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, 22 insertions, 17 deletions

diff --git a/kernel/typeops.ml b/kernel/typeops.ml
index f31cba0a8..eeb12a2b4 100644
--- a/kernel/typeops.ml
+++ b/kernel/typeops.ml
@@ -77,8 +77,9 @@ let judge_of_type u =
 (*s Type of a de Bruijn index. *)
 
 let judge_of_relative env n =
+  let open Context.Rel.Declaration in
   try
-    let (_,_,typ) = lookup_rel n env in
+    let typ = get_type (lookup_rel n env) in
     { uj_val  = mkRel n;
       uj_type = lift n typ }
   with Not_found ->
@@ -98,18 +99,20 @@ let judge_of_variable env id =
    variables of the current env.
    Order does not have to be checked assuming that all names are distinct *)
 let check_hyps_inclusion env c sign =
+  let open Context.Named.Declaration in
   Context.Named.fold_outside
-    (fun (id,b1,ty1) () ->
+    (fun d1 () ->
+      let id = get_id d1 in
       try
-        let (_,b2,ty2) = lookup_named id env in
-        conv env ty2 ty1;
-        (match b2,b1 with
-        | None, None -> ()
-        | None, Some _ ->
+        let d2 = lookup_named id env in
+        conv env (get_type d2) (get_type d1);
+        (match d2,d1 with
+        | LocalAssum _, LocalAssum _ -> ()
+        | LocalAssum _, LocalDef _ ->
             (* This is wrong, because we don't know if the body is
                needed or not for typechecking: *) ()
-        | Some _, None -> raise NotConvertible
-        | Some b2, Some b1 -> conv env b2 b1);
+        | LocalDef _, LocalAssum _ -> raise NotConvertible
+        | LocalDef (_,b2,_), LocalDef (_,b1,_) -> conv env b2 b1);
       with Not_found | NotConvertible | Option.Heterogeneous ->
         error_reference_variables env id c)
     sign
@@ -124,9 +127,10 @@ let extract_level env p =
   match kind_of_term c with Sort (Type u) -> Univ.Universe.level u | _ -> None
 
 let extract_context_levels env l =
-  let fold l (_, b, p) = match b with
-  | None -> extract_level env p :: l
-  | _ -> l
+  let open Context.Rel.Declaration in
+  let fold l = function
+    | LocalAssum (_,p) -> extract_level env p :: l
+    | LocalDef _ -> l
   in
   List.fold_left fold [] l
 
@@ -416,6 +420,7 @@ let type_fixpoint env lna lar vdefj =
     Ind et Constructsi un jour cela devient des constructions
     arbitraires et non plus des variables *)
 let rec execute env cstr =
+  let open Context.Rel.Declaration in
   match kind_of_term cstr with
     (* Atomic terms *)
     | Sort (Prop c) ->
@@ -458,13 +463,13 @@ let rec execute env cstr =
 
     | Lambda (name,c1,c2) ->
       let varj = execute_type env c1 in
-      let env1 = push_rel (name,None,varj.utj_val) env in
+      let env1 = push_rel (LocalAssum (name,varj.utj_val)) env in
       let j' = execute env1 c2 in
         judge_of_abstraction env name varj j'
 
     | Prod (name,c1,c2) ->
       let varj = execute_type env c1 in
-      let env1 = push_rel (name,None,varj.utj_val) env in
+      let env1 = push_rel (LocalAssum (name,varj.utj_val)) env in
       let varj' = execute_type env1 c2 in
 	judge_of_product env name varj varj'
 
@@ -472,7 +477,7 @@ let rec execute env cstr =
       let j1 = execute env c1 in
       let j2 = execute_type env c2 in
       let _ = judge_of_cast env j1 DEFAULTcast j2 in
-      let env1 = push_rel (name,Some j1.uj_val,j2.utj_val) env in
+      let env1 = push_rel (LocalDef (name,j1.uj_val,j2.utj_val)) env in
       let j' = execute env1 c3 in
         judge_of_letin env name j1 j2 j'
 
@@ -550,10 +555,10 @@ let infer_v env cv =
 let infer_local_decl env id = function
   | LocalDef c ->
       let j = infer env c in
-      (Name id, Some j.uj_val, j.uj_type)
+      Context.Rel.Declaration.LocalDef (Name id, j.uj_val, j.uj_type)
   | LocalAssum c ->
       let j = infer env c in
-      (Name id, None, assumption_of_judgment env j)
+      Context.Rel.Declaration.LocalAssum (Name id, assumption_of_judgment env j)
 
 let infer_local_decls env decls =
   let rec inferec env = function