Concat operator does only tries to invoke metamethod from lhs

[powercode]

The metamethod is probed in p1 (LHS) and, if not found in p1, p2 (RHS) in the C implementation.

static int call_binTM (lua_State *L, const TValue *p1, const TValue *p2,
                       StkId res, TMS event) {
  const TValue *tm = luaT_gettmbyobj(L, p1, event);  /* try first operand */
  if (ttisnil(tm))
    tm = luaT_gettmbyobj(L, p2, event);  /* try second operand */
  if (ttisnil(tm)) return 0;
  callTM(L, tm, p1, p2, res, 1);
  return 1;
}

This implementation does not try to find the metamethod in RHS:

internal static string RtConcatString(object[] args)
{
    if (Array.FindExists(args, a => a is LuaTable)) // do we have a table, then we use the metatable
        return RtConcatStringTable(args, 0);
    else
    {
        var strings = new string[args.Length];
        for (var i = 0; i < args.Length; i++)
            strings[i] = (string)RtConvertValue(args[i], typeof(string));
        return String.Concat(strings);
    }
} // func RtConcatString

This seems like a bug.