Fix S2259 FP: SE engine doesn't take into account element existence collection methods

[sebastien-marichal]

From this community post.

This might be fixed as part of #7457:

Learn from well-known (extension-) methods like list.Any()

void Method(Exception[] array)
{
    if (array.Any())
    {
        Exception exception = array.FirstOrDefault();
        Console.WriteLine(exception.Message); // Noncompliant - FP if Any is true, FirstOrDefault will never return null
    }
}

[Tim-Pohlmann]

This requires the mentioned step from #7457 + extra logic for FirstOrDefault. Should be straight-forward after #7866

[mary-georgiou-sonarsource]

@Tim-Pohlmann @sebastien-marichal For the record, this example is a true positive, as FirstOrDefault can return null even if the collection is not empty for reference types.

[Tim-Pohlmann]

@mary-georgiou-sonarsource That's a Good catch. The engine needs to learn unknown and not NotNull here. This means it is still an FP because S2259 does not raise on unknown.