expr_fvs (Tick t expr) fv_cand in_scope acc =
  (tickish_fvs t `unionFV` expr_fvs expr) fv_cand in_scope acc
expr_fvs (Tick t expr) fv_cand in_scope acc =
  (tickish_fvs t `unionFV` expr_fvs expr) fv_cand in_scope acc
expr_fvs (Tick t expr) fv_cand in_scope acc =
  (tickish_fvs t `unionFV` expr_fvs expr) fv_cand in_scope acc