First Draft: Callback For Matching Type

[Dom DiSc]

On Wednesday, 26 June 2024 at 17:14:24 UTC, Quirin Schroll wrote:
> I now have implemented a `SumType` that is commutative, 
> associative, and idempotent, that is:
> * the order of types does not matter: `SumType!(T, U)` is the 
> same as `SumType!(U, T)`,
> * they auto-inline like alias sequences: `SumType!(Ts, 
> SumType!Us, SumType!Vs)` is the same as `SumType!(Ts, Us, Vs)`, 
> and
> * duplicates don’t matter: `SumType!(T, T, Ts)` is `SumType!(T, 
> Ts)`.

This is so cool.
I was always sceptical about the usefulness of sumtypes, but with 
these properties I actual like it.