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// 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');
}
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