Hlua no functions with arguments workaround

fn.rs

/// Call the given lua function in the prelude table with the given arguments.
pub fn call_fn(interpreter: &mut Lua,
               fn_to_call: &str,
               args: Vec<AnyLuaValue>)
               -> Result<Option<AnyLuaValue>, LuaError> {
let mut prelude_table: LuaTable<_> = interpreter
                                         .get("prelude")
                                         .expect("The prelude_table wasn't found. Was \
                                                  the prelude properly loaded?");
    prelude_table.set("fn_to_call", fn_to_call);
    prelude_table.set("args", args);
    {
        let mut call_fn_lua: LuaFunction<_> = prelude_table.get("call_fn")
                                                           .expect("prelude.call_prelude_fn not \
                                                                    found. Was the prelude \
                                                                    properly loaded?");
        try!(call_fn_lua.call::<()>());
    }
    let ret: Option<AnyLuaValue> = prelude_table.get("ret");
    Ok(ret)
}

prelude.lua

prelude = {}

function prelude.call_fn ()
    -- Assumes that prelude.fn_to_call is a string pointing to the function to call, and
    -- prelude.args is the arguments to that function. The return value of the function is then placed in
    -- prelude.ret.
    -- This function is used to call functions with arguments in rust,
    -- since it isn't exposed in hlua.
    if next(prelude.args) ~= nil then
        local ret = _G[prelude.fn_to_call](unpack(prelude.args))
    else
        local ret = _G[prelude.fn_to_call]()
    end
    prelude.ret = ret
end