C++ lambdas need that feature because they don't have lifetimes or a borrow checker. Rust closures don't need that feature because rust has a borrow checker that ensures you aren't referencing something you shouldn't be.
You can explicitly decide what to copy inside a Rust closure as well, you just use a `move` closure and create references for anything you need referenced outside the closure instead.
Parent is saying that you can declare your closure 'move' and move references rather than values, therefore getting the mixed behavior you described. You don't have to move all values.
If you want to copy in such cases in Rust, you need to copy to dummy variables that are then moved into the closure, a common pattern in Gtk-rs that even deserves a macro to simplify the boilerplate.
You can explicitly decide what to copy inside a Rust closure as well, you just use a `move` closure and create references for anything you need referenced outside the closure instead.