Change return value from `T2 | null | undefined` to `T2 | null` and `T2 | undefined`?

[sorenlouv]

I'm using idx with Typescript and running into some minor problems with the return type.
Example:

interface User {
  user?: { name?: string };
}
function getName(user: User) {
 return idx(user, _ => _.user.name);
}

I would expect the return type of getName to be string | undefined. However the type is string | undefined | null.
I would think that it can be inferred at compile time that null is not a possible return type in case case, given the interface User.

Is there any reason for this behaviour or is it a limitation with Typescript?

[sorenlouv]

Closing after conversation in #71