[sertbdfgbnfgsd]

Interesting case! Lets discuss.

I don't know/use Unitful, but if that function didn't fail it's because the guys who wrote Unitful defined a promotion rule from Int to their Unit thingy. So.... that's how their type works. Don't use it. Or better, open an issue on github, they might have an explanation that's escaping us. I suspect it has to do with their mental model of what Unitful is supposed to achieve.

Let me tell you that my intuition agrees with you. As an ex-physicist, if I was designing a lib called Unitful I wouldn't let you sum sum 1 meter plus 1 unitless thing.

EDIT:

Actually, I just tried running your code and I do get DimensionError

    foo(2.0m)
    ERROR: DimensionError: 2.0 m and 1.0 are not dimensionally compatible.

I'm guessing you have some seriously outdated versions of something?

EDIT2: Sorry I misread you. You do get an error. Ok I see your point. Maybe the Julia docs should more explicit about what the Number interface entails. Is `+ 1` allowed? You're assuming the answer is obvious, but it's not to me. In particular, that's not generic at all. You're probably right about `+ oneunit(T)`