Can't implement WinRT interfaces in a module partition

[jaigak]

Having exported classes in a module partition that implements WinRT interfaces by deriving from the winrt::implements class template doesn't seem to work and gives this error:

1>S:\ConsoleApplication1\ConsoleApplication1\x64\Debug\Generated Files\winrt\base.h(857,21): error C2676: binary '==': 'const winrt::guid' does not define this operator or a conversion to a type acceptable to the predefined operator
1>S:\ConsoleApplication1\ConsoleApplication1\x64\Debug\Generated Files\winrt\base.h(7206,1): message : see reference to function template instantiation 'bool winrt::is_guid_of<winrt::impl::IWeakReference>(const winrt::guid &) noexcept' being compiled
1>S:\ConsoleApplication1\ConsoleApplication1\x64\Debug\Generated Files\winrt\base.h(7205,1): message : while compiling class template member function 'int32_t winrt::impl::weak_ref<true,true>::QueryInterface(const winrt::guid &,void **) noexcept'
1>S:\ConsoleApplication1\ConsoleApplication1\x64\Debug\Generated Files\winrt\base.h(7613,1): message : see reference to class template instantiation 'winrt::impl::weak_ref<true,true>' being compiled
1>S:\ConsoleApplication1\ConsoleApplication1\x64\Debug\Generated Files\winrt\base.h(7604,1): message : while compiling class template member function 'uint32_t winrt::impl::root_implements<D,winrt::Windows::Foundation::IStringable>::subtract_final_reference(void) noexcept'
1>        with
1>        [
1>            D=Stringable
1>        ]
1>S:\ConsoleApplication1\ConsoleApplication1\x64\Debug\Generated Files\winrt\base.h(7446,37): message : see reference to function template instantiation 'uint32_t winrt::impl::root_implements<D,winrt::Windows::Foundation::IStringable>::subtract_final_reference(void) noexcept' being compiled
1>        with
1>        [
1>            D=Stringable
1>        ]
1>S:\ConsoleApplication1\ConsoleApplication1\x64\Debug\Generated Files\winrt\base.h(7979,1): message : see reference to class template instantiation 'winrt::impl::root_implements<D,winrt::Windows::Foundation::IStringable>' being compiled
1>        with
1>        [
1>            D=Stringable
1>        ]
1>S:\ConsoleApplication1\ConsoleApplication1\Module.ixx(3,1): message : see reference to class template instantiation 'winrt::implements<Stringable,winrt::Windows::Foundation::IStringable>' being compiled
1>S:\ConsoleApplication1\ConsoleApplication1\x64\Debug\Generated Files\winrt\base.h(857,21): error C2088: '==': illegal for struct

Source

Remember to disable precompiled headers first.

Module.ixx

export module Module;

export import :WinRT;

Module-WinRT.ixx

module;

#include <winrt/Windows.Foundation.h>

export module Module:WinRT;

using namespace winrt;

export struct Stringable : implements<Stringable, Windows::Foundation::IStringable>
{
	hstring ToString()
	{
		return L"Hello for C++ modules!";
	}
};

[kennykerr]

Modules aren't supported. #953

[jaigak]

Looks like the error message goes away if the WinRT header containing the interface implemented (winrt/Windows.Foundation.h) is also included in the module interface unit (Module.ixx). Not sure why that's required, but works.

[YexuanXiao]

Hello everyone, I've added C++ module support to C++/WinRT and written a blog post about my journey. With my fork, you can reference the modules you need on demand, just like in C#. I've published it on NuGet with the ID YexuanXiao.CppWinRTPlus. The repository link is https://github.com/YexuanXiao/cppwinrtplus, and the blog post is at https://github.com/YexuanXiao/cppwinrtplus/blob/master/about_module.md. The project is currently in the experimental stage, and I hope you'll enjoy it. Welcome any bug reports, feature suggestions, and other feedback.