From da6c1744707bd10ae02a34a4446727606d5223d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mihnea=20R=C4=83dulescu?=
 <29178174+mihnea-radulescu@users.noreply.github.com>
Date: Tue, 14 May 2024 15:13:02 +0300
Subject: [PATCH] Arg.Any<Arg.AnyType>() does not match arguments passed by
 reference (#787) (#811)
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Content-Transfer-Encoding: 8bit

Co-authored-by: Mihnea Rădulescu <>
---
 src/NSubstitute/Core/CallSpecification.cs       | 11 ++++++++---
 .../ReceivedCalls.cs                            | 17 +++++++++++++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/NSubstitute/Core/CallSpecification.cs b/src/NSubstitute/Core/CallSpecification.cs
index 0dfa04cf..b0018439 100644
--- a/src/NSubstitute/Core/CallSpecification.cs
+++ b/src/NSubstitute/Core/CallSpecification.cs
@@ -77,7 +77,7 @@ internal static bool TypesAreAllEquivalent(Type[] aArgs, Type[] bArgs)
             if (first.IsGenericType && second.IsGenericType
                 && first.GetGenericTypeDefinition() == second.GetGenericTypeDefinition())
             {
-                // both are the same generic type. If their GenericTypeArguments match then they are equivalent 
+                // both are the same generic type. If their GenericTypeArguments match then they are equivalent
                 if (!TypesAreAllEquivalent(first.GenericTypeArguments, second.GenericTypeArguments))
                 {
                     return false;
@@ -85,8 +85,13 @@ internal static bool TypesAreAllEquivalent(Type[] aArgs, Type[] bArgs)
                 continue;
             }
 
-            var areEquivalent = first.IsAssignableFrom(second) || second.IsAssignableFrom(first) ||
-                                typeof(Arg.AnyType).IsAssignableFrom(first) || typeof(Arg.AnyType).IsAssignableFrom(second);
+            var areAssignable = first.IsAssignableFrom(second) || second.IsAssignableFrom(first);
+            var areAnyTypeAssignable = typeof(Arg.AnyType).IsAssignableFrom(first) ||
+                                       typeof(Arg.AnyType).IsAssignableFrom(second);
+            var areByRefAnyTypeAssignable = first.IsByRef && second.IsByRef &&
+                                            (typeof(Arg.AnyType).IsAssignableFrom(first.GetElementType()) ||
+                                             typeof(Arg.AnyType).IsAssignableFrom(second.GetElementType()));
+            var areEquivalent = areAssignable || areAnyTypeAssignable || areByRefAnyTypeAssignable;
             if (!areEquivalent) return false;
         }
         return true;
diff --git a/tests/NSubstitute.Acceptance.Specs/ReceivedCalls.cs b/tests/NSubstitute.Acceptance.Specs/ReceivedCalls.cs
index 3edbe6ff..4a664d9d 100644
--- a/tests/NSubstitute.Acceptance.Specs/ReceivedCalls.cs
+++ b/tests/NSubstitute.Acceptance.Specs/ReceivedCalls.cs
@@ -316,6 +316,16 @@ public void Throw_when_negative_min_range_given()
         StringAssert.Contains("minInclusive must be >= 0, but was -1.", ex.Message);
     }
 
+    [Test]
+    public void Works_with_byref_generic_parameters()
+    {
+        IMyService service = Substitute.For<IMyService>();
+        MyArgument arg = new();
+        service.MyMethod(ref arg);
+
+        service.Received().MyMethod(ref Arg.Any<Arg.AnyType>());
+    }
+
     public interface ICar
     {
         void Start();
@@ -329,4 +339,11 @@ public interface ICar
         float GetCapacityInLitres();
         event Action Started;
     }
+
+    public interface IMyService
+    {
+        void MyMethod<T>(ref T argument);
+    }
+
+    public class MyArgument { }
 }
\ No newline at end of file