Statically typed Lua
I am looking for a Lua front-end compiler that is type-checked at compile time, but outputs standard Lua 5.1 byte-code (that has only run-time types). What I want is a decent amount of static, compile-time syntactic analysis and optional typing, to detect trivial errors sooner than run-time. The resulting byte-code would have to play nicely with existing Lua byte-code that was compiled with the standard LoadString().
To be clear -- any difference would only occur at byte-compilation time. At runtime, the byte code would have no idea that anything different/unusual happened to it during the compile phase.
What I have in mind sounds a lot like ActionScript; I wouldn't even mind an ActionScript compiler that outputs Lua byte code!
Has anyone heard of such an effort? I've seen some references to using MetaLua to do this, but honestly I am not bright enough to make heads of tails of their documentation
Answer
In the summer of 2005 or thereabouts, I worked with an incredibly smart undergraduate student on the problem of doing some compile-time type inference for Lua, possibly assisted by annotations. This problem turns out to be incredibly hard! (My student wrote a short technical note, but it's not really intended for general circulation.)
If I wanted to solve the problem you have posed, with the twin constraints that it allow significant static type checking and that it interoperate with standard bytecode-compiled Lua code, I would design a new language from scratch to satisfy these two constraints. It would be a substantial amount of work but significantly easier than trying to retrofit a type system to Lua.