The chapter on macros http://doc.rust-lang.org/book/macros.html#hygiene mentions a "lifetime guide" when using loop labels. As far as I can tell, that guide does not exist anymore (or it has been renamed when becoming a chapter). If that's correct, then loop labels are not mentioned anywhere else in the book, so this subsection is rather hard to follow. If the lifetime guide still exists somewhere, but has been renamed, then the text should be updated (preferably adding a link).
The chapter on macros http://doc.rust-lang.org/book/macros.html#hygiene mentions a "lifetime guide" when using loop labels. As far as I can tell, that guide does not exist anymore (or it has been renamed when becoming a chapter). If that's correct, then loop labels are not mentioned anywhere else in the book, so this subsection is rather hard to follow. If the lifetime guide still exists somewhere, but has been renamed, then the text should be updated (preferably adding a link).