The winit event loop API has weird consequences with borrow checker

main.rs

use winit;

struct Game {
  window: winit::Window,
  ev: winit::EventLoop
}

impl Game {
  fn new() -> Game {
    let ev = winit::EventsLoop::new();
    let window = winit::Window::new()
        .build(&ev)
        .unwrap();
    Game {
      ev,
      window
    }
  }
  
  fn run<F: Fn()>(&mut self, f: F) {
    self.ev.run_forever(|event| {
      match event {
        _ => {} 
      }
      f();
      winit::ControlFlow::Continue
    });
  }
}

fn main() {
  let mut game = Game::new();
  
  // CAN'T USE MUT GAME HERE BECAUSE IT'S IMMUTABLY BORROWED IN THE ANON FN
  // v
  game.run(|| {
    // BORROWS GAME IMMUTABLY
    // use game.window.width or whatever
  });
  
  // It's really weird because you can't just create the event loop
  // object when you want to either, it has to be created _before_ you
  // can create a window.
  
  // lambdas, mutability and the borrow checker are spooky to untangle.
  
  // p.s. trying to fix somebody else's code, this wouldn't be
  // my first choice of design. (They changed the winit api, so updating some
  // example code)
}