Feature Request: (or How-To) about call a method on Foldable when "T", "U" inherit from same interface

type Foldable[T any, U any] interface { leftValue() T rightValue() U hasLeftValue() bool }

here is the my case:
1: I build a mo.Either base on a if/else, saying Either[A,B], A and B implement same interface C
2: I build a Foldable from the either. but I want to execute same function on the foldable.

right now the API must pass in two method "successFunc" and "failureFunc", for the case i describe seems redundant

by the way, of course, I can use case assert cast A or B to C. and then call the method.

Start with the Foldable[T,U] interface and the mo.Either API described in the issue, then inspect how the successFunc and failureFunc callbacks are currently used. Determine whether supporting one callback for values sharing interface C is intended as an API change or a how-to clarification; the issue names no files or tests, so the expected behavior needs agreement before implementation.