Enum::A(5) I need to write mem::discriminant(Enum::A(5)), which introduces noise (especially with bigger tuples or structs) - this 5 here is irrelevant. The mem::discriminant() function is useful for contexts where I have a variable of type Enum and want to get its discriminant, but when I just want to pick a particular discriminant, it's too noisy. I would like to be able to name the discriminant directly. I.e. I would like the standard library type Discriminant<T> be defined for each enum the same way EnumDiscriminant above is defined for Enum. So I could just write Discriminant::<Enum>::A.