expr_fvs (Coercion co) fv_cand in_scope acc =
  tyCoFVsOfCo co fv_cand in_scope acc
expr_fvs (Coercion co) fv_cand in_scope acc =
  tyCoFVsOfCo co fv_cand in_scope acc
expr_fvs (Coercion co) fv_cand in_scope acc =
  tyCoFVsOfCo co fv_cand in_scope acc