First, make sure that `add_methods` cannot trigger another userdata registry
insert, causing an unintended panic. Second, remove `RefCell` surrounding
userdata hashmap, as this change makes it no longer needed. Third, add a
`RefCell` around `Callback` because FnMut means that callbacks cannot recurse
into themselves, and panic appropriately when this happens. This should
eventually be turned into an error.
CallbackError now, instead of displaying the cause description, instead prints
"callback error: <traceback>". Since the cause is already in the cause chain of
the error, this avoids repeatedly printing the cause of callback errors along
the chain, and also actually prints the callback when using Display on each
error in the chain.
The stock Lua interpreter doesn't do this either. AFAIK the "base" library is supposed to be loaded into "_G" only as it contains functions like `assert` and `error`.
This cannot be accomplished without using unsafe code, which justifies this addition in my opinion.
Also changes "null" to "nul" to be in sync with `std::ffi` docs. Naming is derived from `CStr::to_bytes_with_nul`, using `as_*` instead of `to_*` since this isn't doing any computation.
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.
kyren