{-# 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

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