Generic class whose parameter extends a nested class

Question

This C# doesn't compile:

public class IdList<T> where T : IdList<T>.Item {
  List<T> List = new List<T>();

  public T this[int id] {
    get => List[id];
    set { }
  }

  public class Item {
    public int id;
    // Not shown: id used for equality and hash.
  }
}

The complaint from the compiler is:

The type 'IdList' already contains a definition for 'Item'

If I comment out the indexer, it compiles.

How can I get this to compile? Rider doesn't have a fixit.

The unstylish workaround is not to nest the Item class.

IDE is Rider 2018.1.4, Language level 7.2, on macOS.

Answer 1

The issue is that the indexer, when compiled to .NET byte code, becomes a property called "Item". You need to change your type name to something else.