What happens if a dependency of mine unwrap()s or expect()s something that is an error or isn't there? What should I do?

How was I informed as a user? It's not in the type signature.

Sounds like I get to indeterminately crash at runtime and have a fun time debugging.

That would require an effects system[0] like Koka's[1]. Then one could not only express the absence of panics but also allocations, infinite loops and various other undesirable effects within some call-trees. This is a desirable feature, but an enormous undertaking.

Absent that there are hacks like no_panic[2]

[0] https://blog.yoshuawuyts.com/extending-rusts-effect-system/ [1] https://koka-lang.github.io/koka/doc/book.html#why-effects [2] https://crates.io/crates/no-panic

Same thing that would happen if it did a match statement and panicked. The problem is the panic, not the unwrap.

I don’t think you can ever completely eliminate panics, because there are always going to be some assumptions in code that will be surprisingly violated, because bugs exist. What if the heap allocator discovers the heap is corrupted? What if you reference memory that’s paged out and the disk is offline? (That one’s probably not turned into a panic, but it’s the same principle.)

Not explicit enough, apparently.