The valueOrError has <U extends T>, why?

[witoldsz]

I try to extract the value inside Maybe with undefined as Nothing:

errors = mappedErrors.valueOr(undefined)

Trouble is, the <U extends T> does not allow me to default to undefined. What is that constraint for?

[cbowdon]

Sorry, I honestly can't remember. It's been a couple of years since I spent real time on this library. Not a great answer I know!