[nh1996]

This would require the SinglyLinkedList to be generic and would require that the data struct use "node" as the field name. Also, as some comments have pointed out, this type of linked list can be useful when a data struct needs to be in multiple lists, in which case there is no single "node" field.

  const some_data = struct {
    // Some data fields
    // ...
    bar_node: SinglyLinkedList.Node,
    baz_node: SinglyLinkedList.Node,
  };

[throwawaymaths]

sure, just make T == void fall back to the existing implementation.