C# S2583 - False Positive on null check if another type check is earlier in the same function call

Clean Code Report False-positive / False-negative...
1

The analyzer reports S2583 - condition always evaluates to false in this example:

private static void TestIsNull2(int a, int b, int c)
{
    Console.WriteLine($"{a}, {b}, {c}");
}

public static void TestIsNull1(object value)
    => TestIsNull2(
        value is null ? 1 : 2,
        value is bool b ? 3 : 4,
        value is null ? 5 : 6);

image
image1084×361 17.2 KB

The FP is only on the last line (although the first like has the same condition) and it disappears if the redundant bool variable b declaration is removed and only the type is checked in that line!?

The analyzer version is 8.4.0.15306

2

Zdravim Miroslave,

Thank you for reporting this interesting case.

We’ve confirmed this as FP and created this issue to track it.