Bad suggestion when *raw_ptr is used where a reference is expected

[RalfJung]

Code

fn foo(bar: *const [u8]) {
   let baz: &[u8] = unsafe { *bar };
}

Current output

error[E0308]: mismatched types
 --> src/lib.rs:2:30
  |
2 |    let baz: &[u8] = unsafe { *bar };
  |                              ^^^^ expected `&[u8]`, found `[u8]`
  |
help: consider removing deref here
  |
2 -    let baz: &[u8] = unsafe { *bar };
2 +    let baz: &[u8] = unsafe { bar };
  |

Desired output

error[E0308]: mismatched types
 --> src/lib.rs:2:30
  |
2 |    let baz: &[u8] = unsafe { *bar };
  |                              ^^^^ expected `&[u8]`, found `[u8]`
  |
help: consider creating a reference here
  |
2 -    let baz: &[u8] = unsafe { *bar };
2 +    let baz: &[u8] = unsafe { &*bar };
  |

Rationale and extra context

The current suggestion is plain wrong, the result does not build.

Note that one definitely wants the & to go inside the unsafe block to avoid creating a temporary! For this example, the type is non-Copy so a temporary wouldn't even be possible, but in other cases both ways could compiler but they do not behave the same.

Other cases

Rust Version

current nightly

Anything else?

No response

[samueltardieu]

@rustbot claim