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, 7 insertions, 2 deletions

diff --git a/library/lib.ml b/library/lib.ml
index e4617cafb..f8bb6bac5 100644
--- a/library/lib.ml
+++ b/library/lib.ml
@@ -428,8 +428,10 @@ let add_section_context ctx =
        sectab := (Context ctx :: vars,repl,abs)::sl
 
 let extract_hyps (secs,ohyps) =
+  let open Context.Named.Declaration in
   let rec aux = function
-    | (Variable (id,impl,poly,ctx)::idl,(id',b,t)::hyps) when Names.Id.equal id id' ->
+    | (Variable (id,impl,poly,ctx)::idl, decl::hyps) when Names.Id.equal id (get_id decl) ->
+      let (id',b,t) = to_tuple decl in
       let l, r = aux (idl,hyps) in 
 	(id',impl,b,t) :: l, if poly then Univ.ContextSet.union r ctx else r
     | (Variable (_,_,poly,ctx)::idl,hyps) ->
@@ -448,7 +450,10 @@ let instance_from_variable_context sign =
     | [] -> [] in
   Array.of_list (inst_rec sign)
 
-let named_of_variable_context ctx = List.map (fun (id,_,b,t) -> (id,b,t)) ctx
+let named_of_variable_context ctx = let open Context.Named.Declaration in
+                                    List.map (function id,_,None,t -> LocalAssum (id,t)
+                                                     | id,_,Some b,t -> LocalDef (id,b,t))
+                                             ctx
   
 let add_section_replacement f g poly hyps =
   match !sectab with