From 066ba7e26f3c6849b9210e5ffee8d2d0c17c041d Mon Sep 17 00:00:00 2001
From: msozeau
Date: Thu, 27 Nov 2008 17:54:05 +0000
Subject: Fix (?) a pattern matching compilation problem: << Axiom A : nat ->
 bool. Definition foo :=   match A 0 with     | true => true     | k => k  
 end. Print foo. >>

[A 0] is duplicated in the [k => k] branch!


git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@11640 85f007b7-540e-0410-9357-904b9bb8a0f7
---
 pretyping/cases.ml | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/pretyping/cases.ml b/pretyping/cases.ml
index 3839561bf0..a4d0b25ce9 100644
--- a/pretyping/cases.ml
+++ b/pretyping/cases.ml
@@ -150,8 +150,11 @@ let mkSpecialLetInJudge j (na,(deppat,nondeppat,d,t)) =
     then
       (* The body of pat is not needed to type j - see *)
       (* insert_aliases - and both deppat and nondeppat have the *)
-      (* same type, then one can freely substitute one by the other *)
-      subst1 nondeppat j.uj_val
+      (* same type, then one can freely substitute one by the other. *)
+      (* We use nondeppat only if it's a Rel to preserve sharing. *)
+      if isRel nondeppat then
+        subst1 nondeppat j.uj_val
+      else subst1 deppat j.uj_val
     else
       (* The body of pat is not needed to type j but its value *)
       (* is dependent in the type of j; our choice is to *)
-- 
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