From 8bb85530fbf5b6de1cb268004611c6f76fb5871e Mon Sep 17 00:00:00 2001
From: Gaëtan Gilbert
Date: Tue, 7 May 2019 15:09:26 +0200
Subject: Avoid trivial (u=u) constraints in AcyclicGraph.constraints_for

Not sure how often this happens in practice but it seems it could.
---
 lib/acyclicGraph.ml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'lib')

diff --git a/lib/acyclicGraph.ml b/lib/acyclicGraph.ml
index 7d04c8f5a1..e1dcfcc6ce 100644
--- a/lib/acyclicGraph.ml
+++ b/lib/acyclicGraph.ml
@@ -721,7 +721,10 @@ module Make (Point:Point) = struct
     let rmap, csts = PSet.fold (fun u (rmap,csts) ->
         let arcu = repr g u in
         if PSet.mem arcu.canon kept then
-          PMap.add arcu.canon arcu.canon rmap, Constraint.add (u,Eq,arcu.canon) csts
+          let csts = if Point.equal u arcu.canon then csts
+            else Constraint.add (u,Eq,arcu.canon) csts
+          in
+          PMap.add arcu.canon arcu.canon rmap, csts
         else
           match PMap.find arcu.canon rmap with
           | v -> rmap, Constraint.add (u,Eq,v) csts
-- 
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