Possibly wrong pattern match in VirtualizingStackPanel.GetControl

[jnyrup]

Describe the bug

In C# the pattern x is not A or B is interpreted as x is (not A) or B and not x is not (A or B).

I was grep'ing my local git repositories for code that matched and stumbled upon

Avalonia/src/Avalonia.Controls/VirtualizingStackPanel.cs

Line 284 in 82e3613

fromControl is null && direction is not NavigationDirection.First or NavigationDirection.Last)

So this code is not checking whether direction is "neither First nor Last".
As Last is covered by not First Roslyn even lowers this to != First.
As such this looks like a bug to me

SharpLab

To Reproduce

I found this by analyzing the code and didn't write any code I don't know and haven't looked into if this potential bug can be hit.

Expected behavior

No response

Avalonia version

master

OS

No response

Additional context

No response

[maxkatz6]

It is wrong, you are correct.
Whole condition should be changed from

if (count == 0 || 
-                fromControl is null && direction is not NavigationDirection.First or NavigationDirection.Last)
+               (fromControl is null && direction != NavigationDirection.First && direction != NavigationDirection.Last)

[timunie]

@jnyrup maybe you can file a PR with the fix? 🙏 thx

[jnyrup]

@jnyrup maybe you can file a PR with the fix? 🙏 thx

Unfortunately I don't have the time to do this.
I'll pass it on to other contributors.