bug: ipairs does not work on userdata if LUA_COMPAT

Subject: bug: ipairs does not work on userdata if LUA_COMPAT_IPAIRS is enabled
From: Tarek Sabet &lt;undefdev@ ... &gt;
Date: Mon, 18 Jul 2016 00:08:58 +0200

Hi,

I have found an error that forces the programmer to write backwards compatible code if the target is default-compiled Lua 5.3.x.

If LUA_COMPAT_IPAIRS is defined (which it is by default), Lua always ignores __index and only checks for __ipairs.

Therefore ipairs does not work for userdata with an adequate __index field.

Details:

Ibaselib.c:258 luaB_ipairs will result in a call to pairsmeta.
pairsmeta calls luaL_checktype(L, 1, LUA_TTABLE) instead of luaL_checkany which results in this problem.

undef