erichkeane added a comment.
In https://reviews.llvm.org/D37308#858309, @zahiraam wrote:
> Aaron,
>
> Yes I want to this to succeed:
>
> struct __declspec(uuid("00000000-0000-0000-C000-000000000046")) IUnknown {};
> __interface ISfFileIOPropertyPage : public IUnknown {};
>
> But I also want this to succeed:
>
> struct __declspec(uuid("00000000-0000-0000-C000-000000000046")) IUnknown {};
> struct IPropertyPage : public IUnknown {};
> __interface ISfFileIOPropertyPage : public IPropertyPage {};
>
> And I can't figure out how these 2 can be differentiated. I think the
> conditions that I have currently are differently too. This later case doesn't
> succeed with the current code.
> And I want this to fail:
>
> class __declspec(uuid("00000000-0000-0000-C000-000000000046")) IUnknown1 {};
> __interface __declspec(dllimport) ISfFileIOPropertyPage1 : public IUnknown1
> {};
>
> This currently does with the current code.
>
> I guess I need to work on it a bit more.
It definitely looks like you'll have to walk the inheritance tree to get the
2nd example to work. Based on that, the rule seems to be, an __interface can
inherit from:
1 - Another __interface
2 - The COMPLETE IUnknown type, such that it is a struct, with a uuid of
000...C000...46, named "IUnknown", with an empty definition. (note that this is
independent of namespace)
3- Any other type that:
-a: is a class or struct
-b: has no members
-c: inherits from at least 1 type that:
--I: Is an IUnknown type (in any namespace) --or--
--II: A type that satisfies this point 3.
-d: Inherits from no types other than those in -c.
Note that multiple inheritance is permitted:
namespace S{
struct __declspec(uuid("00000000-0000-0000-C000-000000000046")) IUnknown {};
}
namespace S2{
struct __declspec(uuid("00000000-0000-0000-C000-000000000046")) IUnknown {};
}
class __declspec(deprecated("asdf")) IPropertyPage2 : S::IUnknown,
S2::IUnknown { }; // Inherits from 2 different IUnknowns
class __declspec(deprecated("asdf")) IPropertyPage3 : S::IUnknown,
S2::IUnknown { };
class IP3 : IPropertyPage2, IPropertyPage3 {}; // Inherits from 2 different
classes that meet #3 above.
https://reviews.llvm.org/D37308
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