pub type LuaCFnPtr = usize;Expand description
Opaque registry index into GlobalState.c_functions, where the real
lua_CFunction (fn(&mut LuaState) -> Result<usize, LuaError>) is stored.
Lua-types can’t reference LuaState without a circular dep, so we keep
the closure variant type-erased here and resolve through the registry at
call time.