Fix obtaining type handles of IDynamicInterfaceCastableImplementation

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/TypeMetadataNode.cs

@@ -132,6 +132,18 @@ public static void GetMetadataDependencies(ref DependencyList dependencies, Node
                 default:
                     Debug.Assert(type.IsDefType);
 
+                    // We generally postpone creating MethodTables until absolutely needed.
+                    // IDynamicInterfaceCastableImplementation is special in the sense that just obtaining a System.Type
+                    // (by e.g. browsing custom attribute metadata) gives the user enough to pass this to runtime APIs
+                    // that need a MethodTable. We don't have a legitimate type handle without the MethodTable. Other
+                    // kinds of APIs that expect a MethodTable have enough dataflow annotation to trigger warnings.
+                    // There's no dataflow annotations on the IDynamicInterfaceCastable.GetInterfaceImplementation API.
+                    if (type.IsInterface && ((MetadataType)type).IsDynamicInterfaceCastableImplementation())
+                    {
+                        dependencies ??= new DependencyList();
+                        dependencies.Add(nodeFactory.ReflectedType(type), "Reflected IDynamicInterfaceCastableImplementation");
+                    }
+
                     TypeDesc typeDefinition = type.GetTypeDefinition();
                     if (typeDefinition != type)
                     {

src/tests/nativeaot/SmokeTests/UnitTests/Interfaces.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Text;
 using System.Collections.Generic;
+using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Diagnostics.CodeAnalysis;
@@ -60,6 +61,7 @@ public static int Run()
         TestDefaultDynamicStaticNonGeneric.Run();
         TestDefaultDynamicStaticGeneric.Run();
         TestDynamicStaticGenericVirtualMethods.Run();
+        TestRuntime109496Regression.Run();
 
         return Pass;
     }
@@ -1890,4 +1892,57 @@ public static void Run()
             Console.WriteLine(s_entry.Enter1<SimpleCallStruct<object>>("One"));
         }
     }
+
+    class TestRuntime109496Regression
+    {
+        class CastableThing : IDynamicInterfaceCastable
+        {
+            RuntimeTypeHandle IDynamicInterfaceCastable.GetInterfaceImplementation(RuntimeTypeHandle interfaceType)
+                => Type.GetTypeFromHandle(interfaceType).GetCustomAttribute<TypeAttribute>().TheType.TypeHandle;
+            bool IDynamicInterfaceCastable.IsInterfaceImplemented(RuntimeTypeHandle interfaceType, bool throwIfNotImplemented)
+                => Type.GetTypeFromHandle(interfaceType).IsDefined(typeof(TypeAttribute));
+        }
+
+        [Type(typeof(IMyInterfaceImpl))]
+        interface IMyInterface
+        {
+            int Method();
+        }
+
+        [DynamicInterfaceCastableImplementation]
+        interface IMyInterfaceImpl : IMyInterface
+        {
+            int IMyInterface.Method() => 42;
+        }
+
+        [Type(typeof(IMyGenericInterfaceImpl<int>))]
+        interface IMyGenericInterface
+        {
+            int Method();
+        }
+
+        [DynamicInterfaceCastableImplementation]
+        interface IMyGenericInterfaceImpl<T> : IMyGenericInterface
+        {
+            int IMyGenericInterface.Method() => typeof(T).Name.Length;
+        }
+
+        class TypeAttribute : Attribute
+        {
+            public Type TheType { get; }
+
+            public TypeAttribute(Type t) => TheType = t;
+        }
+
+        public static void Run()
+        {
+            object o = new CastableThing();
+
+            if (((IMyInterface)o).Method() != 42)
+                throw new Exception();
+
+            if (((IMyGenericInterface)o).Method() != 5)
+                throw new Exception();
+        }
+    }
 }