I think the main problem here is that there are several semantic differences between 5.3's and LuaJIT's integers which would make this a bit dodgy; eg. rounding

I think the main problem here is that there are several semantic differences between 5.3's and LuaJIT's integers which would make this a bit dodgy; eg. rounding behavior and mixed float-integer arithmetic are different. IMO 5.3 should have done what LuaJIT did and require a suffix for 64-bit integer literals (say `L` to avoid conflict with LuaJIT's `LL`). Given how rarely Lua code needs true integers this large, that probably would have worked better. It also would have avoided the gotchas of porting code to 5.3 where the integral numbers you never add `.0` to are suddenly real integers instead of floats. I'd love for LuaJIT to get 5.3's bitwise ops but the semantic differences between the integer implementations would make this interesting to say the least.