From c3a4c70688db675c79878df33b4210a4315baf54 Mon Sep 17 00:00:00 2001
From: sacerdot
Date: Wed, 29 Sep 2004 13:51:50 +0000
Subject: The Prod special case works only when the premise is of type Prop.
 This is now checked.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@6156 85f007b7-540e-0410-9357-904b9bb8a0f7
---
 tactics/setoid_replace.ml | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/tactics/setoid_replace.ml b/tactics/setoid_replace.ml
index 4045816eba..9c10ce51c0 100644
--- a/tactics/setoid_replace.ml
+++ b/tactics/setoid_replace.ml
@@ -1058,8 +1058,19 @@ let mark_occur gl t in_c input_relation input_direction =
             (str "Cannot rewrite in the type of a variable bound " ++
              str "in a dependent product.")
           else 
-           aux output_relation output_direction
-            (mkApp ((Lazy.force coq_impl), [| c1 ; c2 |]))
+           let typeofc1 = Tacmach.pf_type_of gl c1 in
+            if not (Tacmach.pf_conv_x gl typeofc1 mkProp) then
+             (* to avoid this error we should introduce an impl relation
+                whose first argument is Type instead of Prop *)
+             errorlabstrm "Setoid_replace"
+              (str "Rewriting in a product A -> B is possible only when A " ++
+               str "is a proposition (i.e. A is of type Prop). The type " ++
+               prterm c1 ++ str " has type " ++ prterm typeofc1 ++
+               str " that is not convertible to Prop. If you need this " ++
+               str "feature, please ask the author.")
+            else
+             aux output_relation output_direction
+              (mkApp ((Lazy.force coq_impl), [| c1 ; c2 |]))
       | _ -> [ToKeep (in_c,output_relation,output_direction)]
  in
   let aux2 output_relation output_direction =
-- 
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