XamlTypeInfo.g.cpp Implementation Type Referenced But Not #included

[Entangled-Logic]

I'm following this tutorial and the single property tutorial:

https://learn.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/binding-collection

I declare a simple runtimeclass in .idl and create the code, and everything builds fine. I want to bind a togglebutton DataTemplate to the string in the runtime class and a collection of the class to the ItemsSource of the associated ComboBox. But when I use the runtimeclass in idl as the template type T of IObservableCollection I get an error in XamlTypeInfo.g.cpp where the implementation type of the runtimeclass is being referenced but there is no header file included. It only happens when I use the runtimeclass as the template type T. The tutorial is basic and I'm really at a loss as to what I'm doing wrong.

idl

namespace Duality23
{
[bindable]
[default_interface]
runtimeclass UserFilter : Microsoft.UI.Xaml.Data.INotifyPropertyChanged
{
UserFilter();
String Filter;
Boolean Selected;
}
}

xaml

ComboBox x:Name="FilterList"
Foreground="Black"
ItemsSource="{x:Bind SourceItems, Mode=TwoWay}"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
Padding="3,3,3,3"
FontWeight="Medium"
FontSize="14"
ItemsControl.ItemTemplate
DataTemplate x:DataType="local:UserFilter"
TextBlock Text="{x:Bind Filter, Mode=OneWay}"
DataTemplate
ItemsControl.ItemTemplate
ComboBox

idl

import "UserFilter.idl";
namespace Duality23
{
[bindable]
[default_interface]
runtimeclass UserTypeFilter : Microsoft.UI.Xaml.Controls.UserControl
{
UserTypeFilter();
event Windows.Foundation.EventHandler--String-- FilterChanged;
Windows.Foundation.Collections.IObservableVector--UserFilter-- SourceItems;
String Header;
String Data;
}
}

Pretty simple.

errors

1>..\Generated Files\XamlTypeInfo.g.cpp(939,60): error C2039: 'UserFilter': is not a member of 'winrt::Duality23::implementation'
1>..\Generated Files\XamlTypeInfo.g.cpp(92): message : see declaration of 'winrt::Duality23::implementation'
1>..\Generated Files\XamlTypeInfo.g.cpp(939,70): error C2275: 'winrt::Duality23::UserFilter': expected an expression instead of a type
1>..\Generated Files\XamlTypeInfo.g.cpp(939,6): error C2440: 'initializing': cannot convert from 'overloaded-function' to 'winrt::Windows::Foundation::IInspectable (__cdecl *)(void)'
1>..\Generated Files\XamlTypeInfo.g.cpp(939,6): message : None of the functions with this name in scope match the target type
1>..\Generated Files\XamlTypeInfo.g.cpp(945,5): error C2078: too many initializers

[Entangled-Logic]

It was an internal issue with Visual Studio resolved when VS was restarted. [resolved]