When does a closure implement the Fn, FnMut, and FnOnce traits in Rust?

Hello, colleagues! I started learning Rust and can't figure out closures. The documentation says that every closure automatically implements one or more traits: `Fn`, `FnMut`, and `FnOnce`. But I don't understand what this depends on. Let's say I have simple code: ```rust let mut x = 5; let add_to_x = |y| x += y; // closure that mutates x let print_x = || println!("{}", x); // closure that reads x ``` Why can `add_to_x` not be used as `Fn`, but `print_x` can? And when does a closure become `FnOnce`? I tried passing closures to functions with different trait bounds, and the compiler complains that the trait is not implemented. Can you explain in simple terms how the Rust compiler decides which trait to implement for a closure? And how does this affect