{-# LANGUAGE UndecidableInstances, AllowAmbiguousTypes, KindSignatures, TypeApplications, FlexibleInstances, ConstraintKinds #-}
     
    import Data.Kind (Constraint, Type)
     
    main = print "ok"
     
    class A (m :: Type -> Type)
     
    class B (m :: Type -> Type)
     
    instance A m => B m
     
    data C (a :: Type)
     
    instance A C
     
    data D (a :: Type)
     
    instance {-# OVERLAPPING #-} B D
     
    data E (a :: Type)
    
    implicitly :: a => ()
    implicitly = ()
     
    test = implicitly @(A C)
    test1 = implicitly @(B C)
    --test2 = implicitly @(A D) -- doesn't compile
    test3 = implicitly @(B D)
    --test4 = implicitly @(A E) -- doesn't compile
    --test5 = implicitly @(B E) -- doesn't compile