Implement check_attribute to forbid #[allow_internal_unsafe]

[JohnTitor]

Fixes #56768.

r? @oli-obk

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[oli-obk]

Can you add a test if no preexisting test is touched by this change?

[JohnTitor]

I’m not sure where and how add a test, advise me?

[oli-obk]

Tests for diagnostics are added in src/test/ui. Most likely there's already a test. You can find the preexisting test by running ./x.py test src/test/ui --stage 1 --bless and wait for a failing test. If all of them are passing, search for allow_internal_unsafe and create a new test next to the existing tests. The test's body can probably just be the example from the issue.

[JohnTitor]

All of tests were passed. I searched for allow_internal_unsafe, found the test src/test/ui/feature-gates/feature-gate-allow-internal-unsafe-nested-macro.rs. But I added the function in librustc_lint, so I think it may good to add a test in src/test/ui/lint. Which is better, or is there a better way?

[oli-obk]

Yes src/test/ui/lin is a good place

[JohnTitor]

OK. I added the test in src/test/ui/lint, it's body is here:

#![forbid(unsafe_code)]
#![feature(allow_internal_unsafe)]

#[allow_internal_unsafe]
macro_rules! evil {
    ($e:expr) => {
        unsafe {
            $e
        }
    }
}

fn main() {
    println!("Hello, world! {}", evil!(*(0 as *const u8)));
}

But I got no stdout and stderr.

stdout:
------------------------------------------

------------------------------------------
stderr:
------------------------------------------

------------------------------------------

thread '[ui] ui\lint\lint-forbid-allow-internal-unsafe.rs' panicked at 'explicit panic', src\tools\compiletest\src\runtest.rs:3245:9


failures:
    [ui] ui\lint\lint-forbid-allow-internal-unsafe.rs

What did I do wrong?

[JohnTitor]

@oli-obk I’ve done all I can. Could you review my code?

• I don't know how to separate error comment into some lines in the test, so I made the error message short.
• I changed the files other than builtin.rs, any problem?
  • In lint-unsafe-code.rs, two errors has occurred at the same time, is this bad?

[oli-obk]

I don't know how to separate error comment into some lines in the test, so I made the error message short.

You don't need to specify the entire message, just a part of it is enough.

I changed the files other than builtin.rs, any problem?

Nope, lgtm

In lint-unsafe-code.rs, two errors has occurred at the same time, is this bad?

Should be fixed by the None change suggested above

[oli-obk]

Wonderful. Thanks for going all the way and making it an EarlyLintPass.

@bors r+

[bors]

📌 Commit bd1551e has been approved by oli-obk