`ptr_arg` false positive on `ToOwned::clone_into()`

[kpreid]

Summary

ptr_arg does not recognize ToOwned::clone_into() as a call that requires &mut String or &mut Vec<T>, and incorrectly suggests changing to &mut str or &mut [T].

Lint Name

ptr_arg

Reproducer

I tried this code:

pub fn t1(mut_string: &mut String, ref_str: &str) {
    ref_str.clone_into(mut_string);
}
pub fn t2(mut_vec: &mut Vec<u8>, ref_slice: &[u8]) {
    ref_slice.clone_into(mut_vec);
}

I saw this happen:

warning: writing `&mut String` instead of `&mut str` involves a new object where a slice will do
 --> src/lib.rs:1:23
  |
1 | pub fn t1(mut_string: &mut String, ref_str: &str) {
  |                       ^^^^^^^^^^^ help: change this to: `&mut str`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_arg
  = note: `#[warn(clippy::ptr_arg)]` on by default

warning: writing `&mut Vec` instead of `&mut [_]` involves a new object where a slice will do
 --> src/lib.rs:4:20
  |
4 | pub fn t2(mut_vec: &mut Vec<u8>, ref_slice: &[u8]) {
  |                    ^^^^^^^^^^^^ help: change this to: `&mut [u8]`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_arg

The suggestions do not compile.

I expected to see this happen: No warnings, since clone_into requires a mutable reference to the owned and resizable type.

Version

Happens with 0.1.70 (2023-04-02 3a8a131) and also latest git 9818ad21678e5e71dcdfd3e3be5a348195e172e0

Additional Labels

@rustbot label +I-suggestion-causes-error