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use std::cell::Cell;
use std::rc::Rc;
// Fast path, main can see the concrete type returned.
fn before() -> impl Fn(i32) {
let p = Rc::new(Cell::new(0));
move |x| p.set(x)
}
fn send<T: Send>(_: T) {}
fn main() {
send(before());
//~^ ERROR `std::rc::Rc<std::cell::Cell<i32>>` cannot be sent between threads safely
send(after());
//~^ ERROR `std::rc::Rc<std::cell::Cell<i32>>` cannot be sent between threads safely
}
// Deferred path, main has to wait until typeck finishes,
// to check if the return type of after is Send.
fn after() -> impl Fn(i32) {
let p = Rc::new(Cell::new(0));
move |x| p.set(x)
}
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