S4201 — Null checks should not be combined with "TypeOf Is" operator checks

Why is this an issue?

There’s no need to null test in conjunction with an TypeOf ... Is test. Nothing is not an instance of anything, so a null check is redundant.

Noncompliant code example

If (x IsNot Nothing And TypeOf x Is MyClass)
    ' ...
End If

If (x Is Nothing Or TypeOf x IsNot MyClass)
    ' ...
End If

Compliant solution

If (TypeOf x Is MyClass)
    ' ...
End If

If (TypeOf x IsNot MyClass)
    ' ...
End If