Clippy invalid suggestion for format!("{}", &s)

[ghost]

I tried to clippy --fix this code

#![allow(dead_code)]

enum A {
    B(String),
    C,
}

fn main() {
    let a = A::C;
    let s: String = match a {
       A::B(s) => format!("{}", &s),
       A::C => format!("{}", "hello"),
    };
    println!("{}", s);
}

This fixes to:

match a {
    A(s) => &s.to_string(),
    B(_) => "hello".to_string(),
}

But now the different branches have different types. This highlights that the suggested fix even on stable is not correct:

warning: useless use of `format!`
  --> src/main.rs:11:19
   |
11 |        A::B(s) => format!("{}", &s),
   |                   ^^^^^^^^^^^^^^^^^ help: consider using `.to_string()`: `&s.to_string()`
   |
   = note: `#[warn(clippy::useless_format)]` on by default
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_format

It should suggest

help: consider using `.to_string()`: `(&s).to_string()`

Meta

• cargo clippy -V: clippy 0.1.51 (2fd73fab 2021-03-23)
• cargo +nightly-x86_64-apple-darwin clippy -V: clippy 0.1.52 (07e0e2e 2021-03-24)
• rustc -Vv:

rustc 1.51.0 (2fd73fabe 2021-03-23)
binary: rustc
commit-hash: 2fd73fabe469357a12c2c974c140f67e7cdd76d0
commit-date: 2021-03-23
host: x86_64-apple-darwin
release: 1.51.0
LLVM version: 11.0.1

[basavesh]

#7092 Fixes this.

+error: useless use of format!

• --> $DIR/format.rs:82:19
• |
  +LL | A::B(s) => format!("{}", &s),
• | ^^^^^^^^^^^^^^^^^ help: consider using .to_string(): (&s).to_string()

+error: useless use of format!

• --> $DIR/format.rs:83:16
• |
  +LL | A::C => format!("{}", "hello"),
• | ^^^^^^^^^^^^^^^^^^^^^^ help: consider using .to_string(): "hello".to_string()

+error: aborting due to 16 previous errors

[giraffate]

#7092 fixed this, so I'm closing this.