rust/src/test/ui/suggestions/as-ref.rs

struct Foo;

fn takes_ref(_: &Foo) {}

fn main() {
    let ref opt = Some(Foo);
    opt.map(|arg| takes_ref(arg)); //~ ERROR mismatched types [E0308]
    opt.and_then(|arg| Some(takes_ref(arg))); //~ ERROR mismatched types [E0308]
    let ref opt: Result<_, ()> = Ok(Foo);
    opt.map(|arg| takes_ref(arg)); //~ ERROR mismatched types [E0308]
    opt.and_then(|arg| Ok(takes_ref(arg))); //~ ERROR mismatched types [E0308]
    let x: &Option<usize> = &Some(3);
    let y: Option<&usize> = x; //~ ERROR mismatched types [E0308]
    let x: &Result<usize, usize> = &Ok(3);
    let y: Result<&usize, &usize> = x;
    //~^ ERROR mismatched types [E0308]
    // note: do not suggest because of `E: usize`
    let x: &Result<usize, usize> = &Ok(3);
    let y: Result<&usize, usize> = x; //~ ERROR mismatched types [E0308]
}