Fix building proxies for classess with static interface members (#3298)

Fixes #3295

src/NHibernate.Test/StaticProxyTest/StaticProxyFactoryFixture.cs

@@ -816,6 +816,50 @@ private static BinaryFormatter GetFormatter()
 #endif
 		}
 
+#if NETCOREAPP3_1_OR_GREATER
+		public interface IWithStaticMethods
+		{
+			// C# 8
+			static void StaticMethod()
+			{
+			}
+
+#if NET7_0_OR_GREATER
+			// C# 11
+			static abstract void StaticAbstractMethod();
+
+			// C# 11
+			static virtual void StaticVirtualMethod()
+			{
+			}
+#endif
+		}
+
+		public class ClassWithStaticInterfaceMethods : IWithStaticMethods
+		{
+			public static void StaticAbstractMethod()
+			{
+			}
+		}
+
+		[Test(Description = "GH3295")]
+		public void VerifyProxyForClassWithStaticInterfaceMethod()
+		{
+			var factory = new StaticProxyFactory();
+			factory.PostInstantiate(
+				typeof(ClassWithStaticInterfaceMethods).FullName,
+				typeof(ClassWithStaticInterfaceMethods),
+				new HashSet<System.Type> { typeof(INHibernateProxy) },
+				null, null, null, true);
+
+			var proxy = factory.GetProxy(1, null);
+			Assert.That(proxy, Is.Not.Null);
+			Assert.That(proxy, Is.InstanceOf<ClassWithStaticInterfaceMethods>());
+
+			Assert.That(factory.GetFieldInterceptionProxy(), Is.InstanceOf<ClassWithStaticInterfaceMethods>());
+		}
+#endif
+
 #if NETFX
 		private static void VerifyGeneratedAssembly(System.Action assemblyGenerator)
 		{

src/NHibernate/Proxy/ProxyBuilderHelper.cs

@@ -21,6 +21,8 @@ namespace NHibernate.Proxy
 {
 	internal static class ProxyBuilderHelper
 	{
+		private const BindingFlags ProxiableMethodsBindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
+
 		private static readonly ConstructorInfo ObjectConstructor = typeof(object).GetConstructor(System.Type.EmptyTypes);
 		private static readonly ConstructorInfo SecurityCriticalAttributeConstructor = typeof(SecurityCriticalAttribute).GetConstructor(System.Type.EmptyTypes);
 		private static readonly ConstructorInfo IgnoresAccessChecksToAttributeConstructor = typeof(IgnoresAccessChecksToAttribute).GetConstructor(new[] {typeof(string)});
@@ -94,23 +96,20 @@ internal static void CallDefaultBaseConstructor(ILGenerator il, System.Type pare
 
 		internal static IEnumerable<MethodInfo> GetProxiableMethods(System.Type type)
 		{
-			const BindingFlags candidateMethodsBindingFlags =
-				BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
-
-			return type.GetMethods(candidateMethodsBindingFlags).Where(m => m.IsProxiable());
+			return type.GetMethods(ProxiableMethodsBindingFlags).Where(m => m.IsProxiable());
 		}
 
 		internal static IEnumerable<MethodInfo> GetProxiableMethods(System.Type type, IEnumerable<System.Type> interfaces)
 		{
 			if (type.IsInterface || type == typeof(object) || type.GetInterfaces().Length == 0)
 			{
 				return GetProxiableMethods(type)
-					.Concat(interfaces.SelectMany(i => i.GetMethods()))
+					.Concat(interfaces.SelectMany(i => i.GetMethods(ProxiableMethodsBindingFlags)))
 					.Distinct();
 			}
 
 			var proxiableMethods = new HashSet<MethodInfo>(GetProxiableMethods(type), new MethodInfoComparer(type));
-			foreach (var interfaceMethod in interfaces.SelectMany(i => i.GetMethods()))
+			foreach (var interfaceMethod in interfaces.SelectMany(i => i.GetMethods(ProxiableMethodsBindingFlags)))
 			{
 				proxiableMethods.Add(interfaceMethod);
 			}