[GeneratedComInterface] Add unsafe to derived partial interface when base has unsafe methods

src/libraries/System.Runtime.InteropServices/gen/ComInterfaceGenerator/ComInterfaceGenerator.cs

@@ -150,11 +150,7 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                     GenerateImplementationInterface(x, ct).NormalizeWhitespace(),
                     GenerateInterfaceImplementationVtable(x, ct).NormalizeWhitespace(),
                     GenerateImplementationVTableMethods(x, ct).NormalizeWhitespace(),
-                    x.Interface.Info.TypeDefinitionContext.WrapMemberInContainingSyntaxWithUnsafeModifier(TypeDeclaration(x.Interface.Info.ContainingSyntax.TypeKind, x.Interface.Info.ContainingSyntax.Identifier)
-                        .WithModifiers(x.Interface.Info.ContainingSyntax.Modifiers)
-                        .WithTypeParameterList(x.Interface.Info.ContainingSyntax.TypeParameters)
-                        .WithMembers(List<MemberDeclarationSyntax>(x.ShadowingMethods.Select(m => m.Shadow))))
-                        .NormalizeWhitespace(),
+                    GenerateShadowingMethodsInterface(x),
                     GenerateImplementationVTable(x, ct).NormalizeWhitespace(),
                     GenerateInterfaceInformation(x.Interface.Info, ct).NormalizeWhitespace(),
                     GenerateIUnknownDerivedAttributeApplication(x.Interface.Info, ct).NormalizeWhitespace()
@@ -231,6 +227,17 @@ private static MemberDeclarationSyntax GenerateIUnknownDerivedAttributeApplicati
                     .WithTypeParameterList(context.ContainingSyntax.TypeParameters)
                     .AddAttributeLists(AttributeList(SingletonSeparatedList(s_iUnknownDerivedAttributeTemplate))));
 
+        private static MemberDeclarationSyntax GenerateShadowingMethodsInterface(ComInterfaceAndMethodsContext interfaceMethods)
+        {
+            var containingSyntax = interfaceMethods.Interface.Info.ContainingSyntax;
+            return interfaceMethods.Interface.Info.TypeDefinitionContext.WrapMemberInContainingSyntaxWithUnsafeModifier(
+                TypeDeclaration(containingSyntax.TypeKind, containingSyntax.Identifier)
+                    .WithModifiers(containingSyntax.Modifiers.AddToModifiers(SyntaxKind.UnsafeKeyword))
+                    .WithTypeParameterList(containingSyntax.TypeParameters)
+                    .WithMembers(List<MemberDeclarationSyntax>(interfaceMethods.ShadowingMethods.Select(m => m.Shadow))))
+                    .NormalizeWhitespace();
+        }
+
         private static bool IsHResultLikeType(ManagedTypeInfo type)
         {
             string typeName = type.FullTypeName.Split('.', ':')[^1];

src/libraries/System.Runtime.InteropServices/tests/ComInterfaceGenerator.Unit.Tests/CodeSnippets.cs

@@ -701,6 +701,25 @@ unsafe partial interface INativeDerived : INativeAPIBase
             }
             """;
 
+        public string DerivedComInterfaceTypeWithUnsafeBaseMethod => $$"""
+            using System.Runtime.CompilerServices;
+            using System.Runtime.InteropServices;
+            using System.Runtime.InteropServices.Marshalling;
+
+            [assembly:DisableRuntimeMarshalling]
+
+            {{GeneratedComInterface()}}
+            partial interface IComInterfaceBase
+            {
+                unsafe void Method(void* pBuffer);
+            }
+            {{GeneratedComInterface()}}
+            partial interface IComInterfaceDerived : IComInterfaceBase
+            {
+                void Method2();
+            }
+            """;
+
         public class ManagedToUnmanaged : IVirtualMethodIndexSignatureProvider
         {
             public MarshalDirection Direction => MarshalDirection.ManagedToUnmanaged;

src/libraries/System.Runtime.InteropServices/tests/ComInterfaceGenerator.Unit.Tests/Compiles.cs

@@ -350,6 +350,7 @@ public static IEnumerable<object[]> ComInterfaceSnippetsToCompile()
             yield return new object[] { ID(), codeSnippets.ForwarderWithPreserveSigAndRefKind("in") };
             yield return new object[] { ID(), codeSnippets.ForwarderWithPreserveSigAndRefKind("out") };
             yield return new object[] { ID(), codeSnippets.ComInterfaceWithNativeMarshalling };
+            yield return new object[] { ID(), codeSnippets.DerivedComInterfaceTypeWithUnsafeBaseMethod };
         }
 
         public static IEnumerable<object[]> ManagedToUnmanagedComInterfaceSnippetsToCompile()