[1 of 3] Processing q
  [1 of 2] Compiling M1               ( q\M1.hs, nothing )
  [2 of 2] Compiling M2[sig]          ( q\M2.hsig, nothing )
[2 of 3] Processing m2
  Instantiating m2
  [1 of 1] Compiling M2               ( m2\M2.hs, nothing )
[3 of 3] Processing p
  Instantiating p
  [1 of 1] Including q[M2=m2:M2]
    Instantiating q[M2=m2:M2]
    [1 of 2] Compiling M1               ( q\M1.hs, nothing )
    [2 of 2] Compiling M2[sig]          ( q\M2.hsig, nothing )

bkpfail03.bkp:3:9: error: [GHC-12424]
    • The hsig file (re)exports ‘M1.M’
      but the implementing module exports a different identifier ‘M2.M’
    • While checking that ‘m2:M2’ implements signature ‘M2’ in ‘q[M2=m2:M2]’.