This blogpost explains and argues the claim that Ad-hoc polymorphism (Type-classes in Haskell/Scala/Purescript, Traits in Rust, Interfaces in Go/Java) makes code less type-safe.In other words: ad-hoc polymorphism makes it so that sometimes, after a refactor, code that is wrong and would not type-check without it, now still type-checks.
I think the author does not deserve Haskell