Add whitelist of safe intrinsics

[frazar]

This PR should fix #5996, where intrinsic operations where all marked as unsafe.

I'm rather new to this codebase, so I might be doing something very wrong. Please forgive me!

In particular, I'm not sure how to "check that we are in extern rust-intrinsics" as mentioned in this comment.

[lnicola]

Awesome, thanks for the PR :-). In other places we clone the repository and read the files from there, but this feels like such a huge wart TBH...

[lnicola]

Regarding the type of the extern block, the AST looks like this:

  EXTERN_BLOCK@0..28
    ABI@0..10
      EXTERN_KW@0..6 "extern"
      WHITESPACE@6..7 " "
      STRING@7..10 "\"C\""

[lnicola]

I think you can get the ABI node using extern_block.abi(), but there's no child for the type, only for the extern token. @matklad, we should probably add it to the AST? We're missing the accessor for it.

[bors]

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[matklad]

@lnicola good question! Turns out this needs a bit of design, I've put together #6308

[frazar]

Thank you for your feedback and comments. I think I addressed all points, except for the issue about checking the ABI name, which I guess is blocked on #6308.

Also, I'm not sure why CI failed for macos-latest.. It might be unrelated.

Let me know what should I do next!

[lnicola]

bors r=frazar

[bors]

Build succeeded:

• Rust (macos-latest)
• Rust (ubuntu-latest)
• Rust (windows-latest)
• TypeScript (ubuntu-latest)
• TypeScript (windows-latest)

[frazar]

Great! As a final note, would you mind adding the hacktoberfest-accepted label to this PR? Thanks!

[lnicola]

Sure, done.