| //@ run-pass |
| fn with_closure<F, R>(f: F) -> Result<char, R> |
| where F: FnOnce(&char) -> Result<char, R>, |
| { |
| f(&'a') |
| } |
| |
| fn main() { |
| // Test that supplying the `-> Result<char, ()>` manually here |
| // (which is needed to constrain `R`) still allows us to figure |
| // out that the type of `x` is `&'a char` where `'a` is bound in |
| // the closure (if we didn't, we'd get a type-error because |
| // `with_closure` requires a bound region). |
| // |
| // This pattern was found in the wild. |
| let z = with_closure(|x| -> Result<char, ()> { Ok(*x) }); |
| assert_eq!(z.unwrap(), 'a'); |
| |
| // It also works with `_`: |
| let z = with_closure(|x: _| -> Result<char, ()> { Ok(*x) }); |
| assert_eq!(z.unwrap(), 'a'); |
| |
| // It also works with `&_`: |
| let z = with_closure(|x: &_| -> Result<char, ()> { Ok(*x) }); |
| assert_eq!(z.unwrap(), 'a'); |
| } |
