Cannot compile WinUI 3.0 app that references a custom Windows Runtime component - winrt-xaml

Question

I have a Visual Studio 2019 solution that contains two project.
The first project has been created using the "Windows Runtime Component (WinUI 3) Visual Studio template (library project). It generates a dll and associated winmd file that contains a DirectX-based Windows Runtime component to be used in the user interface of a WinUI 3.0 app.
The second project has been created using the "Blank App, Packaged (WinUI 3 in Desktop)" Visual Studio template. It generates a Win32 app that utilizes WinUI 3.0 as the UI framework and consumes the output of the first project.
That second project references the first project via Visual Studio / MSBuild project reference.
The first project defines the component via MIDL as follows:
namespace My.Company.Name.DirectX
{
runtimeclass CustomControl : Microsoft.UI.Xaml.Controls.SwapChainPanel
{
CustomControl();
// All interface methods and properties
}
}
The header that gets generated form this looks as follows:
namespace winrt::My::Company::Name::DirectX::implementation
{
struct CustomControl : CustomControlT<CustomControl>
{
public:
CustomControl();
~CustomControl();
// // All interface methods and properties
};
}
namespace winrt::My::Company::Name::DirectX::factory_implementation
{
struct CustomControl : CustomControlT<CustomControl, implementation::CustomControl>
{
};
}
I then attempt to use that component within a Microsoft.UI.Xaml.Controls.Page XAML file as follows:
<Page
x:Class="My.Company.Name.App.CustomControlPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:My.Company.Name.App"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:Controls="using:My.Company.Name.DirectX"
mc:Ignorable="d">
<Controls:CustomControl/>
</Page>
However, if I compile the entire code I get the following error messages:
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(29,46): error C3083: 'DirectX': the symbol to the left of a '::' must be a type (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(145): message : see reference to class template instantiation 'winrt::My::Company::Name::App::implementation::CustomControlPageT<D,I...>' being compiled (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(29,55): error C2039: 'CustomControl': is not a member of 'winrt::My::Company::Name' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(10): message : see declaration of 'winrt::My::Company::Name' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(29,66): error C3646: 'CustomControl': unknown override specifier (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(29,76): error C2059: syntax error: '(' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(30,1): error C2334: unexpected token(s) preceding '{'; skipping apparent function body (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(33,62): error C3083: 'DirectX': the symbol to the left of a '::' must be a type (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(33,71): error C2039: 'CustomControl': is not a member of 'winrt::My::Company::Name' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(10): message : see declaration of 'winrt::My::Company::Name' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(33,1): error C2061: syntax error: identifier 'CustomControl' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(134,46): error C3083: 'DirectX': the symbol to the left of a '::' must be a type (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(134,55): error C2039: 'CustomControl': is not a member of 'winrt::My::Company::Name' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(10): message : see declaration of 'winrt::My::Company::Name' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(134,66): error C3646: '_CustomControl': unknown override specifier (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(134,77): error C2059: syntax error: '{' (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(134,1): error C2334: unexpected token(s) preceding '{'; skipping apparent function body (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(35,13): error C3861: '_CustomControl': identifier not found (compiling source file Page\CustomControlPage.cpp)
My.Company.Name.App\Generated Files\Page\CustomControlPage.xaml.g.h(35,27): error C3861: 'value': identifier not found (compiling source file Page\CustomControlPage.cpp)
Somehow, my CustomControl is not recognized when compiling the source code that is generated for the XAML file that references it. I don't understand what the problem is. In theory, all I that is required to use that component is the winmd file because it should describe that component.
Can someone tell me why I'm getting these errors?
Edit:
I have attempted to reproduce the problem and the resulting Git repository is available here