From 95053af1fcf7294d18b02d61fc915027be9e4aec Mon Sep 17 00:00:00 2001
From: Marco Persson <marcop@unity3d.com>
Date: Fri, 18 Nov 2022 11:06:44 +0100
Subject: [PATCH] Fix that method resolution would consider all
 function-pointers to be the same

---
 Mono.Cecil/MetadataResolver.cs       | 29 +++++++++++++++++
 Test/Mono.Cecil.Tests/MethodTests.cs | 47 +++++++++++++++++++++++++++-
 Test/Resources/il/others.il          | 17 +++++++++-
 3 files changed, 91 insertions(+), 2 deletions(-)

diff --git a/Mono.Cecil/MetadataResolver.cs b/Mono.Cecil/MetadataResolver.cs
index 95d900726..5288006c6 100644
--- a/Mono.Cecil/MetadataResolver.cs
+++ b/Mono.Cecil/MetadataResolver.cs
@@ -334,6 +334,35 @@ static bool AreSame (TypeSpecification a, TypeSpecification b)
 			if (a.IsArray)
 				return AreSame ((ArrayType) a, (ArrayType) b);
 
+			if (a.IsFunctionPointer)
+				return AreSame ((FunctionPointerType) a, (FunctionPointerType) b);
+
+			return true;
+		}
+
+		static bool AreSame (FunctionPointerType a, FunctionPointerType b)
+		{
+			if (a.HasThis != b.HasThis)
+				return false;
+			
+			if (a.CallingConvention != b.CallingConvention)
+				return false;
+
+			if (!AreSame (a.ReturnType, b.ReturnType))
+				return false;
+
+			if (a.ContainsGenericParameter != b.ContainsGenericParameter)
+				return false;
+
+			if (a.HasParameters != b.HasParameters)
+				return false;
+
+			if (!a.HasParameters)
+				return true;
+
+			if (!AreSame (a.Parameters, b.Parameters))
+				return false;
+			
 			return true;
 		}
 
diff --git a/Test/Mono.Cecil.Tests/MethodTests.cs b/Test/Mono.Cecil.Tests/MethodTests.cs
index cef897dd2..8a3fa1286 100644
--- a/Test/Mono.Cecil.Tests/MethodTests.cs
+++ b/Test/Mono.Cecil.Tests/MethodTests.cs
@@ -3,7 +3,7 @@
 
 using Mono.Cecil;
 using Mono.Cecil.Metadata;
-
+using Mono.Collections.Generic;
 using NUnit.Framework;
 
 namespace Mono.Cecil.Tests {
@@ -236,5 +236,50 @@ public void InstanceAndStaticMethodComparison ()
 				Assert.AreNotEqual(instance_method, static_method_reference.Resolve ());
 			});
 		}
+
+		[Test]
+		public void FunctionPointerArgumentOverload ()
+		{
+			TestIL ("others.il", module => {
+				var others = module.GetType ("Others");
+				var overloaded_methods = others.Methods.Where (m => m.Name == "OverloadedWithFpArg").ToArray ();
+				// Manually create the function-pointer type so `AreSame` won't exit early due to reference equality
+				var overloaded_method_int_reference = new MethodReference ("OverloadedWithFpArg", module.TypeSystem.Void, others) 
+				{
+					HasThis = false,
+					Parameters = { new ParameterDefinition ("X", ParameterAttributes.None, new FunctionPointerType () {
+						HasThis = false,
+						ReturnType = module.TypeSystem.Int32,
+						Parameters = { new ParameterDefinition (module.TypeSystem.Int32) }
+					}) }
+				};
+				
+				var overloaded_method_long_reference = new MethodReference ("OverloadedWithFpArg", module.TypeSystem.Void, others) 
+				{
+					HasThis = false,
+					Parameters = { new ParameterDefinition ("X", ParameterAttributes.None, new FunctionPointerType () {
+						HasThis = false,
+						ReturnType = module.TypeSystem.Int32,
+						Parameters = { new ParameterDefinition (module.TypeSystem.Int64) }
+					}) }
+				};
+				
+				var overloaded_method_cdecl_reference = new MethodReference ("OverloadedWithFpArg", module.TypeSystem.Void, others) 
+				{
+					HasThis = false,
+					Parameters = { new ParameterDefinition ("X", ParameterAttributes.None, new FunctionPointerType () {
+						CallingConvention = MethodCallingConvention.C,
+						HasThis = false,
+						ReturnType = module.TypeSystem.Int32,
+						Parameters = { new ParameterDefinition (module.TypeSystem.Int32) }
+					}) } 
+				};
+				
+
+				Assert.AreEqual (overloaded_methods[0], overloaded_method_int_reference.Resolve ()); 
+				Assert.AreEqual (overloaded_methods[1], overloaded_method_long_reference.Resolve ()); 
+				Assert.AreEqual (overloaded_methods[2], overloaded_method_cdecl_reference.Resolve ()); 
+			});
+		}
 	}
 }
diff --git a/Test/Resources/il/others.il b/Test/Resources/il/others.il
index 22691a2d2..7be104208 100644
--- a/Test/Resources/il/others.il
+++ b/Test/Resources/il/others.il
@@ -78,7 +78,22 @@
 		.other instance void Others::dang_Handler (class [mscorlib]System.EventHandler)
 		.other instance void Others::fang_Handler (class [mscorlib]System.EventHandler)
 	}
-	
+
+	.method public static void OverloadedWithFpArg(method int32 *(int32) X) cil managed
+	{
+	    ret
+	}
+
+	.method public static void OverloadedWithFpArg(method int32 *(int64) X) cil managed
+	{
+	    ret
+	}
+
+	.method public static void OverloadedWithFpArg(method unmanaged cdecl int32 *(int32) X) cil managed
+	{
+	    ret
+	}
+
 	.method public instance void  SameMethodNameInstanceStatic() cil managed
 	{
 		ret