Magical ???default??? interface implementation in managed c++ dll

[Bob]

Problem: Why does my Managed C++ class library seem to have a default
implementation when implementing an interface definition I got from an
interop assembly I generated from my VC++7.1 COM component?

I would expect the DLL to not compile without having actually implemented
the interface's methods on my __gc class, but it compiles fine??? When I
look in ILDASM, it seems to already have a default implementation. If I
actually provide an implementation on the mc++ class, ILDASM shows both
implementations. When you do this in C#, it doesn't compile if not
implemented and it only has the one implementation when viewing in ILDASM.

Can someone explain what is going on? I am very familiar with COM Interop
and and have done numerous things from COM to C# and vice versa. I generated
the interop assembly by hand using tlbimp.exe, and I can reference it fine
and browse fine, so I hope this is simply operator error from a mc++
standpoint.

Thanks,
--
Bob
Sr. Microsoft Architect
Lighthammer Software