Issue1194m.agda:23,11-12
Ambiguous name _∷_. It could refer to any one of
  A._∷_ bound at
    Issue1194m.agda:10,5-8
  B._∷_ bound at
    Issue1194m.agda:17,5-8
(hint: Use C-c C-w (in Emacs) if you want to know why)
when scope checking Set ∷ Set
