> come to think of it, you don't often write "&&T", but it is commonly used. If you `println!("{}", x)` where "x" is a reference, the "println!" macro also takes a reference and you get a "&&" type.

Yup, i see them all the time in iterators too. Eg `foos.iter().filter(|t| ..` `t` is `&&Foo` in that example, iirc. Not that you usually see it though, due to closures obscuring types.