[scoutt]

I think the snippet is part of the example code for Mutex. Here: https://doc.rust-lang.org/std/sync/struct.Mutex.html

After "It is sometimes necessary to manually drop the mutex..."

[steveklabnik]

Ah ha! I should have recognized it, given that I'm pretty sure I wrote that, haha.

Incidentally, this is one reason why I've been advocating for a return of scoped threads to libstd; I can't change this example to be the "good" one, because we don't refer to external packages and we don't have scoped threads built-in.