From 13dc5032526bc06c0efc8afc00c5bfe80f1d6e63 Mon Sep 17 00:00:00 2001
From: philstopford <phil.stopford@gmail.com>
Date: Sun, 11 Sep 2022 08:50:16 -0400
Subject: [PATCH] Make struct read-only (#220)

Also address warning about Equals override not matching nullability.
---
 CSharp/Clipper2Lib/Clipper.Engine.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/CSharp/Clipper2Lib/Clipper.Engine.cs b/CSharp/Clipper2Lib/Clipper.Engine.cs
index 7a2cadc3..b4c28ca4 100644
--- a/CSharp/Clipper2Lib/Clipper.Engine.cs
+++ b/CSharp/Clipper2Lib/Clipper.Engine.cs
@@ -62,7 +62,7 @@ public Vertex(Point64 pt, VertexFlags flags, Vertex? prev)
     }
   };
 
-  internal struct LocalMinima
+  internal readonly struct LocalMinima
   {
     public readonly Vertex vertex;
     public readonly PathType polytype;
@@ -85,7 +85,7 @@ public LocalMinima(Vertex vertex, PathType polytype, bool isOpen = false)
       return !(lm1 == lm2);
     }
 
-    public override bool Equals(object obj)
+    public override bool Equals(object? obj)
     {
       return obj is LocalMinima minima && this == minima;
     }