No, HM is unification based and requires no annotations at all.

Apparently it only gets away without annotations if the language doesn’t support subtyping? Here’s an explanation about why bidirectional type checking is better for that:

https://www.haskellforall.com/2022/06/the-appeal-of-bidirect...

It seems to me that type-checking that relies on global constraint-solving is usually a bad idea. Annotated function types result in less confusion about what a function does.