Bad parse error on token sequences `safe unsafe` and `unsafe safe`

[ionicmc-rs]

Code

// #1
unsafe extern {
    safe unsafe fn foo();
    unsafe safe fn bar();
}
// #2
unsafe safe fn baz() {}
safe unsafe fn qux() {}
// #3
unsafe safe extern "C" fn ham() {}
safe unsafe extern "C" fn egg() {}

Current output

# example #1:
`safe` must come before `unsafe`: `safe unsafe`
`unsafe` must come before `safe`: `unsafe safe`
# Example #2
items outside an `unsafe extern {...} block may not be annotated with `safe``
`safe` must come before `unsafe`: `safe unsafe`
`unsafe` must come before `safe`: `unsafe safe`
# example #3 is the same as #2

Desired output

# Example #1
error: `safe` and `unsafe` are incompatible
note: extern functions are unsafe by default
help: if you want to make this function safe, remove `unsafe`
# Example #2
error: items outside an `unsafe extern {...}` block may not be annotated with `safe`
help: remove `safe`
# example #3
error: items outside an `unsafe extern {...}` block may not be annotated with `safe`
note: extern functions are safe by default
help: remove `safe`

Rationale and extra context

look at the errors for #2 and #3:

`safe` must come before `unsafe`: `safe unsafe`
`unsafe` must come before `safe`: `unsafe safe`

this means that it thinks that the order is incorrect

which is likely because they are both included in the check for order

Other cases

// #1
unsafe safe static FOO: i32 = 42;
unsafe safe const BAR: i32 = 42;
unsafe safe trait Baz {}
unsafe trait _X {}
unsafe safe impl _X for i32 {}
// #2 
unsafe extern {
    unsafe safe static QUX: usize = 42;
    // the rest of the examples just copy pasted
}

Output:

# #1 
items outside an `unsafe extern` blocks cannot be `safe`
# shuffle safe and unsafe like usual
# #2 
# same as 1 but without the 'items outside `unsafe extern` ...'

Rust Version

$ rustc --version --verbose
rustc 1.83.0 (90b35a623 2024-11-26)
binary: rustc
commit-hash: 90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf
commit-date: 2024-11-26
host: x86_64-unknown-linux-gnu
release: 1.83.0
LLVM version: 19.1.1

Anything else?

This is a follow up to #133586 and #133631

#133586 has the PR #133618
(all of the above are closed)

[ionicmc-rs]

@rustbot label D-confusing D-terse

[ionicmc-rs]

@rustbot label C-bug A-parser A-edition-2024

[ionicmc-rs]

cc @jieyouxu , he worked on the PR

[fmease]

I haven't looked into the parser like at all for this and I know it was recommended to you to open separate issues here but I find it pretty excessive to open three GH issues for such a niche diagnostic issue:

• Bad parse error on token sequences safe unsafe and unsafe safe #134580
• Bad parse error on token sequences safe unsafe and unsafe safe (before extern blocks) #133586
• Bad parse error on token sequences safe unsafe and unsafe safe (before extern fns) #133630

It may very well be that the underlying code paths and routines differ but in my opinion it's not warranted to track this in three different places (that should only be reserved for more complex issues).

[ionicmc-rs]

Well should i close the old issues? they are irrelevant and incomplete

[fmease]

Pick whichever you like out of the three and close the other two once you've put all the necessary information and reproducers in one place. Thanks a lot for your understanding!