Allow declaring universe constraints at definition level.

Introduce a "+" modifier for universe and constraint declarations to
indicate that these can be extended in the final definition/proof.  By
default [Definition f] is equivalent to [Definition f@{+|+}], i.e
universes can be introduced and constraints as well. For [f@{}] or
[f@{i j}], the constraints can be extended, no universe introduced, to
maintain compatibility with existing developments. Use [f@{i j | }] to
indicate that no constraint (nor universe) can be introduced. These
kind of definitions could benefit from asynchronous processing.

Declarations of universe binders and constraints also works for
monomorphic definitions.

3 files changed, 84 insertions, 0 deletions

diff --git a/pretyping/pretyping.mllib b/pretyping/pretyping.mllib
index c8b3307d7..d04dcb8e3 100644
--- a/pretyping/pretyping.mllib
+++ b/pretyping/pretyping.mllib
@@ -29,3 +29,4 @@ Indrec
 Cases
 Pretyping
 Unification
+Univdecls
diff --git a/pretyping/univdecls.ml b/pretyping/univdecls.ml
new file mode 100644
index 000000000..d7c42d03a
--- /dev/null
+++ b/pretyping/univdecls.ml
@@ -0,0 +1,64 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+open Names
+open Nameops
+open CErrors
+open Pp
+
+(** Local universes and constraints declarations *)
+type universe_decl =
+  (Id.t Loc.located list, Univ.Constraint.t) Misctypes.gen_universe_decl
+
+let default_univ_decl =
+  let open Misctypes in
+  { univdecl_instance = [];
+    univdecl_extensible_instance = true;
+    univdecl_constraints = Univ.Constraint.empty;
+    univdecl_extensible_constraints = true }
+
+let interp_univ_constraints env evd cstrs =
+  let open Misctypes in
+  let u_of_id x =
+    match x with
+    | Misctypes.GProp -> Loc.tag Univ.Level.prop
+    | GSet  -> Loc.tag Univ.Level.set
+    | GType None | GType (Some (_, Anonymous)) ->
+       user_err ~hdr:"interp_constraint"
+                     (str "Cannot declare constraints on anonymous universes")
+    | GType (Some (loc, Name id)) ->
+       try loc, Evd.universe_of_name evd (Id.to_string id)
+       with Not_found ->
+         user_err ?loc ~hdr:"interp_constraint" (str "Undeclared universe " ++ pr_id id)
+  in
+  let interp (evd,cstrs) (u, d, u') =
+    let lloc, ul = u_of_id u and rloc, u'l = u_of_id u' in
+    let cstr = (ul,d,u'l) in
+    let cstrs' = Univ.Constraint.add cstr cstrs in
+    try let evd = Evd.add_constraints evd (Univ.Constraint.singleton cstr) in
+        evd, cstrs'
+    with Univ.UniverseInconsistency e ->
+      user_err  ~hdr:"interp_constraint" (str "Universe inconsistency" (* TODO *))
+  in
+  List.fold_left interp (evd,Univ.Constraint.empty) cstrs
+
+let interp_univ_decl env decl = 
+  let open Misctypes in
+  let pl = decl.univdecl_instance in
+  let evd = Evd.from_ctx (Evd.make_evar_universe_context env (Some pl)) in
+  let evd, cstrs = interp_univ_constraints env evd decl.univdecl_constraints in
+  let decl = { univdecl_instance = pl;
+    univdecl_extensible_instance = decl.univdecl_extensible_instance;
+    univdecl_constraints = cstrs;
+    univdecl_extensible_constraints = decl.univdecl_extensible_constraints }
+  in evd, decl
+
+let interp_univ_decl_opt env l =
+  match l with
+  | None -> Evd.from_env env, default_univ_decl
+  | Some decl -> interp_univ_decl env decl
diff --git a/pretyping/univdecls.mli b/pretyping/univdecls.mli
new file mode 100644
index 000000000..0c3b749cb
--- /dev/null
+++ b/pretyping/univdecls.mli
@@ -0,0 +1,19 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+(** Local universe and constraint declarations. *)
+type universe_decl =
+  (Names.Id.t Loc.located list, Univ.Constraint.t) Misctypes.gen_universe_decl
+
+val default_univ_decl : universe_decl
+
+val interp_univ_decl : Environ.env -> Vernacexpr.universe_decl_expr ->
+                       Evd.evar_map * universe_decl
+
+val interp_univ_decl_opt : Environ.env -> Vernacexpr.universe_decl_expr option ->
+                       Evd.evar_map * universe_decl