AmbiguousSet1b.agda:11,7-11
Ambiguous name Set₁. It could refer to any one of
  Set bound at
    agda-default-include-path/Agda/Primitive.agda:13,18-21
  Set₁ bound at AmbiguousSet1b.agda:6,3-7
(hint: Use C-c C-w (in Emacs) if you want to know why)
when scope checking Set₁
