Core/Spells: Reinstate helperfunction removed in commit 0e3607df (with a new functionname to make more sense out of it), and adjust the remaining code slightly to accomodate that.

src/server/game/Entities/Player/Player.cpp

@@ -25085,6 +25085,13 @@ uint32 Player::CalculateTalentsPoints() const
     return uint32(talentPointsForLevel * sWorld->getRate(RATE_TALENT));
 }
 
+bool Player::canFlyInZone(uint32 mapid, uint32 zone) const
+{
+    // continent checked in SpellInfo::CheckLocation at cast and area update
+    uint32 v_map = GetVirtualMapForMapAndZone(mapid, zone);
+    return v_map != 571 || HasSpell(54197); // 54197 = Cold Weather Flying
+}
+
 void Player::LearnSpellHighestRank(uint32 spellid)
 {
     LearnSpell(spellid, false);

src/server/game/Entities/Player/Player.h

@@ -2136,6 +2136,8 @@ class Player : public Unit, public GridObject<Player>
         void SetFallInformation(uint32 time, float z);
         void HandleFall(MovementInfo const& movementInfo);
 
+        bool canFlyInZone(uint32 mapid, uint32 zone) const;
+
         void SetClientControl(Unit* target, bool allowMove);
 
         void SetMover(Unit* target);

src/server/game/Spells/SpellInfo.cpp

@@ -1482,15 +1482,12 @@ SpellCastResult SpellInfo::CheckLocation(uint32 map_id, uint32 zone_id, uint32 a
             case SPELL_AURA_MOD_INCREASE_MOUNTED_FLIGHT_SPEED:
             case SPELL_AURA_FLY:
             {
-                if (player)
+                SkillLineAbilityMapBounds bounds = sSpellMgr->GetSkillLineAbilityMapBounds(Id);
+                for (SkillLineAbilityMap::const_iterator skillIter = bounds.first; skillIter != bounds.second; ++skillIter)
                 {
-                    SkillLineAbilityMapBounds bounds = sSpellMgr->GetSkillLineAbilityMapBounds(Id);
-                    for (SkillLineAbilityMap::const_iterator skillIter = bounds.first; skillIter != bounds.second; ++skillIter)
-                    {
-                        // spell 54197 (Cold Weather Flying) is a prereq for flying in Northrend
-                        if (skillIter->second->skillId == SKILL_MOUNTS && player->GetMapId() != 571 && !player->HasSpell(54197))
-                            return SPELL_FAILED_INCORRECT_AREA; // maybe: SPELL_CUSTOM_ERROR_CANT_USE_THAT_MOUNT
-                    }
+                    if (skillIter->second->skillId == SKILL_MOUNTS)
+                        if (player && !player->canFlyInZone(map_id, zone_id))
+                            return SPELL_FAILED_INCORRECT_AREA;
                 }
             }
         }