From b0e52bbbc52691343b3fab927b20c1f512f59976 Mon Sep 17 00:00:00 2001
From: Pierre Letouzey
Date: Fri, 21 Jul 2017 12:02:36 +0200
Subject: Extraction: reduce primitive projections in types (fix bug 4709)

---
 API/API.mli                      | 2 ++
 plugins/extraction/extraction.ml | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/API/API.mli b/API/API.mli
index bb24d5768f..d136deb70c 100644
--- a/API/API.mli
+++ b/API/API.mli
@@ -169,6 +169,8 @@ sig
     val map : (Constant.t -> Constant.t) -> t -> t
     val constant : t -> Constant.t
     val equal : t -> t -> bool
+    val unfolded : t -> bool
+    val unfold : t -> t
   end
 
   type evaluable_global_reference =
diff --git a/plugins/extraction/extraction.ml b/plugins/extraction/extraction.ml
index 3661faadab..996df1a47d 100644
--- a/plugins/extraction/extraction.ml
+++ b/plugins/extraction/extraction.ml
@@ -295,7 +295,11 @@ let rec extract_type env db j c args =
     | Ind ((kn,i),u) ->
 	let s = (extract_ind env kn).ind_packets.(i).ip_sign in
 	extract_type_app env db (IndRef (kn,i),s) args
-    | Case _ | Fix _ | CoFix _ | Proj _ -> Tunknown
+    | Proj (p,t) ->
+       (* Let's try to reduce, if it hasn't already been done. *)
+       if Projection.unfolded p then Tunknown
+       else extract_type env db j (Term.mkProj (Projection.unfold p, t)) args
+    | Case _ | Fix _ | CoFix _ -> Tunknown
     | _ -> assert false
 
 (*s Auxiliary function dealing with type application.
-- 
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