tidyBind env (Rec prs)
  = let
       (env', bndrs') = mapAccumL (tidyLetBndr env') env prs
    in
    map (tidyExpr env') (map snd prs)   =: \ rhss' ->
    (env', Rec (zip bndrs' rhss'))
tidyBind env (Rec prs)
  = let
       (env', bndrs') = mapAccumL (tidyLetBndr env') env prs
    in
    map (tidyExpr env') (map snd prs)   =: \ rhss' ->
    (env', Rec (zip bndrs' rhss'))
tidyBind env (Rec prs)
  = let
       (env', bndrs') = mapAccumL (tidyLetBndr env') env prs
    in
    map (tidyExpr env') (map snd prs)   =: \ rhss' ->
    (env', Rec (zip bndrs' rhss'))