Some cleanup of CanSeeOrDetect code.

src/server/game/Entities/Object/Object.cpp

@@ -1587,14 +1587,6 @@ bool Position::IsPositionValid() const
     return Trinity::IsValidMapCoord(m_positionX, m_positionY, m_positionZ, m_orientation);
 }
 
-bool WorldObject::isValid() const
-{
-    if (!IsInWorld())
-        return false;
-
-    return true;
-}
-
 float WorldObject::GetGridActivationRange() const
 {
     if (ToPlayer())
@@ -1638,7 +1630,7 @@ bool WorldObject::canSeeOrDetect(WorldObject const* obj, bool ignoreStealth, boo
     if (this == obj)
         return true;
 
-    if (!obj->isValid())
+    if (obj->IsNeverVisible())
         return false;
 
     if (GetMap() != obj->GetMap())
@@ -1704,7 +1696,7 @@ bool WorldObject::canSeeOrDetect(WorldObject const* obj, bool ignoreStealth, boo
             return false;
     }
 
-    if (!obj->isVisibleForInState(this))
+    if (obj->IsInvisibleDueToDespawn())
         return false;
 
     if (!canDetect(obj, ignoreStealth))