What problem are you trying to solve?

It'd be helpful if the infra spec section on algorithm parameters mentioned how to have a parameter have two types (for instance, a type or failure, or a type and string). It seems like this is somewhat common

What solutions exist today?

It's possible to pass in two optional parameters and have the caller only set one of them, although it's less immediately clear that the two are mutually exclusive.

How would you solve it?

No response

Anything else?

No response