Function get_from_lua_state

library/include/DataFuncs.h:50–62

    // will throw if lua code tries to pass a null pointer
    template<typename T> requires std::is_reference_v<T>
    T get_from_lua_state(lua_State* L, int idx)
    {
        using DFHack::LuaWrapper::field_error;
        using DFHack::LuaWrapper::UPVAL_METHOD_NAME;
        using Ptr = std::add_pointer_t<std::remove_reference_t<T>>;
        Ptr ptr{};
        df::identity_traits<Ptr>::get()->lua_write(L, UPVAL_METHOD_NAME, &ptr, idx);
        if (ptr == nullptr)
        {
            field_error(L, UPVAL_METHOD_NAME, "cannot convert null pointer to reference", "call");
        }
        return *ptr;
    }

    // handle call-by-value function arguments. only semi-regular types are allowed
    // (semi-regular covers copyable and default-constructible)