func (n *miniNode) Sym() *types.Sym         { return nil }
func (n *miniNode) Val() constant.Value     { panic(n.no("Val")) }
func (n *miniNode) SetVal(v constant.Value) { panic(n.no("SetVal")) }
func (n *miniNode) NonNil() bool            { return false }

// If pos.IsKnown(), it sets the source position of newly allocated Nodes to pos.
func DeepCopy(pos src.XPos, n Node) Node {
	var edit func(Node) Node
	edit = func(x Node) Node {
		switch x.Op() {
		case ONAME, ONONAME, OLITERAL, ONIL, OTYPE:
			return x
		}
		x = Copy(x)
		if pos.IsKnown() {
			x.SetPos(pos)
		}
		EditChildren(x, edit)
		return x
	}
	return edit(n)
}