Unnecessary call to to_string when the underlying type implements AsRef<str> #7933
Description
What it does
Checks for expressions of the form &X.to_string(), used in a position requiring a &str, where X implements AsRef<str>.
In such a case, the call to to_string is unnecessary.
Similar to to_string/AsRef<str>, there's also to_path_buf/AsRef<Path> and to_vec/AsRef<[T]>.
There are probably others.
I am happy to tackle this if we can agree on the check, and whether it is useful.
Categories (optional)
- Kind: perf
Drawbacks
Potential "false positives" if X's AsRef<str> and to_string implementations produce different strings. But I would expect such cases to be rare.
Example
use std::{fmt::Write, io::Write as OtherWrite};
fn main() {
let mut s = String::new();
let dir = std::env::current_dir().unwrap();
s.write_str(&dir.to_string_lossy().to_string()).unwrap();
// ^^^^^^^^^^^^ unnecessary
s.write_str(" is the current directory.\n").unwrap();
std::io::stdout().write(s.as_bytes()).unwrap();
}