From 35fba70509d9fb219b2a88f8e7bd246b2671b39b Mon Sep 17 00:00:00 2001
From: Gaëtan Gilbert
Date: Thu, 9 Nov 2017 17:27:58 +0100
Subject: Simplification: cumulativity information is variance information.

Since cumulativity of an inductive type is the universe constraints
which make a term convertible with its universe-renamed copy, the only
constraints we can get are between a universe and its copy.

As such we do not need to be able to represent arbitrary constraints
between universes and copied universes in a double-sized ucontext,
instead we can just keep around an array describing whether a bound
universe is covariant, invariant or irrelevant (CIC has no
contravariant conversion rule).

Printing is fairly obtuse and should be improved: when we print the
CumulativityInfo we add marks to the universes of the instance: = for
invariant, + for covariant and * for irrelevant. ie

         Record Foo@{i j k} := { foo : Type@{i} -> Type@{j} }.
         Print Foo.

gives

        Cumulative Record Foo : Type@{max(i+1, j+1)} := Build_Foo
          { foo : Type@{i} -> Type@{j} }
          (* =i +j *k |=  *)
---
 pretyping/evarconv.ml | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

(limited to 'pretyping/evarconv.ml')

diff --git a/pretyping/evarconv.ml b/pretyping/evarconv.ml
index 41c4616f79..dc3acbc3e2 100644
--- a/pretyping/evarconv.ml
+++ b/pretyping/evarconv.ml
@@ -353,19 +353,7 @@ let exact_ise_stack2 env evd f sk1 sk2 =
 let check_leq_inductives evd cumi u u' =
   let u = EConstr.EInstance.kind evd u in
   let u' = EConstr.EInstance.kind evd u' in
-  let length_ind_instance =
-    Univ.AUContext.size (Univ.ACumulativityInfo.univ_context cumi)
-  in
-  let ind_sbcst =  Univ.ACumulativityInfo.subtyp_context cumi in
-  if not ((length_ind_instance = Univ.Instance.length u) &&
-          (length_ind_instance = Univ.Instance.length u')) then
-     anomaly (Pp.str "Invalid inductive subtyping encountered!")
-  else
-    begin
-     let comp_subst = (Univ.Instance.append u u') in
-     let comp_cst =  Univ.AUContext.instantiate comp_subst ind_sbcst in
-     Evd.add_constraints evd comp_cst
-    end
+  Evd.add_constraints evd (Reduction.get_cumulativity_constraints CUMUL cumi u u')
 
 let rec evar_conv_x ts env evd pbty term1 term2 =
   let term1 = whd_head_evar evd term1 in
-- 
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