I agree that that's a problem! It's particularly bad right now, because the docs have been tracking HEAD, but the last time a release came out was March, and that's a long, long time ago in Rust time. But! First, we're coming out with a release in the next couple of days, so the released version will be caught up with the docs again, and second, from now on the docs will be versioned along with the compiler, so this won't happen. It's exciting that Rust now has enough users that this kind of thing has started to matter.