const _und = 0

type fullTag interface {
	IsRoot() bool
	Parent() language.Tag
}

// Make a compact Tag from a fully specified internal language Tag.
func Make(t language.Tag) (tag Tag) {
	if region := t.TypeForKey("rg"); len(region) == 6 && region[2:] == "zzzz" {
		if r, err := language.ParseRegion(region[:2]); err == nil {
			tFull := t
			t, _ = t.SetTypeForKey("rg", "")
			// TODO: should we not consider "va" for the language tag?