[Haskell-cafe] problem with compiler error message

Hello cafe! It seems that this behavior is wrong:

class Foo a where { type Bar a; baz :: a -> Bar a } baz zzz -- zzz is not in scope <interactive>:17:1: error: • Couldn't match expected type ‘Bar a’ with actual type ‘Bar a0’ NB: ‘Bar’ is a type function, and may not be injective The type variable ‘a0’ is ambiguous • In the ambiguity check for the inferred type for ‘it’ To defer the ambiguity check to use sites, enable AllowAmbiguousTypes When checking the inferred type it :: forall a. Bar a

As opposite - correct behavior:

:t negate negate :: Num a => a -> a negate zzz <interactive>:19:8: error: Variable not in scope: zzz

Best regards, Dmitry