[Issue 12607] Document that IUnknown classes must mark toString with extern(D) when overriding it

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12607

--- Comment #4 from Steven Schveighoffer <schveiguy at yahoo.com> ---
(In reply to Andrej Mitrovic from comment #3)
> The only problem is, how do you call toString via an IUnknown interface?

You can't. Because the layout of IUnknown interfaces MUST follow COM, the RTTI
link to D's typeinfo system is missing. Remember that a proper D interface has
a mechanism of defining how to find the object start (and therefore the
vtable). An IUnknown interface does not have that.

Note that an IUnknown object may not even be a D object!

Once you go into IUnknown land, there's no coming back out (bwahahaha!)

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