{-# LANGUAGE UndecidableInstances, KindSignatures, TypeApplications, FlexibleInstances #-}

class A (m :: * -> *)

class A1 (m :: * -> *)

class B (m :: * -> *)

instance A m => B m

instance {-# OVERLAPPING #-} A1 m => B m

data C a

instance A C

data D a

instance A1 D

implicitly :: a => ()
implicitly = ()

test = implicitly @(B C)
test1 = implicitly @(B D)

main = print "ok"