[1 of 2] Processing p
  [1 of 1] Compiling A[sig]           ( p\A.hsig, nothing )
[2 of 2] Processing q
  [1 of 3] Compiling A[sig]           ( q\A.hsig, nothing )
  [2 of 3] Compiling M                ( q\M.hs, nothing )

bkpfail49.bkp:11:13: error: [GHC-76037]
    Not in scope: data constructor ‘A.True’
    NB: the module ‘A’ does not export ‘True’.
  [3 of 3] Instantiating p