#![feature(generators)] use std::cell::Cell; fn main() { fn assert_sync(_: T) {} fn assert_send(_: T) {} assert_sync(|| { //~^ ERROR: generator cannot be shared between threads safely let a = Cell::new(2); yield; }); let a = Cell::new(2); assert_send(|| { //~^ ERROR: E0277 drop(&a); yield; }); }