Reborrowing (`&mut *x`) is not suggested as a potential solution for `&mut T` being moved

Code

fn do_something<T>(_a: &mut T, _b: &mut T) {}

fn foo<T: Default>(r: &mut T) {    
    let mut a = T::default();
    let b = r;
    do_something(&mut a, b);
    *r = a;
}

Current output

error[E0382]: use of moved value: `r`
 --> src/lib.rs:7:5
  |
3 | fn foo<T: Default>(r: &mut T) {    
  |                    - move occurs because `r` has type `&mut T`, which does not implement the `Copy` trait
4 |     let mut a = T::default();
5 |     let b = r;
  |             - value moved here
6 |     do_something(&mut a, b);
7 |     *r = a;
  |     ^^ value used here after move

For more information about this error, try `rustc --explain E0382`.
error: could not compile `moved` (lib) due to 1 previous error

Desired output

help: try reborrowing: `let b = &mut *r;`
                                ++++++

Rationale and extra context

A rather trivial fix, but not very easy to recall it even exists, because in most places compiler does this for you automatically (iinm). For example, I think Rust always inserts &mut * when a &mut T is passed as an argument to a call.

Other cases

Similar to #81059 & #82453, but those also involve pattern matching.

Similar to #129694, but example there is more complex, with some type inference involved.

Similar to #81772, but that issue seems to be about expecting the compiler to automatically insert &mut * and not about the diagnostic quality. The diagnostics there actually does suggest to add a reborrow (as of nightly 2025-01-24).

Same thing with #85161: it is not about diagnostics but about compiler not reborrowing automatically. The diagnostic there does suggest reborrowing too.

More or less a duplicate of #74706? Feel free to close either one if you think these are indeed duplicates.

Rust Version

$ rustc --version --verbose
rustc 1.86.0-nightly (1e9b0177d 2025-01-24)
binary: rustc
commit-hash: 1e9b0177da38e3f421a3b9b1942f1777d166e06a
commit-date: 2025-01-24
host: x86_64-unknown-linux-gnu
release: 1.86.0-nightly
LLVM version: 19.1.7

Anything else?

If not for the Boats's post on pinned places, I don't think I would even realize I can do &mut * to fix the error I got, despite several years of actively using Rust under my belt.

Reproduce the example in src/lib.rs and run rustc --explain E0382 to understand the current diagnostic. Trace the diagnostic behavior for the moved &mut T and make the completed output suggest let b = &mut *r; as shown in the desired output.