Fix S2589 FP with nullable value types

[csaba-sagi-sonarsource]

Description

S2589 raises a false positive when used with nullable value types.

Repro steps

protected void Test(decimal? value1, decimal? value2)
{
    if (value1 == null || value2 == null || value1 != value2)
    {
        Console.WriteLine("test");
    }
}

Expected behavior

No issue is raised.

Actual behavior

An issue is riased.

Related information

• C#/VB.NET Plugins version: 8.33.0.40503

[shuebner]

S2589 will trigger on null, too, e. g.

int? foo = (int?)6 ?? null;

[mary-georgiou-sonarsource]

Fixed by https://github.com/SonarSource/sonar-dotnet/pull/7750