anchor.diff:          rebuild_closure cfg env stack t
   
         | Tm_meta(t', m) ->
  -        let stack = Meta(m, t.pos)::stack in
  +        let stack = Meta(env, m, t.pos)::stack in
           inline_closure_env cfg env stack t'
   
         | Tm_let((false, [lb]), body) -> //non-recursive let
  
positive.code:                    | Inl m -> Meta_monadic (m, t)
                     | Inr (m, m') -> Meta_monadic_lift (m, m', t)
      in
      norm cfg env (Meta(metadata, head.pos)::stack) head
  
  and do_reify_monadic fallback cfg env stack (head : term) (m : monad_name) (t : typ) : term =
      (* Precondition: the stack head is an App (reify, ...) *)
  
negative.code:               let stack' =
                  let tail = (Cfg cfg)::stack in
                  if cfg.debug.print_normalized
                  then (Debug(t, BU.now())::tail)
                  else tail in
                norm cfg' env stack' tm
              end
  