type P struct {
	tag string
	_x  [10]uint64
	b   bool
}

type M int

//go:noinline
func (w *M) walkP(p *P) *P {
	np := &P{}
	*np = *p
	np.tag += "new"
	return np
}

func (w *M) walkOp(op *Op) *Op {
	if op == nil {
		return nil
	}

	orig := op
	cloned := false
	clone := func() {
		if !cloned {
			cloned = true
			op = &Op{}
			*op = *orig
		}
	}

	pCloned := false

	// to avoid confusion about what gets returned
	// in the presence of type assertions.
}

func walkStmtList(s []ir.Node) {
	for i := range s {
		s[i] = walkStmt(s[i])
	}
}

// walkFor walks an OFOR node.
func walkFor(n *ir.ForStmt) ir.Node {
	if n.Cond != nil {
		init := ir.TakeInit(n.Cond)
		walkStmtList(init)
		n.Cond = walkExpr(n.Cond, &init)
		n.Cond = ir.InitExpr(init, n.Cond)
	}