This is what the `AsRef` trait is great for impl AsRef<str> for MyCoolString { fn as_ref(&self) -> &str { ... } } To be to

This is what the `AsRef` trait is great for impl AsRef<str> for MyCoolString { fn as_ref(&self) -> &str { ... } } To be totally defensive, other library authors can write their APIs like fn my_cool_function(s: impl AsRef<str>) { let s: &str = s.as_ref(); } and now `s` is treated like any other &str. But even if library authors don't program defensively and use `s: &str` in the argument type, callers can always do this: my_cool_function(my_cool_string.as_ref());