Preserve realization headers in Coq printer.

src/printer/coq.ml

@@ -518,8 +518,9 @@ let read_deprecated_script ch in_context =
 
 let read_old_script =
   let axm = Str.regexp "\\(Axiom\\|Parameter\\)[ ]+\\([^ :(.]+\\)" in
+  let prelude = Str.regexp "(\\* This file is generated by Why3.*\\*)" in
   fun ch ->
-  let skip_to_empty = ref true in
+  let skip_to_empty = ref false in
   let last_empty_line = ref 0 in
   let sc = ref [] in
   try
@@ -538,6 +539,9 @@ let read_old_script =
         skip_to_empty := true) else
       if s = "(* Why3 goal *)" then
         (sc := read_old_proof ch :: !sc; skip_to_empty := true) else
+      if Str.string_match prelude s 0 then
+        (sc := Info "Why3 prelude" :: !sc;
+         skip_to_empty := true) else
       if s = "(* YOU MAY EDIT THE CONTEXT BELOW *)" then
         (sc := read_deprecated_script ch true; raise End_of_file) else
       if s = "(* YOU MAY EDIT THE PROOF BELOW *)" then
@@ -954,8 +958,6 @@ let print_decls ~old info fmt dl =
 let print_task printer_args ~realize ~ssreflect ?old fmt task =
   (* eprintf "Task:%a@.@." Pretty.print_task task; *)
   forget_all ();
-  print_prelude fmt printer_args.prelude;
-  print_th_prelude task fmt printer_args.th_prelude;
   (* find theories that are both used and realized from metas *)
   let realized_theories =
     Task.on_meta meta_realized_theory (fun mid args ->
@@ -982,8 +984,7 @@ let print_task printer_args ~realize ~ssreflect ?old fmt task =
         upd_realized_theories task
     | _ -> assert false in
   let realized_theories = upd_realized_theories task in
-  let realized_theories' =
-    Mid.map (fun (th,s) -> fprintf fmt "Require %s.@\n" s; th) realized_theories in
+  let realized_theories' = Mid.map fst realized_theories in
   let realized_symbols = Task.used_symbols realized_theories' in
   let local_decls = Task.local_decls task realized_symbols in
   (* eprintf "local_decls:%i@." (List.length local_decls); *)
@@ -1009,6 +1010,10 @@ let print_task printer_args ~realize ~ssreflect ?old fmt task =
   let old = ref (match old with
     | None -> []
     | Some ch -> read_old_script ch) in
+  ignore (output_till_statement fmt old "Why3 prelude");
+  print_prelude fmt printer_args.prelude;
+  print_th_prelude task fmt printer_args.th_prelude;
+  Mid.iter (fun _ (_, s) -> fprintf fmt "Require %s.@\n" s) realized_theories;
   print_decls ~old info fmt local_decls;
   output_remaining fmt !old