From 6ac6cd324805e137571b6e2b5321043f765afd2f Mon Sep 17 00:00:00 2001
From: Rolf Bjarne Kvinge <rolf@xamarin.com>
Date: Fri, 17 Jul 2020 16:38:40 +0200
Subject: [PATCH] [ObjCRuntime] Work around a difference in .NET where
 Type.IsInterface doesn't work the same for byref types.

Ref: https://github.com/dotnet/runtime/issues/39068
---
 src/ObjCRuntime/Runtime.cs | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/ObjCRuntime/Runtime.cs b/src/ObjCRuntime/Runtime.cs
index 529b16e7b255..0e6e2e797951 100644
--- a/src/ObjCRuntime/Runtime.cs
+++ b/src/ObjCRuntime/Runtime.cs
@@ -1358,7 +1358,14 @@ static Type LookupINativeObjectImplementation (IntPtr ptr, Type target_type, Typ
 				}
 			}
 
-			if (implementation.IsInterface)
+			var interface_check_type = implementation;
+#if NET
+				// https://github.com/dotnet/runtime/issues/39068
+				if (interface_check_type.IsByRef)
+					interface_check_type = interface_check_type.GetElementType ();
+#endif
+
+			if (interface_check_type.IsInterface) 
 				implementation = FindProtocolWrapperType (implementation);
 
 			return implementation;
@@ -1382,8 +1389,14 @@ static INativeObject GetINativeObject (IntPtr ptr, bool owns, Type target_type,
 			}
 
 			if (o != null) {
+				var interface_check_type = target_type;
+#if NET
+				// https://github.com/dotnet/runtime/issues/39068
+				if (interface_check_type.IsByRef)
+					interface_check_type = interface_check_type.GetElementType ();
+#endif
 				// found an existing object, but with an incompatible type.
-				if (!target_type.IsInterface) {
+				if (!interface_check_type.IsInterface) {
 					// if the target type is another class, there's nothing we can do.
 					throw new InvalidCastException (string.Format ("Unable to cast object of type '{0}' to type '{1}'.", o.GetType ().FullName, target_type.FullName));
 				}
@@ -1456,6 +1469,12 @@ public static T GetINativeObject<T> (IntPtr ptr, bool forced_type, bool owns) wh
 
 		private static Type FindProtocolWrapperType (Type type)
 		{
+#if NET
+			// https://github.com/dotnet/runtime/issues/39068
+			if (type.IsByRef) {
+				type = type.GetElementType ();
+			}
+#endif
 			if (type == null || !type.IsInterface)
 				return null;