impl Display instead of ToString

[andrewbanchich]

What it does

The docs for ToString say:

ToString shouldn’t be implemented directly: Display should be implemented instead

Currently there are no warnings to a direct ToString impl.

Advantage

No response

Drawbacks

No response

Example

impl ToString for Point {
    fn to_string(&self) -> String {
        format!("({}, {})", self.x, self.y)
    }
}

Could be written as:

impl fmt::Display for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "({}, {})", self.x, self.y)
    }
}

[andrewbanchich]

If we're open to the idea of adding this, I'd like to take this on.

[PartiallyUntyped]

Feel free to use @rustbot claim :D

[andrewbanchich]

@rustbot claim

Thanks @partiallytyped !

[asquared31415]

This really seems like something that could be put in rustc directly, since the docs say to not implement it. But it's much easier to get a lint into clippy than rustc and it can always be moved up to rustc.