third_party/rust/failure_derive/tests/no_derive_display.rs


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extern crate failure;
#[macro_use]
extern crate failure_derive;

use failure::Fail;
use std::fmt::{self, Display};

#[derive(Debug, Fail)]
struct Foo;

impl Display for Foo {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str("An error occurred.")
    }
}

#[test]
fn handwritten_display() {
    assert!(Foo.cause().is_none());
    assert_eq!(&format!("{}", Foo)[..], "An error occurred.");
}