in 2021.3/CS10/PatternMatching/SimplifyPatternMatchingDottedAccess.cs [5:22]
public void Demo()
{
var user1 = new User();
if (user1 is { Tags.Count: 0 }) // CA "Split into nested patterns" over dot
{
// ...
}
var user = new User();
if (user is { Tags: { Count: 0 } })
{
// ...
}
}