From 6e2ffc5e8c8871e44af00b129b48039f959a18c9 Mon Sep 17 00:00:00 2001
From: Stewart Allen <stewart.allen@gmail.com>
Date: Thu, 29 Apr 2021 12:21:01 -0400
Subject: [PATCH] fix rare union fail with deadlock

---
 src/geo/polygon.js | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/geo/polygon.js b/src/geo/polygon.js
index 9823d2de..30581f60 100644
--- a/src/geo/polygon.js
+++ b/src/geo/polygon.js
@@ -1781,6 +1781,10 @@
                     if (src[0].isEquivalent(dst[0]) && src[1].isEquivalent(dst[1])) {
                         return null;
                     }
+                    // only here is area sorting failed (same sizes)
+                    if (src[0].isEquivalent(dst[1]) && src[1].isEquivalent(dst[0])) {
+                        return null;
+                    }
                 }
                 return union;
             }