Suggestion for E0740 (union contains a field that needs dropping) doesn't change anything

[PatchMixolydic]

Given the following code (playground):

union U {
    value: Vec<isize>,
}

The current output is:

error[E0740]: unions may not contain fields that need dropping
 --> src/lib.rs:2:5
  |
2 |     value: Vec<isize>,
  |     ^^^^^^^^^^^^^^^^^
  |
note: `std::mem::ManuallyDrop` can be used to wrap the type
 --> src/lib.rs:2:5
  |
2 |     value: Vec<isize>,
  |     ^^^^^^^^^^^^^^^^^

Ideally the output should look like:

error[E0740]: unions may not contain fields that need dropping
 --> src/lib.rs:2:5
  |
2 |     value: Vec<isize>,
  |     ^^^^^^^^^^^^^^^^^
  |
note: `std::mem::ManuallyDrop` can be used to wrap the type
 --> src/lib.rs:2:5
  |
2 |     value: std::mem::ManuallyDrop<Vec<isize>>,
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[PatchMixolydic]

@rustbot modify labels: +D-invalid-suggestion