There are cases where privileging the first alternative makes sense (like Maybe[T] = None|T with None = struct{} e.g.), and there are cases where it doesn't (like Either[L,R] = L|R). There has been an extensive amount of discussion about a number of different proposals, e.g. https://github.com/golang/go/issues/54685, https://github.com/golang/go/issues/57644, etc., but so far, much like "better" error handling, no workable consensus has yet emerged.
Comments
Why not just define default(Foo|Bar) as default(Foo)?
There are cases where privileging the first alternative makes sense (like Maybe[T] = None|T with None = struct{} e.g.), and there are cases where it doesn't (like Either[L,R] = L|R). There has been an extensive amount of discussion about a number of different proposals, e.g. https://github.com/golang/go/issues/54685, https://github.com/golang/go/issues/57644, etc., but so far, much like "better" error handling, no workable consensus has yet emerged.