anchor.diff:    | EBufCreateNoInit of lifetime * expr
     | EAbortT of string * typ
     | EComment of string * expr * string
  -
  +  | EStandaloneComment of string
   
   and op =
     | Add | AddW | Sub | SubW | Div | DivW | Mult | MultW | Mod
  
positive.code:           failwith "Cannot extract comment applied to a non-literal"
        end
  
    | MLE_App ({ expr = MLE_Name ([ "C" ], "comment_gen") }, args) ->
       failwith ("comment_gen called with wrong number of arguments: " ^ string_of_int (List.length args))
  
    | MLE_App ({ expr = MLE_Name ([ "LowStar"; "Literal" ], "buffer_of_literal") }, [ { expr = e } ]) ->
        begin match e with
  
negative.code: - v27: Added PConstant
  - v28: added many things for which the AST wasn't bumped; bumped it for
    TConstBuf which will expect will be used soon
  *)
  
  (* COPY-PASTED ****************************************************************)
  