[1 of 3] Processing sig
  [1 of 2] Compiling A[sig]           ( sig/A.hsig, nothing )
  [2 of 2] Compiling M                ( sig/M.hs, nothing )
[2 of 3] Processing mod
  Instantiating mod
  [1 of 1] Compiling A                ( mod/A.hs, bkpfail11.out/mod/A.o )
[3 of 3] Processing join
  Instantiating join
  [1 of 1] Including sig[A=mod:A]
    Instantiating sig[A=mod:A]
    [1 of 2] Compiling A[sig]           ( sig/A.hsig, bkpfail11.out/sig/sig-HyoWTHt34SDIRGEX0vZ8iN/A.o )

bkpfail11.out/sig/sig-HyoWTHt34SDIRGEX0vZ8iN/../A.hi:1:1: error:
    • No instance for (GHC.Show.Show X)
        arising when attempting to show that
        instance [safe] GHC.Show.Show T -- Defined at bkpfail11.bkp:5:18
        is provided by ‘mod:A’
    • while checking that mod:A implements signature A in sig[A=mod:A]