[1 of 3] Processing p
  [1 of 2] Compiling H[sig]           ( p\H.hsig, nothing )
  [2 of 2] Compiling M                ( p\M.hs, nothing )
[2 of 3] Processing q
  Instantiating q
  [1 of 1] Compiling H                ( q\H.hs, bkpfail27.out\q\H.o )
[3 of 3] Processing r
  Instantiating r
  [1 of 1] Including p[H=q:H]
    Instantiating p[H=q:H]
    [1 of 2] Compiling H[sig]           ( p\H.hsig, bkpfail27.out\p\p-D5Mg3foBSCrDbQDKH4WGSG\H.o )

bkpfail27.bkp:15:9: error: [GHC-15843]
    • Type constructor ‘T’ has conflicting definitions in the module
      and its hsig file.
      Main module: type T :: *
                   type T = F
        Hsig file: type T :: *
                   data T
      Illegal implementation of abstract data: Invalid type family ‘F’.
    • While checking that ‘q:H’ implements signature ‘H’ in ‘p[H=q:H]’.