[1 of 3] Processing p
  [1 of 2] Compiling A[sig]           ( p\A.hsig, nothing )
  [2 of 2] Compiling M                ( p\M.hs, nothing )
[2 of 3] Processing q
  Instantiating q
  [1 of 1] Compiling A                ( q\A.hs, bkpfail46.out\q\A.o )
[3 of 3] Processing r
  Instantiating r
  [1 of 1] Including p[A=q:A]
    Instantiating p[A=q:A]
    [1 of 2] Compiling A[sig]           ( p\A.hsig, bkpfail46.out\p\p-HVmFlcYSefiK5n1aDP1v7x\A.o )

bkpfail46.bkp:16:9: error: [GHC-15843]
    • Type constructor ‘K’ has conflicting definitions in the module
      and its hsig file.
      Main module: type K :: * -> Constraint
                   type K a = GHC.Classes.Eq a :: Constraint
        Hsig file: type K :: * -> Constraint
                   class K a
      Illegal parameterized type synonym in implementation of abstract data.
    • While checking that ‘q:A’ implements signature ‘A’ in ‘p[A=q:A]’.
    Suggested fix:
      If possible, eta-reduce the type synonym ‘K’ so that it is nullary.