Inheriting from a XAML page within the same project fails to compile in C++/WinRT with /std:c++20

Describe the bug After upgrading to VS 17.0 Preview 2, inheriting from another XAML page within the same project results in a compile error when combined with /std:c++20 or /std:c++latest

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Create a new UWP project using C++/WinRT
2. Set the langage version to C++ 20 or latest in project settings
3. Make MainPage unsealed in the IDL
4. Create a new XAML page in the project (named BlankPage in the rest of these steps)
5. Remove or rename the MyProperty property from BlankPage.cpp, BlankPage.h and BlankPage.idl to avoid conflicts with the base class
6. Make that page inherit from MainPage from IDL: runtimeclass BlankPage : MainPage (don’t forget import "MainPage.idl";)
7. Add #include "MainPage.h" to BlankPage.h
8. Update BlankPage.xaml to declare a root object of type local:MainPage instead of Page
9. Compile the project
10. Observe the 'to_abi': no matching overloaded function found error

Expected behavior The code should compile correctly and run.

Screenshots

Version Info

NuGet package version: This issue happens whether WinUI 2 is used or not.

Windows app type:

UWP	Win32
Yes	Yes (system XAML islands)

Windows version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context This happens with the Windows SDK version 22000.100, I think it needs to use the v143 toolset as well.

Developer Community issue: https://developercommunity.visualstudio.com/t/Inheriting-from-a-XAML-page-within-the-s/1491603?entry=myfeedback

Sample repro project: BlankApp1.zip (edit 2020-08-02: updated the zip, I somehow managed to upload a zip attempting to use a cppwinrt version that didn’t exist on NuGet)

[ChrisGuzak]

for MS folks this is http://task.ms/35009721

[sylveon]

I had to do a clean build to force the XAML codegen to trigger again, merely upgrading the SDK still used the old codegen - my bad! The issue is resolved now, thanks 😃