S4158 FP: Collection filled in a for loop reported to be empty

[Keke71]

Description

Sonar Analyzer incorrectly reports S4158 for the code below. My original code is actually more complex. However, this simplified example also reports S4158.

Repro steps

public void FalsePositive()
{
    var data = new[] { 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0 };
    var rising = new List<List<int>>();
    List<int> currentBin = null;
    for (var i = 0; i < data.Length; i++)
    {
        if (data[i] == 0)
        {
            if (currentBin != null)
            {
                rising.Add(currentBin);
                currentBin = null;
            }
    
            continue;
        }
    
        currentBin ??= new List<int>();
        currentBin.Add(i);
    }
    
    for (var i = 0; i < rising.Count; i++)
    {
        // SonarAnalyzer reports S4158 here:
        Console.WriteLine($"{rising[i].Count}");
    }
}

Expected behavior

As the collection is not empty, no issue should be reported.

Actual behavior

S4158 is reported.

Known workarounds

Using a foreach loop in the lower part, does not report the issue. However, in my original code this is not possible, as I actually have two collections that I have to access with indices.

Related information

Environment:
- Visual Studio Enterprise 17.3.0
- SonarAnalyzer.CSharp 8.46.0.54807
- .NET Framework 4.8
- Windows 10 x64

[pavel-mikula-sonarsource]

Hi @Keke71,

Thank you for reporting this, as discussed on the other thread, I confirm it as a False Positive.

For archeology: MMF-2402 (nonpublic link) will migrate this rule to the new engine