[lmm]

> He didn't say "easy", he said "far from impossible".

That's still overly optimistic when you're talking about something that no-one's ever done.

> You would then address this just as you would any other compiler error - by remediating the failures one by one.

And what do you do in the meantime? Or when you can't see how to fix one of the cases? When a new feature introduces an error, you don't push out the new feature until you can fix the error, possibly never. When a compiler upgrade introduces an error all over your codebase (that you can't fix with something like a one-liner regex), you turn it off (in the best case you turn it into a warning that you then maybe gradually fix), and if you can't turn it off you don't do the compiler upgrade.