S4158 FP: Collection filled using delegates

[markusschaber]

Description

In one of our unit tests, S4158 triggers false positives, the collection clearly is not empty when S4158 claims it is.

Repro steps

This is a cut down snippet from one of our unit tests, requires FluentAssertions (or replace with your favorite assertion syntax).

namespace StaticAnalyzerS4158Bug
{
    using System;
    using System.Collections.Generic;
    using FluentAssertions;

    static class Program
    {
        static void Main(string[] args)
        {
            var collector = new List<int>();

            DoSomething(collector.Add);

            collector[0].Should().Be(42); // Triggers false positives on S4158.
            collector[1].Should().Be(23); // Triggers false positives on S4158.
        }

        private static void DoSomething(Action<int> callback)
        {
            callback(42);
            callback(23);
        }
    }
}

Expected behavior

The rule does not fire when delegates of any methods which can add members have been passed as callback somewhere.

Actual behavior

The rule fires

Known workarounds

Wrap the delegate in a lambda:

            Testee.SubscribeAnalyzerValues(tenant, plcId, i => collector.Add(i));

Related information

• C#/VB.NET Plugins version: SonarLint for Visual Studio 4.33.1.28913
• Visual Studio version: 2019
• MSBuild / dotnet version: .NET Core 3.1
• Operating System: Windows 10

[costin-zaharia-sonarsource]

Hi @markusschaber,

thanks for your feedback. I can confirm the false positive.