Yes, you'd need an automated way to catch the API breakage, which would be particularly tricky.

And even with very strict typing, the breaking change showcased in the article wouldn't have been caught, the API stayed the same, it just behave differently. Not every backward incompatible change is as simple as a function signature change.

When I tried to submit a package to Hackage, I was asked if I was aware of the packaging guidelines. The person who I emailed to register also inspected my package and told me that my dependencies were wrong and not compliant.

I really don't think this is a scalable approach and was really surprised that someone took the time to check my dependencies personally. My experience may just be rare.

I meant more on the human side than automated. Haskell doesn't have that much to do with formal verification in usual use. I'm not sure what the best policy for a good yet vibrant package ecosystem is.