When available, use metafield '__name' in error messages

ldebug.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ldebug.c,v 2.117 2015/11/02 18:48:07 roberto Exp roberto $
+** $Id: ldebug.c,v 2.118 2015/12/16 16:40:07 roberto Exp roberto $
 ** Debug Interface
 ** See Copyright Notice in lua.h
 */
@@ -564,7 +564,7 @@ static const char *varinfo (lua_State *L, const TValue *o) {
 
 
 l_noret luaG_typeerror (lua_State *L, const TValue *o, const char *op) {
-  const char *t = objtypename(o);
+  const char *t = luaT_objtypename(L, o);
   luaG_runerror(L, "attempt to %s a %s value%s", op, t, varinfo(L, o));
 }
 
@@ -596,9 +596,9 @@ l_noret luaG_tointerror (lua_State *L, const TValue *p1, const TValue *p2) {
 
 
 l_noret luaG_ordererror (lua_State *L, const TValue *p1, const TValue *p2) {
-  const char *t1 = objtypename(p1);
-  const char *t2 = objtypename(p2);
-  if (t1 == t2)
+  const char *t1 = luaT_objtypename(L, p1);
+  const char *t2 = luaT_objtypename(L, p2);
+  if (strcmp(t1, t2) == 0)
     luaG_runerror(L, "attempt to compare two %s values", t1);
   else
     luaG_runerror(L, "attempt to compare %s with %s", t1, t2);

ltm.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ltm.c,v 2.35 2015/11/02 18:48:07 roberto Exp roberto $
+** $Id: ltm.c,v 2.36 2015/11/03 15:47:30 roberto Exp roberto $
 ** Tag methods
 ** See Copyright Notice in lua.h
 */
@@ -83,6 +83,22 @@ const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o, TMS event) {
 }
 
 
+/*
+** Return the name of the type of an object. For tables and userdata
+** with metatable, use their '__name' metafield, if present.
+*/
+const char *luaT_objtypename (lua_State *L, const TValue *o) {
+  Table *mt;
+  if ((ttistable(o) && (mt = hvalue(o)->metatable) != NULL) ||
+      (ttisfulluserdata(o) && (mt = uvalue(o)->metatable) != NULL)) {
+    const TValue *name = luaH_getshortstr(mt, luaS_new(L, "__name"));
+    if (ttisstring(name))  /* is '__name' a string? */
+      return getstr(tsvalue(name));  /* use it as type name */
+  }
+  return ttypename(ttnov(o));  /* else use standard type name */
+}
+
+
 void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,
                   const TValue *p2, TValue *p3, int hasres) {
   ptrdiff_t result = savestack(L, p3);

ltm.h

@@ -1,5 +1,5 @@
 /*
-** $Id: ltm.h,v 2.20 2014/06/10 18:53:18 roberto Exp roberto $
+** $Id: ltm.h,v 2.21 2014/10/25 11:50:46 roberto Exp roberto $
 ** Tag methods
 ** See Copyright Notice in lua.h
 */
@@ -51,11 +51,12 @@ typedef enum {
 #define fasttm(l,et,e)	gfasttm(G(l), et, e)
 
 #define ttypename(x)	luaT_typenames_[(x) + 1]
-#define objtypename(x)	ttypename(ttnov(x))
 
 LUAI_DDEC const char *const luaT_typenames_[LUA_TOTALTAGS];
 
 
+LUAI_FUNC const char *luaT_objtypename (lua_State *L, const TValue *o);
+
 LUAI_FUNC const TValue *luaT_gettm (Table *events, TMS event, TString *ename);
 LUAI_FUNC const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o,
                                                        TMS event);