if err != nil {
		t.Fatalf("tr.Next: %v", err)
	}
	if !reflect.DeepEqual(rHdr, hdr) {
		t.Errorf("Header mismatch.\n got %+v\nwant %+v", rHdr, hdr)
	}
	rData, err := io.ReadAll(tr)
	if err != nil {
		t.Fatalf("Read: %v", err)
	}
	if !bytes.Equal(rData, data) {
		t.Errorf("Data mismatch.\n got %q\nwant %q", rData, data)
	}
}

type headerRoundTripTest struct {
	h  *Header
	fm fs.FileMode
}

// ReadWriter stores pointers to a [Reader] and a [Writer].
// It implements [io.ReadWriter].
type ReadWriter struct {
	*Reader
	*Writer
}

// NewReadWriter allocates a new [ReadWriter] that dispatches to r and w.
func NewReadWriter(r *Reader, w *Writer) *ReadWriter {
	return &ReadWriter{r, w}

	VMOV	V8.D[0], V12.H[1]                                // ERROR "operand mismatch"
	VMOV	V8.D[0], V12.B[1]                                // ERROR "operand mismatch"
	VMOV	V8.S[0], V12.H[1]                                // ERROR "operand mismatch"
	VMOV	V8.S[0], V12.B[1]                                // ERROR "operand mismatch"