[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, bkpfail26.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, bkpfail26.out/p/p-D5Mg3foBSCrDbQDKH4WGSG/H.o )

bkpfail26.bkp:16:9: error:
    • Type constructor ‘T’ has conflicting definitions in the module
      and its hsig file
      Main module: type T :: * -> *
                   type T a = [a]
      Hsig file:  type role T nominal
                  type T :: * -> *
                  data T a
      Illegal parameterized type synonym in implementation of abstract data.
      (Try eta reducing your type synonym so that it is nullary.)
    • while checking that q:H implements signature H in p[H=q:H]