Yes, I understand. But by "implicitly" I really meant that. You don't see the type, only the compiler does. The programmer only sees the non-error part of the type (the "Right" part of Either).

> Either is a sum type. What if I don't want that.

Product types work as well, if you want. But unless your return type is a monoid (or like, a semilattice maybe?) then you're going to end up with Sum Types somewhere.

The vast, vast majority of software engineers and students work with sum types every day and they're totally fine with them. Most languages implicitly sum many values with null.