Why is this an issue?
Passing a collection as an argument to the collection’s own method is either an error - some other argument was intended - or simply nonsensical
code.
Further, because some methods require that the argument remain unmodified during the execution, passing a collection to itself can result in an
unexpected behavior.
Noncompliant code example
var list = new List<int>();
list.AddRange(list); // Noncompliant
list.Concat(list); // Noncompliant
list.Union(list); // Noncompliant; always returns list
list.Except(list); // Noncompliant; always empty
list.Intersect(list); // Noncompliant; always list
list.SequenceEqual(list); // Noncompliant; always true
var set = new HashSet<int>();
set.UnionWith(set); // Noncompliant; no changes
set.ExceptWith(set); // Noncompliant; always empty
set.IntersectWith(set); // Noncompliant; no changes
set.IsProperSubsetOf(set); // Noncompliant; always false
set.IsProperSupersetOf(set); // Noncompliant; always false
set.IsSubsetOf(set); // Noncompliant; always true
set.IsSupersetOf(set); // Noncompliant; always true
set.Overlaps(set); // Noncompliant; always true
set.SetEquals(set); // Noncompliant; always true
set.SymmetricExceptWith(set); // Noncompliant; always empty
