CLEANUP: Context.{Rel,Named}.Declaration.t

  Originally, rel-context was represented as:

    Context.rel_context = Names.Name.t * Constr.t option * Constr.t

  Now it is represented as:

    Context.Rel.t = LocalAssum of Names.Name.t * Constr.t
                  | LocalDef of Names.Name.t * Constr.t * Constr.t

  Originally, named-context was represented as:

    Context.named_context = Names.Id.t * Constr.t option * Constr.t

  Now it is represented as:

    Context.Named.t = LocalAssum of Names.Id.t * Constr.t
                    | LocalDef of Names.Id.t * Constr.t * Constr.t

Motivation:

  (1) In "tactics/hipattern.ml4" file we define "test_strict_disjunction"
      function which looked like this:

        let test_strict_disjunction n lc =
          Array.for_all_i (fun i c ->
            match (prod_assum (snd (decompose_prod_n_assum n c))) with
            | [_,None,c] -> isRel c && Int.equal (destRel c) (n - i)
            | _ -> false) 0 lc

      Suppose that you do not know about rel-context and named-context.
      (that is the case of people who just started to read the source code)
      Merlin would tell you that the type of the value you are destructing
      by "match" is:

        'a * 'b option * Constr.t                    (* worst-case scenario *)

      or

        Named.Name.t * Constr.t option * Constr.t    (* best-case scenario (?) *)

      To me, this is akin to wearing an opaque veil.
      It is hard to figure out the meaning of the values you are looking at.
      In particular, it is hard to discover the connection between the value
      we are destructing above and the datatypes and functions defined
      in the "kernel/context.ml" file.

      In this case, the connection is there, but it is not visible
      (between the function above and the "Context" module).

      ------------------------------------------------------------------------

      Now consider, what happens when the reader see the same function
      presented in the following form:

        let test_strict_disjunction n lc =
          Array.for_all_i (fun i c ->
            match (prod_assum (snd (decompose_prod_n_assum n c))) with
            | [LocalAssum (_,c)] -> isRel c && Int.equal (destRel c) (n - i)
            | _ -> false) 0 lc

      If the reader haven't seen "LocalAssum" before, (s)he can use Merlin
      to jump to the corresponding definition and learn more.

      In this case, the connection is there, and it is directly visible
      (between the function above and the "Context" module).

  (2) Also, if we already have the concepts such as:
      - local declaration
      - local assumption
      - local definition
      and we describe these notions meticulously in the Reference Manual,
      then it is a real pity not to reinforce the connection
      of the actual code with the abstract description we published.

1 files changed, 11 insertions, 7 deletions

diff --git a/printing/printer.ml b/printing/printer.ml
index 93850e41fa..5f4371f2d0 100644
--- a/printing/printer.ml
+++ b/printing/printer.ml
@@ -262,16 +262,19 @@ let pr_var_decl_skel pr_id env sigma (id,c,typ) =
   let ptyp = (str" : " ++ pt) in
   (pr_id id ++ hov 0 (pbody ++ ptyp))
 
-let pr_var_decl env sigma (id,c,typ) =
-  pr_var_decl_skel pr_id env sigma (id,c,typ)
+let pr_var_decl env sigma d =
+  pr_var_decl_skel pr_id env sigma (Context.Named.Declaration.to_tuple d)
 
 let pr_var_list_decl env sigma (l,c,typ) =
   hov 0 (pr_var_decl_skel (fun ids -> prlist_with_sep pr_comma pr_id ids) env sigma (l,c,typ))
 
-let pr_rel_decl env sigma (na,c,typ) =
-  let pbody = match c with
-    | None -> mt ()
-    | Some c ->
+let pr_rel_decl env sigma decl =
+  let open Context.Rel.Declaration in
+  let na = get_name decl in
+  let typ = get_type decl in
+  let pbody = match decl with
+    | LocalAssum _ -> mt ()
+    | LocalDef (_,c,_) ->
 	(* Force evaluation *)
 	let pb = pr_lconstr_env env sigma c in
 	let pb = if isCast c then surround pb else pb in
@@ -420,7 +423,8 @@ let pr_evgl_sign sigma evi =
   | None -> [], []
   | Some f -> List.filter2 (fun b c -> not b) f (evar_context evi)
   in
-  let ids = List.rev_map pi1 l in
+  let open Context.Named.Declaration in
+  let ids = List.rev_map get_id l in
   let warn =
     if List.is_empty ids then mt () else
       (str "(" ++ prlist_with_sep pr_comma pr_id ids ++ str " cannot be used)")