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 = &Some(3); let y: Option<&usize> = x; //~ ERROR mismatched types [E0308] let x: &Result = &Ok(3); let y: Result<&usize, &usize> = x; //~^ ERROR mismatched types [E0308] // note: do not suggest because of `E: usize` let x: &Result = &Ok(3); let y: Result<&usize, usize> = x; //~ ERROR mismatched types [E0308] }