List functions or lines that can panic

[alexchandel]

(Imported from geiger-rs/cargo-geiger#50 for want of a call-stack graph).

Panics are very overused in libraries, and can unexpectedly crash unwary users and poison their mutexes. We need something to warn unsuspecting consumers which of their functions is most "explosive" / invokes the most panics, and which libraries are the cause. Without this, it's impossible for large codebases to be certain their threads won't panic and explode, nor even for small codebases that use complex libraries with many dependencies to be certain how explosive their calls truly are.

Ideally, panics provably unreachable by the compiler should not be reported. And a flag to suppress slicing panics is worthy of consideration.

[laudiacay]

Some useful one-liners for this in the comments of this: https://www.reddit.com/r/rust/comments/g9mw57/oneliner_to_correctly_list_all_uses_ofunsafe_in/