unnecessary_sort_by suggests broken code

[matthiaskrgr]

I tried this code:

#[derive(Ord, PartialOrd, Eq, PartialEq)]
struct A<'a> {
    name: &'a str,
}

impl A<'_> {
    fn name(&self) -> &str {
        &self.name
    }
}

fn main() {
    let a = A { name: "" };
    let b = A { name: "" };
    let mut v = vec![a, b];
    v.sort_by(|a, b| a.name().cmp(b.name()))
}

Clippy suggested

warning: use Vec::sort_by_key here instead
  --> src/main.rs:16:5
   |
16 |     v.sort_by(|a, b| a.name().cmp(b.name()))
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `v.sort_by_key(|&a| a.name())`
   |
   = note: `#[warn(clippy::unnecessary_sort_by)]` on by default
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_sort_by

warning: 1 warning emitted

but the suggestion does not compile:

error[E0507]: cannot move out of a shared reference
  --> src/main.rs:16:20
   |
16 |     v.sort_by_key(|&a| a.name())
   |                    ^-
   |                    ||
   |                    |data moved here
   |                    |move occurs because `a` has type `A<'_>`, which does not implement the `Copy` trait
   |                    help: consider removing the `&`: `a`

error[E0515]: cannot return value referencing local variable `a`
  --> src/main.rs:16:24
   |
16 |     v.sort_by_key(|&a| a.name())
   |                        -^^^^^^^
   |                        |
   |                        returns a value referencing data owned by the current function
   |                        `a` is borrowed here

error: aborting due to 2 previous errors

Meta

• cargo clippy -V: e.g. clippy 0.0.212 (346aec9 2020-07-11)
• rustc -Vv:

  rustc 1.46.0-nightly (346aec9b0 2020-07-11)
  

binary: rustc
commit-hash: 346aec9
commit-date: 2020-07-11
host: x86_64-unknown-linux-gnu
release: 1.46.0-nightly
LLVM version: 10.0

[matthiaskrgr]

Looks like #5754 :/