assert_eq!() Should be able to compare &str with String

[mcandre]

Hey, could the assert_eq!() macro become more helpful, in particular allowing comparisons between &str's and String's?

[qnighy]

Just one & allows such comparison, I suppose.

fn main() {
    let mut s = String::from("foo");
    assert_eq!(&s, "foo");
    s.push_str("bar");
    assert_eq!(&s, "foobar");
    s.push_str("baz");
    assert_ne!(&s, "foobarbar");
}

[leoschwarz]

Would it be actually good if assert_eq! would test values as equal which == wouldn't?

Like I can see it making writing tests more easy but at the same time it might be potentially confusing.

[dtolnay]

The standard library provides all of the following impls so I believe this is supported now.

lhs \ rhs	str	&str	String	Cow<str>
str	✔️		✔️	✔️
&str		✔️	✔️	✔️
String	✔️	✔️	✔️	✔️
Cow<str>	✔️	✔️	✔️	✔️

fn main() {
    let s = String::new();
    assert_eq!(s, "");
    assert_eq!("", s);
}