better error message when light userdata is used instead of a

full userdata

ldblib.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ldblib.c,v 1.123 2010/07/02 11:38:13 roberto Exp roberto $
+** $Id: ldblib.c,v 1.124 2010/07/25 15:18:19 roberto Exp roberto $
 ** Interface from Lua to its debug API
 ** See Copyright Notice in lua.h
 */
@@ -44,15 +44,22 @@ static int db_setmetatable (lua_State *L) {
 }
 
 
+static void checkudata (lua_State *L, int narg) {
+  if (lua_type(L, narg) == LUA_TLIGHTUSERDATA)
+    luaL_argerror(L, narg, "full userdata expected, got light userdata");
+  luaL_checktype(L, narg, LUA_TUSERDATA);
+}
+
+
 static int db_getuservalue (lua_State *L) {
-  luaL_checktype(L, 1, LUA_TUSERDATA);
+  checkudata(L, 1);
   lua_getuservalue(L, 1);
   return 1;
 }
 
 
 static int db_setuservalue (lua_State *L) {
-  luaL_checktype(L, 1, LUA_TUSERDATA);
+  checkudata(L, 1);
   if (!lua_isnoneornil(L, 2))
     luaL_checktype(L, 2, LUA_TTABLE);
   lua_settop(L, 2);