Always treating warnings as errors makes development annoying ("ugh I don't want to fix this right now"), but ignoring them quickly leaves them unfixed and shines a bad light on the project when other people want build it ("hmm, this crate's a little to... yellow for my taste"). I've found that this is pretty much a perfect middle ground (even though rlua doesn't require CI to pass before merging PRs).
setmetatable now wraps a __gc method in a cclosure that aborts on error, also
'debug' library is no longer provided. We could provide just the subset of the
debug library that is sound, though.
Since this is `rlua::Error`, it should be clear that it refers to
Lua-related errors. Downstream crates want to define their own error
enums, which can add a prefix like "lua error:" to disambiguate.
Previously, the traceback would be printed, but not the actual error.
I've removed traceback printing completely, not sure if that's a good
idea. A `Display` impl that outputs multiple lines feels weird.
Also rename to/from/pack/unpack to pack/unpack/pack_multi/unpack_multi, I don't
know if this makes their usage clearer, and it IS a bit confusing that I'm
changing the meaning of the words 'pack' and 'unpack'
This was only allowed for `UserData` implementors that are also `Copy`.
This relaxes the requirement to be `Clone` instead.
While `Copy` makes sense to prevent allocations and other potentially
costly operations, other `FromLua` impls already do pretty expensive
stuff, so this seems worth it.
I didn't yet document *everything* there is to say (in particular, how
exactly custom Rust errors can be passed through Lua), but I've some
changes to this type in mind that I'll do next.
In resume_with_traceback, always use the coroutine stack for error handling so
we don't miss panics, in both _with_traceback functions remove the temporary
traceback entry from the stack.
kyren