// check-compile struct DisplayOnly; impl std::fmt::Display for DisplayOnly { fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { unimplemented!() } } fn main() { let x = Some(1); println!("{x:?} {x} {x:?}"); //~^ ERROR: `Option<{integer}>` doesn't implement `std::fmt::Display` println!("{x:?} {x} {x:?}", x = Some(1)); //~^ ERROR: `Option<{integer}>` doesn't implement `std::fmt::Display` let x = DisplayOnly; println!("{x} {x:?} {x}"); //~^ ERROR: `DisplayOnly` doesn't implement `Debug` println!("{x} {x:?} {x}", x = DisplayOnly); //~^ ERROR: `DisplayOnly` doesn't implement `Debug` }