SE: Learn more constraints when learning from FirstOrDefault, LastOrDefault and SingleOrDefault

[mary-georgiou-sonarsource]

In the following case , we should also learn a CollectionConstraint.

void Method(List<string> list)
{
    var first = list.FirstOrDefault();
    // branch into:
    // first: Null, list: Empty
    // first: NotNull, list:NotEmpty
}

void Method(List<string> list)
{
    var first = list.FirstOrDefault(x => x.Length > 5);
    // branch into:
    // first: Null
    // first: NotNull, list: NotEmpty
}

The method that needs to be modified is Invocation.ProcessElementOrDefaultMethods here.