needless_borrow seems to be too eager in beta 1.66

Summary

Since beta 1.66, the needless_borrow lint is warning that "the borrowed expression implements the required traits" when passing a parameter by reference.

This can have an issue because let's say in the example below, the function needs_to_reuse_string will cause a version of very_large_function that takes _s: &String to be instantiated. Since does_not_need_to_reuse_string calls very_large_function with the same parameter type, no extra version is instantiated. If the clippy suggestion is obeyed, does_not_need_to_reuse_string will cause an extra instantiation of very_large_function which takes _s: String.

In summary, I don't get why the needless_borrow lint was broadened to warn about pass-by-reference when both pass-by-value and pass-by-reference are accepted. And even if it would be desirable to some, I don't agree with lumping that behaviour with needless_borrow which I find useful to catch stuff like &already_a_reference.

Lint Name

needless_borrow

Reproducer

I tried this code:

fn very_large_function<S: AsRef<[u8]>>(_s: S) {
    unimplemented!();
}

pub fn does_not_need_to_reuse_string() {
    let s = String::from("hello");
    very_large_function(&s);
}

pub fn needs_to_reuse_string() {
    let s = String::from("hello");
    very_large_function(&s);
    drop(s);
}

I saw this happen:

warning: the borrowed expression implements the required traits
 --> src/lib.rs:7:25
  |
7 |     very_large_function(&s);
  |                         ^^ help: change this to: `s`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow
  = note: `#[warn(clippy::needless_borrow)]` on by default

I expected to see no warnings.

Version

rustc 1.66.0-beta.1 (e080cc5a6 2022-11-01)
binary: rustc
commit-hash: e080cc5a659fb760c0bc561b722a790dad35b5e1
commit-date: 2022-11-01
host: x86_64-unknown-linux-gnu
release: 1.66.0-beta.1
LLVM version: 15.0.2

Additional Labels

No response

Reproduce the needless_borrow warning from the example in src/lib.rs using the reported beta version, then inspect the lint's implementation and tests. Done means the pass-by-reference call in does_not_need_to_reuse_string no longer receives this warning while genuinely redundant borrows, such as borrowing an already borrowed value, remain covered.