unsafe const fn should recover-parse as const unsafe fn

[saethlin]

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=125d16cb6ffba02dc50df65194611ec5

Code

struct Thing {}

impl Thing {
    unsafe const fn from_u32(val: u32) -> Self {
        Self {}
    }
    
    fn oof(self) -> u32 {
        0
    }
}

fn main() {
    Thing {}.oof();
}

Current output

error: expected one of `extern` or `fn`, found keyword `const`
  --> src/main.rs:4:12
   |
3  | impl Thing {
   |            - while parsing this item list starting here
4  |     unsafe const fn from_u32(val: u32) -> Self {
   |     -------^^^^^
   |     |      |
   |     |      expected one of `extern` or `fn`
   |     help: `const` must come before `unsafe`: `const unsafe`
...
11 | }
   | - the item list ends here
   |
   = note: keyword order for functions declaration is `pub`, `default`, `const`, `async`, `unsafe`, `extern`

error[[E0599]](https://doc.rust-lang.org/stable/error_codes/E0599.html): no method named `oof` found for struct `Thing` in the current scope
  --> src/main.rs:14:14
   |
1  | struct Thing {}
   | ------------ method `oof` not found for this struct
...
14 |     Thing {}.oof();
   |              ^^^ method not found in `Thing`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground` (bin "playground") due to 2 previous errors

Desired output

The compiler should understand that I just got the keyword order wrong, and recover-parse appropriately, instead of losing track of all methods in the impl.

Rationale and extra context

No response

Other cases

No response

Anything else?

No response