Highlight functions that can panic if misused

[steven-joruk]

Similar to issue #190 I think it would be useful to indicate functions that can panic if misused. Sometimes it might not be obvious that it's even possible to misuse a certain function, so it would be a good hint for users to properly read its documentation.

Clippy has an open issue about warning when a function panics but doesn't have a # Panics section in the rustdoc: rust-lang/rust-clippy#1974. That approach might be a reasonable way to determine if a function should be highlighted.

[matklad]

Hm, now that I think about this more, this seems pretty niche, and unlikely to be implemented in rust-analyzer proper. One day, once we have extension API, there might be a 3rd-party tool for this, but now, in the interst of keeping the issue list focused on actionable items I am going to close.