Exclude ExplicitInterfaceImplementation methods

src/Orleans.CodeGenerator/Model/ProxyInterfaceDescription.cs

@@ -79,6 +79,14 @@ private List<ProxyMethodDescription> GetMethods()
             {
                 foreach (var method in iface.GetDeclaredInstanceMembers<IMethodSymbol>())
                 {
+                    if (method.MethodKind == MethodKind.ExplicitInterfaceImplementation)
+                    {
+                        // Explicit implementations can be ignored when generating a proxy.
+                        // Proxies must implement every method explicitly to ensure faithful reproduction of the interface behavior.
+                        // At the calling side, the explicit implementation will be called if it was not overridden by a derived type.
+                        continue;
+                    }
+
                     var methodDescription = CodeGenerator.GetProxyMethodDescription(InterfaceType, method: method);
                     result.Add(methodDescription);
                 }

test/DefaultCluster.Tests/CodeGenTests/IRuntimeCodeGenGrain.cs

@@ -8,6 +8,28 @@ namespace Tester.CodeGenTests
     using Orleans;
     using Orleans.Providers;
 
+    public interface ISomeInterface<in T>
+    {
+        Task M(T arg);
+    }
+
+    public interface IBase : ISomeInterface<object>;
+
+    public interface IDerived : IBase, ISomeInterface<string>
+    {
+        Task ISomeInterface<object>.M(object obj) => M(obj);
+    }
+
+    public interface ISomeGrainWithExplicitImplementation : IDerived, IGrainWithGuidKey;
+
+    public class SomeGrain : Grain, ISomeGrainWithExplicitImplementation
+    {
+        public Task M(string arg)
+        {
+            throw new NotImplementedException();
+        }
+    }
+
     public interface IGrainWithGenericMethods : IGrainWithGuidKey
     {
         Task<Type[]> GetTypesExplicit<T, U, V>();