[Jevan Saks (jevansaks)]

Summary

Resolve interface references through the existing qualified metadata resolver, using the defining generator and reader for both interface classification and COM ancestry. This preserves native interface pointers when a field's COM interface moves to another input WinMD.

For example, DML_BUFFER_BINDING.Buffer must remain ID3D12Resource* with allowMarshaling: false when Direct3D 12 interfaces are supplied by SDK-owned metadata instead of Windows metadata. Previously the external reference was classified as a non-interface and projected by value, failing a pointer assignment with CS0029.

The reader-ownership correction also covers marshaled interface arrays, transitive external non-COM ancestry, and inherited method inspection for COM callable wrappers. It does not change public APIs or production metadata inputs.

Regression coverage

Two small authored IL/WinMD fixtures use reciprocal assembly references. They cover local and external COM fields, marshaled COM arrays, native double pointers, and transitive external non-COM ancestry.

All three modes are exercised: native pointers (allowMarshaling: false), runtime marshaling, and AOT-compatible COM source generation. GUID-bearing interfaces allow the tests to run the .NET SDK's actual COM source generators on the projected code, check generator diagnostics, and compile/emit the completed output. Source-generated binding fields accept the native IExternalCom_unmanaged* projection; runtime-marshaled fields accept the managed interface.

Validation

• All 154 cases in COMTests and MultiMetadataTests pass, including six reciprocal-fixture cases across the three modes.
• Both generator legs build without warnings.
• The real minimal DML_BUFFER_BINDING consumer passes with baseline Windows metadata using CsWin32 0.3.367, and fails with CS0029 using the reciprocal Windows/D3D metadata pair.
• The unchanged native consumer builds with zero warnings/errors against baseline Windows metadata and the real reciprocal pair using the rebuilt generator. The reciprocal pair also passes using the rebuilt Roslyn 4.11 leg.
• The real reciprocal Windows/D3D consumer requesting DML_BUFFER_BINDING and DMLCreateDevice builds with zero warnings/errors in native, runtime-marshaled, and COM source-generated modes using the rebuilt build task. The source-generated case runs the SDK COM generator with IsAotCompatible and DisableRuntimeMarshalling enabled; Buffer accepts ID3D12Resource_unmanaged*.

This fixes a projection prerequisite for moving Direct3D 12 metadata ownership. Enabling Windows metadata removal still requires published fixed CsWin32 and WinmdGenerator releases and the coordinated SDK/package updates; this PR does not enable that removal.