Consider taking advantage of @mustuse?

[AndrejMitrovic]

The @mustuse attribute was implemented in DIP 1038.

I think it would be really nice to combine this with Expected in order to force client code to always handle return values of functions which can fail, in other words when their return type is Expected.

But this could also be a breaking change for the library.

Perhaps we could make this attribute optional or maybe introduce another type with this attribute which internally contains Expected? I can't think of a good way to make this look neat.

Curious about your thoughts.

And I wanted to say this is a great library and it's come really handy for me. Thanks for all your hard work!