#![warn(print_stdout, use_debug)] use std::fmt::{Debug, Display, Formatter, Result}; #[allow(dead_code)] struct Foo; impl Display for Foo { fn fmt(&self, f: &mut Formatter) -> Result { write!(f, "{:?}", 43.1415) } } impl Debug for Foo { fn fmt(&self, f: &mut Formatter) -> Result { // ok, we can use `Debug` formatting in `Debug` implementations write!(f, "{:?}", 42.718) } } fn main() { println!("Hello"); print!("Hello"); print!("Hello {}", "World"); print!("Hello {:?}", "World"); print!("Hello {:#?}", "#orld"); assert_eq!(42, 1337); vec![1, 2]; }