module Repro where

import Prim.RowList as RL

class What
      (a :: RL.RowList Type)
      (b :: Row Type)
      (c :: RL.RowList Type)
       | b -> a, c -> b -- , a -> c

instance What RL.Nil () RL.Nil

at src/Repro.purs:11:1 - 11:31 (line 11, column 1 - line 11, column 31)

  Type class instance head is invalid due to use of type

    ()

  All types appearing in instance declarations must be of the form T a_1 .. a_n, where each type a_i is of the same form, unless the type is fully determined by other type class arguments via functional dependencies.

in type class instance

  Repro.What Nil
             ()
             Nil