In Rust's case, this becomes far less practical as soon as the closure's return type does not implement the Copy trait.

Here's an example that does something similar with Vec's: https://play.rust-lang.org/?gist=7a4ed9098a53831195c5189ba9c...

I think the real nastiness happens if you want to have more than one closure over the same variables, when those variables aren't Copy. Because then when you try to `move` them in, the compiler yells at you. At that point you have to resort to putting them in an `Arc<Mutex>` or something like that. But that's par for the course with Rust: the compiler is preventing you from creating multiple mutable references to the same object.