Using Barbies' AllBF in an instance head without UndecidableInstances

Question

I'd like to use AllBF from barbies in an instance head, like so:

import Barbies
import Barbies.Constraints

class MyClass a where

instance (ConstraintsB b, AllBF MyClass f b) => MyClass (Barbie b f) where

This fails because of a hidden kind-polymorphism. Simon says:

• Variable k occurs more often in the constraint AllBF MyClass f b than in the instance head MyClass (Barbie b f) (Use UndecidableInstances to permit this)

I'd like to avoid UndecidableInstances here. One thing I've tried is making my instance monomorphic in the kind of f:

instance (ConstraintsB b, AllBF MyClass (f :: Type -> Type) b) => MyClass (Barbie b f) where

However, this then results in a different error:

• Illegal nested constraint AllBF MyClass f b (Use UndecidableInstances to permit this)

Naively, I tried inlining the definition of AllBF, but that doesn't change anything:

instance (ConstraintsB b, AllB (ClassF MyClass (f :: Type -> Type)) b) => MyClass (Barbie b f) where

• Illegal nested constraint AllB (ClassF MyClass f) b (Use UndecidableInstances to permit this)

Is there a way to create this instance without turning on UndecidableInstances?