I've seen a few comments mentioning the lack of static type checking, so I think this is probably a good time to mention my new(ish) project Teal:

https://github.com/teal-language/tl

It's a statically typed dialect of Lua, which is compatible with all modern Lua versions.

The core compiler itself is one tl.lua file which can be added to any Lua project, and includes a Lua package loader that makes Lua's `require()` support .tl files, and there's also a tl CLI for generating .lua from .tl files.