People have definitely died just from the two separately, and especially combined so I have no idea why anyone would say it's impossible because it definitely can kill you. The thing is, you're way more likely to live, so it is not at all reliable and more likely to cause damage and a horrible hangover then death. Back in my partying days in my early 20's (in my 30's now), I've combined large amounts of opiates, alcohol, benzos and a couple of times even MDMA (all being injected except the alcohol) and I wasn't even trying to kill myself, I was stupid but I'm still alive.