Less footguns in universe handling: remove subst_instance_context.

This function was lurking around, waiting to bite anybody willing to use it.
We use instead a better API, correct and much less error-prone.

4 files changed, 41 insertions, 38 deletions

diff --git a/checker/environ.ml b/checker/environ.ml
index 11b8ea67cc..d3f393c651 100644
--- a/checker/environ.ml
+++ b/checker/environ.ml
@@ -122,8 +122,7 @@ type const_evaluation_result = NoBody | Opaque | IsProj
 let constraints_of cb u =
   match cb.const_universes with
   | Monomorphic_const _ -> Univ.Constraint.empty
-  | Polymorphic_const ctx -> 
-    Univ.UContext.constraints (Univ.subst_instance_context u ctx)
+  | Polymorphic_const ctx -> Univ.AUContext.instantiate u ctx
 
 let map_regular_arity f = function
   | RegularArity a as ar -> 
diff --git a/checker/reduction.ml b/checker/reduction.ml
index 0b605820d7..6d8783d7e5 100644
--- a/checker/reduction.ml
+++ b/checker/reduction.ml
@@ -166,16 +166,14 @@ let convert_inductive_instances cv_pb cumi u u' univs =
   else
     let comp_cst =
       let comp_subst = (Univ.Instance.append u u') in
-      Univ.UContext.constraints
-      (Univ.subst_instance_context comp_subst ind_subtypctx)
+      Univ.AUContext.instantiate comp_subst ind_subtypctx
     in
     let comp_cst =
       match cv_pb with
         CONV ->
         let comp_cst' =
           let comp_subst = (Univ.Instance.append u' u) in
-          Univ.UContext.constraints
-            (Univ.subst_instance_context comp_subst ind_subtypctx)
+          Univ.AUContext.instantiate comp_subst ind_subtypctx
         in
         Univ.Constraint.union comp_cst comp_cst'
       | CUMUL -> comp_cst
diff --git a/checker/univ.ml b/checker/univ.ml
index 4eebcb25b9..600af230c9 100644
--- a/checker/univ.ml
+++ b/checker/univ.ml
@@ -1160,6 +1160,33 @@ struct
   
 end
 
+(** Substitute instance inst for ctx in csts *)
+
+let subst_instance_level s l =
+  match l.Level.data with
+  | Level.Var n -> s.(n) 
+  | _ -> l
+
+let subst_instance_instance s i = 
+  Array.smartmap (fun l -> subst_instance_level s l) i
+
+let subst_instance_universe s u =
+  let f x = Universe.Expr.map (fun u -> subst_instance_level s u) x in
+  let u' = Universe.smartmap f u in
+    if u == u' then u
+    else Universe.sort u'
+
+let subst_instance_constraint s (u,d,v as c) =
+  let u' = subst_instance_level s u in
+  let v' = subst_instance_level s v in
+    if u' == u && v' == v then c
+    else (u',d,v')
+
+let subst_instance_constraints s csts =
+  Constraint.fold 
+    (fun c csts -> Constraint.add (subst_instance_constraint s c) csts)
+    csts Constraint.empty
+
 type universe_instance = Instance.t
 
 type 'a puniverses = 'a * Instance.t
@@ -1185,7 +1212,15 @@ end
 
 type universe_context = UContext.t
 
-module AUContext = UContext
+module AUContext =
+struct
+  include UContext
+
+  let instantiate inst (u, cst) =
+    assert (Array.length u = Array.length inst);
+    subst_instance_constraints inst cst
+
+end
 
 type abstract_universe_context = AUContext.t
 
@@ -1264,36 +1299,6 @@ let subst_univs_level_universe subst u =
     if u == u' then u
     else Universe.sort u'
 
-(** Substitute instance inst for ctx in csts *)
-
-let subst_instance_level s l =
-  match l.Level.data with
-  | Level.Var n -> s.(n) 
-  | _ -> l
-
-let subst_instance_instance s i = 
-  Array.smartmap (fun l -> subst_instance_level s l) i
-
-let subst_instance_universe s u =
-  let f x = Universe.Expr.map (fun u -> subst_instance_level s u) x in
-  let u' = Universe.smartmap f u in
-    if u == u' then u
-    else Universe.sort u'
-
-let subst_instance_constraint s (u,d,v as c) =
-  let u' = subst_instance_level s u in
-  let v' = subst_instance_level s v in
-    if u' == u && v' == v then c
-    else (u',d,v')
-
-let subst_instance_constraints s csts =
-  Constraint.fold 
-    (fun c csts -> Constraint.add (subst_instance_constraint s c) csts)
-    csts Constraint.empty
-
-let subst_instance_context inst (inner_inst, inner_constr) =
-  (inner_inst, subst_instance_constraints inst inner_constr)
-
 let make_abstract_instance (ctx, _) = 
   Array.mapi (fun i l -> Level.var i) ctx
 
diff --git a/checker/univ.mli b/checker/univ.mli
index faa682cbf0..75c76cd129 100644
--- a/checker/univ.mli
+++ b/checker/univ.mli
@@ -211,6 +211,8 @@ sig
   val instance : t -> Instance.t
   val size : t -> int
 
+  val instantiate : Instance.t -> t -> Constraint.t
+
 end
 
 type abstract_universe_context = AUContext.t
@@ -277,7 +279,6 @@ val subst_univs_universe : universe_subst_fn -> universe -> universe
 (** Substitution of instances *)
 val subst_instance_instance : universe_instance -> universe_instance -> universe_instance
 val subst_instance_universe : universe_instance -> universe -> universe
-val subst_instance_context : universe_instance -> abstract_universe_context -> universe_context
 
 (* val make_instance_subst : universe_instance -> universe_level_subst *)
 (* val make_inverse_instance_subst : universe_instance -> universe_level_subst *)