您在Rust中无法做的事情：关闭复制

我爱Rust，希望它变得更好。 开发团队知道所有提出的问题。 我只是想引起大家的讨论和热情，以使一种好的语言变得更好。

fn main() {
   // Many closures can now be passed by-value to multiple functions:
   fn call(f: F) { f() }
   let hello = || println!("Hello, world!");
   call(hello);
   call(hello);

   // Many `Iterator` combinators are now `Copy`/`Clone`:
   let x = (1..100).map(|x| x * 5);
   let y = x.map(|x| x - 3); // moves `x` by `Copy`ing
   let _ = x.chain(y); // moves `x` again
   let _ = x.cycle(); // `.cycle()` is only possible when `Self: Clone`

   // Closures which reference data mutably are not `Copy`/`Clone`:
   let mut x = 0;
   let incr_x = || x += 1;
   call(incr_x);
   call(incr_x); // ERROR: `incr_x` moved in the call above.

   // `move` closures implement `Clone`/`Copy` if the values they capture
   // implement `Clone`/`Copy`:
   let mut x = 0;
   let print_incr = move || { println!("{}", x); x += 1; };

   fn call_three_times(mut f: F) {
      for i in 0..3 {
         f();
      }
   }
   call_three_times(print_incr); // prints "0", "1", "2"
   call_three_times(print_incr); // prints "0", "1", "2"
}

结果（编译时错误）：

 error[E0277]: the trait bound `[[email protected]:9:24: 9:33]: std::clone::Clone` is not satisfied
   |
12 |   let _ = x.cycle(); // `.cycle()` is only possible when `Self: Clone`
   |             ^^^^^ the trait `std::clone::Clone` is not implemented for `[[email protected]:9:24: 9:33]`
   |
   = note : required because of the requirements on the impl of `std::clone::Clone` for `std::iter::Map, [[email protected]:9:24: 9:33]>`

 error: aborting due to previous error(s) 

公平地说，此功能已部分实现。 要实现Copy，编译器需要注意生存期和可变性，因此这不是一个简单的功能。 到目前为止，已经涵盖了许多常见情况，但是如RFC（2132）示例所示，还有很长的路要走。 目前，这是对关闭的另一个警告。

From: https://hackernoon.com/things-you-cant-do-in-rust-copy-closures-79d2c0586da