if len(p) > nr.n {
		p = p[:nr.n]
	}
	n := copy(p, r.source)
	r.source = r.source[n:]
	return n, nr.err
}

// tests that we don't ignore errors from our underlying reader
func TestDecoderIssue3577(t *testing.T) {
	next := make(chan nextRead, 10)
	wantErr := errors.New("my error")
	next <- nextRead{5, nil}
	next <- nextRead{10, wantErr}
	next <- nextRead{0, wantErr}