Anonymous Types

[Union]
struct Vector3
{
    public float[3] vals;

    /* Anonymous struct declaration with an anonymous field.
    The below is equivalent to:
    public using struct
    {
        public float mX;
        public float mY;
        public float mZ;
    } _UNUSED_NAME_;
     */
    public struct
    {
        public float x;
        public float y;
        public float z;
    };

    /* Anonymous enum declaration */
    public enum { Left, Center, Right } GetXDirection() => (mX < 0) ? .Left : (mX > 0) ? .Right : .Center;
}

Vector3 vec = .();
vec.mX = 1;
vec.mY = 2;
vec.mZ = 3;

/* Types can anonymously be extended and overriden

*/
var buttonWidget = new ButtonWidget("OK")
{
    bool wasClicked;

    public override void OnClick()
    {
        base.OnClick();
        wasClicked = true;
        CloseDialog();
    }
};