Bug: Trying to enumerate the result of DisplayArea.FindAll() throws an InvalidCastException

[benstevens48]

Description

With AOT on, call Microsoft.UI.Windowing.DisplayArea.FindAll().ToList() or anything else that tries to call GetEnumerator on the result of DisplayArea.FindAll() and it fails with an InvalidCastException. The stack trace is

[System.InvalidCastException user-unhandled]	
>	WinRT.Runtime.dll!WinRT.IObjectReference.As<WinRT.Interop.IUnknownVftbl>(System.Guid iid) Line 139	C#
 	WinRT.Runtime.dll!System.Collections.Generic.IReadOnlyListImpl<Microsoft.UI.Windowing.DisplayArea>.Make_IEnumerableObjRef() Line 47	C#
 	WinRT.Runtime.dll!System.Collections.Generic.IReadOnlyListImpl<Microsoft.UI.Windowing.DisplayArea>.iEnumerableObjRef.get() Line 25	C#
 	WinRT.Runtime.dll!System.Collections.Generic.IReadOnlyListImpl<Microsoft.UI.Windowing.DisplayArea>.GetEnumerator() Line 75	C#

Note that I wouldn't say this was a duplicate of #747 as previously suggested in this issue microsoft/microsoft-ui-xaml#6454 since no covariance is involved here. Also, this is not the System.ArgumentOutOfRangeException mentioned in that issue. The workaround of using an integer indexer as in microsoft/microsoft-ui-xaml#6454 (comment) works.

Steps To Reproduce

See description

Expected Behavior

No exception

Version Info

CsWinRT 2.2, WindowsAppSdk.WinUI 1.8.260204000 (+ transitive dependencies), Windows 25H2.

Additional Context

No response

[manodasanW]

This looks like an issue with the underlying API as the QueryInterface call for IEnumerable<DisplayArea> is the one failing here. I confirmed in a C++/WinRT app too that the call to First from IVectorView also fails there. I will look at opening a bug on the team that owns this API.

Internal tracking: http://task.ms/61702195

[benstevens48]

Ok, thanks! I probably should have checked the underlying API, but I assumed that would have been tested before shipping it! Feel free to close this issue if it is being tracked elsewhere.