src/test/ui/impl-trait/auto-trait-leak2.rs

   1 use std::cell::Cell;
   2 use std::rc::Rc;
   3
   4 // Fast path, main can see the concrete type returned.
   5 fn before() -> impl Fn(i32) {
   6     let p = Rc::new(Cell::new(0));
   7     move |x| p.set(x)
   8 }
   9
  10 fn send<T: Send>(_: T) {}
  11
  12 fn main() {
  13     send(before());
  14     //~^ ERROR `Rc<Cell<i32>>` cannot be sent between threads safely
  15
  16     send(after());
  17     //~^ ERROR `Rc<Cell<i32>>` cannot be sent between threads safely
  18 }
  19
  20 // Deferred path, main has to wait until typeck finishes,
  21 // to check if the return type of after is Send.
  22 fn after() -> impl Fn(i32) {
  23     let p = Rc::new(Cell::new(0));
  24     move |x| p.set(x)
  25 }