Bug: compiler error when inheriting from DataTemplateSelectorT

[dlech]

Version

2.0.240405.15

Summary

There is a compiler error due to code generated by cppwinrt when trying to use winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT as a base class.

Reproducible example

struct Example : DataTemplateSelectorT<Example>
{
};

Grab the project from https://github.com/dlech/BlankApp1, open in Visual Studio and build.

Code that causes the problem is here: https://github.com/dlech/BlankApp1/blob/d2869cb888d4d67534ba76643816a15bfa0274c8/BlankApp1/App.cpp#L16-L18

Expected behavior

cppwrint should generate code that doesn't cause a compile error.

Actual behavior

Build fails with the following error:

1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66450,9): error C2602: 'winrt::impl::consume_Windows_UI_Xaml_Controls_IDataTemplateSelectorOverrides<D>::SelectTemplateCore' is not a member of a base class of 'winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<Example>'
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66450,9): error C2602:         with
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66450,9): error C2602:         [
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66450,9): error C2602:             D=Example
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66450,9): error C2602:         ]
1>(compiling source file '/App.cpp')
1>    C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\impl\Windows.UI.Xaml.Controls.0.h(17492,14):
1>    see declaration of 'winrt::impl::consume_Windows_UI_Xaml_Controls_IDataTemplateSelectorOverrides<D>::SelectTemplateCore'
1>        with
1>        [
1>            D=Example
1>        ]
1>    C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66436,12):
1>    see declaration of 'winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<Example>'
1>    C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66450,9):
1>    the template instantiation context (the oldest one first) is
1>        C:\Users\extra\source\repos\BlankApp1\BlankApp1\App.cpp(16,18):
1>        see reference to class template instantiation 'winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<Example>' being compiled
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66451,9): error C2602: 'winrt::impl::consume_Windows_UI_Xaml_Controls_IDataTemplateSelectorOverrides2<D>::SelectTemplateCore' is not a member of a base class of 'winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<Example>'
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66451,9): error C2602:         with
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66451,9): error C2602:         [
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66451,9): error C2602:             D=Example
1>C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66451,9): error C2602:         ]
1>(compiling source file '/App.cpp')
1>    C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\impl\Windows.UI.Xaml.Controls.0.h(17501,14):
1>    see declaration of 'winrt::impl::consume_Windows_UI_Xaml_Controls_IDataTemplateSelectorOverrides2<D>::SelectTemplateCore'
1>        with
1>        [
1>            D=Example
1>        ]
1>    C:\Users\extra\source\repos\BlankApp1\BlankApp1\Generated Files\winrt\Windows.UI.Xaml.Controls.h(66436,12):
1>    see declaration of 'winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<Example>'

Additional comments

I discovered this while working on the PyWinRT bindings. Using any other TypeT as a base class compiles fine. There seems to be something odd about winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT::SelectTemplateCore specially. It is likely the only type where it has two overloads with the same name and different parameters defined in two different interfaces.

[dlech]

The error from the reproducible test case says "is not a member of a base class of ", but I think this is actually a case of a ambiguous name. Here is the output from compiling some similar code with the clang compiler instead of msvc.

C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/Windows.UI.Xaml.Controls.h:66451:15: error: using declaration refers into 'impl::consume_t<python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>, winrt::Windows::UI::Xaml::Controls::IDataTemplateSelectorOverrides2>::', which is not a base class of 'DataTemplateSelectorT<py::python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>>'
 66451 |         using impl::consume_t<D, winrt::Windows::UI::Xaml::Controls::IDataTemplateSelectorOverrides2>::SelectTemplateCore;
       |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/Windows.UI.Xaml.Controls.h:31610:88: error: member 'SelectTemplateCore' found in multiple base classes of different types
 31610 |             *result = detach_from<winrt::Windows::UI::Xaml::DataTemplate>(this->shim().SelectTemplateCore(*reinterpret_cast<winrt::Windows::Foundation::IInspectable const*>(&item), *reinterpret_cast<winrt::Windows::UI::Xaml::DependencyObject const*>(&container)));   
       |                                                                                    
    ^
C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7255:12: note: in instantiation of member function 'winrt::impl::produce<py::python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>, winrt::Windows::UI::Xaml::Controls::IDataTemplateSelectorOverrides>::SelectTemplateCore' requested here
 7255 |     struct producer
      |            ^
C:/Users/extra/work/pywinrt/projection/winrt-Windows.UI.Xaml.Controls/py.Windows.UI.Xaml.Controls.cpp:105:83: note: in instantiation of member function 'winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<py::python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>>::DataTemplateSelectorT' requested here
  105 |         python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>() : winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>>() {}
      |                                                                                   ^ 
C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/impl/Windows.UI.Xaml.Controls.2.h:3504:14: note: member found by ambiguous name lookup
 3504 |         auto SelectTemplateCore(winrt::Windows::Foundation::IInspectable const& item, winrt::Windows::UI::Xaml::DependencyObject const& container) const;
      |              ^
C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/impl/Windows.UI.Xaml.Controls.2.h:3513:14: note: member found by ambiguous name lookup
 3513 |         auto SelectTemplateCore(winrt::Windows::Foundation::IInspectable const& item) const;
      |              ^
In file included from C:/Users/extra/work/pywinrt/projection/winrt-Windows.UI.Xaml.Controls/py.Windows.UI.Xaml.Controls.cpp:3:
In file included from C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/pywinrt/py.Windows.UI.Xaml.Controls.h:85:
In file included from C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/pywinrt/py.Windows.UI.Xaml.h:61:
In file included from C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/pywinrt/py.Windows.UI.Xaml.Controls.Primitives.h:33:
In file included from C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/pywinrt/py.Windows.UI.Xaml.Input.h:47:
C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/Windows.UI.Xaml.Controls.h:31622:88: error: member 'SelectTemplateCore' found in multiple base classes of different types
 31622 |             *result = detach_from<winrt::Windows::UI::Xaml::DataTemplate>(this->shim().SelectTemplateCore(*reinterpret_cast<winrt::Windows::Foundation::IInspectable const*>(&item)));
       |                                                                                    
    ^
C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/base.h:7255:12: note: in instantiation of member function 'winrt::impl::produce<py::python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>, winrt::Windows::UI::Xaml::Controls::IDataTemplateSelectorOverrides2>::SelectTemplateForItemCore' requested here
 7255 |     struct producer
      |            ^
C:/Users/extra/work/pywinrt/projection/winrt-Windows.UI.Xaml.Controls/py.Windows.UI.Xaml.Controls.cpp:105:83: note: in instantiation of member function 'winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<py::python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>>::DataTemplateSelectorT' requested here
  105 |         python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>() : winrt::Windows::UI::Xaml::Controls::DataTemplateSelectorT<python_impl<winrt::Windows::UI::Xaml::Controls::DataTemplateSelector>>() {}
      |                                                                                   ^ 
C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/impl/Windows.UI.Xaml.Controls.2.h:3504:14: note: member found by ambiguous name lookup
 3504 |         auto SelectTemplateCore(winrt::Windows::Foundation::IInspectable const& item, winrt::Windows::UI::Xaml::DependencyObject const& container) const;
      |              ^
C:/Users/extra/work/pywinrt/projection/winrt-sdk/src/winrt_sdk/cppwinrt/winrt/impl/Windows.UI.Xaml.Controls.2.h:3513:14: note: member found by ambiguous name lookup
 3513 |         auto SelectTemplateCore(winrt::Windows::Foundation::IInspectable const& item) const;
      |              ^
4 errors generated.

[sylveon]

Here's a smaller repro:

namespace RuntimeComponent2
{
    interface IClass;
    interface IClassFactory;
    interface IClassOverrides;
    interface IClassOverrides2;

    [exclusiveto(RuntimeComponent2.Class)]
    [uuid(A907D496-46A0-4CD7-8DBE-F9A581DF60B1)]
    [version(0x00000001)]
    interface IClass : IInspectable
    {
    }

    [exclusiveto(RuntimeComponent2.Class)]
    [uuid(511BAAD0-210A-457D-9521-433D2B11B7D2)]
    [version(0x00000001)]
    interface IClassFactory : IInspectable
    {
        HRESULT CreateInstance([in] IInspectable* baseInterface, [out] IInspectable** innerInterface, [out][retval] RuntimeComponent2.Class** value);
    }

    [exclusiveto(RuntimeComponent2.Class)]
    [uuid(2D162925-5966-4BFA-8638-4D345689F6CF)]
    [version(0x00000001)]
    interface IClassOverrides : IInspectable
    {
        HRESULT Foo(int a);
    }

    [exclusiveto(RuntimeComponent2.Class)]
    [uuid(6C3FB5FC-8E84-4C91-AC15-04A1D885500F)]
    [version(0x00000001)]
    interface IClassOverrides2 : IInspectable
    {
        [overload("Foo")] HRESULT Foo2(int a, int b);
    }

    [composable(RuntimeComponent2.IClassFactory, public,1)]
    [marshaling_behavior(agile)]
    [threading(both)]
    [version(0x00000001)]
    runtimeclass Class
    {
        [default] interface RuntimeComponent2.IClass;
        [overridable] interface RuntimeComponent2.IClassOverrides;
        [overridable] interface RuntimeComponent2.IClassOverrides2;
    }
}

It appears to be a bug in write_class_override_usings. If I remove [overload("Foo")] the two using are not created and the bug does not reproduce.

DataTemplateSelector appears to be the only case of this happening

[sylveon]

Opened #1458 with a fix. Was relatively trivial thankfully.

[dlech]

Wow, same day service! Thanks for having a look!

[sylveon]

Haha. I wanted to make sure it wasn't a regression introduced by a previous PR of mine, which was the last change to code touching overridable members.

Once I realized it was a bug in write_class_override_usings (which my PR didn't change, so it wasn't a regression) it became fairly obvious what the issue was.

The code was writing an using impl::consume_t for overloads that came from different interfaces, because otherwise you would get "ambiguous call" compiler errors. But when you use FooT to inherit from a WinRT class, any IFooOverridable interface isn't added by inheriting from consume_t<IFooOverridable> but from produce<IFooOverridable>. Just had to adjust the writer to compensate for this case :)

[github-actions]

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