src/test/ui/async-await/async-fn-nonsend.rs

   1 // edition:2018
   2 // compile-flags: --crate-type lib
   3
   4 use std::{cell::RefCell, fmt::Debug, rc::Rc};
   5
   6 fn non_sync() -> impl Debug {
   7     RefCell::new(())
   8 }
   9
  10 fn non_send() -> impl Debug {
  11     Rc::new(())
  12 }
  13
  14 fn take_ref<T>(_: &T) {}
  15
  16 async fn fut() {}
  17
  18 async fn fut_arg<T>(_: T) {}
  19
  20 async fn local_dropped_before_await() {
  21     // FIXME: it'd be nice for this to be allowed in a `Send` `async fn`
  22     let x = non_send();
  23     drop(x);
  24     fut().await;
  25 }
  26
  27 async fn non_send_temporary_in_match() {
  28     // We could theoretically make this work as well (produce a `Send` future)
  29     // for scrutinees / temporaries that can or will
  30     // be dropped prior to the match body
  31     // (e.g. `Copy` types).
  32     match Some(non_send()) {
  33         Some(_) => fut().await,
  34         None => {}
  35     }
  36 }
  37
  38 async fn non_sync_with_method_call() {
  39     // FIXME: it'd be nice for this to work.
  40     let f: &mut std::fmt::Formatter = panic!();
  41     if non_sync().fmt(f).unwrap() == () {
  42         fut().await;
  43     }
  44 }
  45
  46 fn assert_send(_: impl Send) {}
  47
  48 pub fn pass_assert() {
  49     assert_send(local_dropped_before_await());
  50     //~^ ERROR future cannot be sent between threads safely
  51     assert_send(non_send_temporary_in_match());
  52     //~^ ERROR future cannot be sent between threads safely
  53     assert_send(non_sync_with_method_call());
  54     //~^ ERROR future cannot be sent between threads safely
  55 }