Compiling error

I am having this exact same problem. I have followed the video exactly and its still coming up with that same error about not being able to read from file "WCSIncs War3Source_L4D_Interface"

Yes I have this file in the correct folder. I am a beginner programmer so not sure if there is something wrong with that file. Please take a look at it and see if it needs any adjustments.

/**
* File: War3Source_L4D_Interface.inc
* Description: Functions and stuff to make L4D specific races and whatnot
* Author(s): Glider
*
*/

#include <sdktools>

#include "W3SIncs/constants"

/**
* Returns true if a infected is making love to a client.
*
* Bug: If you kick the infected then this function will still return true
* for the client until he gets properly freed from a infected attack.
*/
native bool:War3_L4D_IsHelpless(client);

stock bool:War3_IsL4DEngine() {
   return (War3_GetGame() == Game_L4D || War3_GetGame() == Game_L4D2);
}

stock bool:War3_IsPlayerIncapped(client)
{
   if (GetEntProp(client, Prop_Send, "m_isIncapacitated", 1)) return true;
   return false;
}

stock bool:War3_IsL4DZombieEntity(iEntity) {
if (War3_IsL4DEngine()) {
return (War3_IsCommonInfected(iEntity) || War3_IsWitch(iEntity));
}

return false;
}

stock bool:War3_IsCommonInfected(iEntity)
{
if(iEntity > 0 && IsValidEntity(iEntity) && IsValidEdict(iEntity))
{
decl String:strClassName[64];
GetEdictClassname(iEntity, strClassName, sizeof(strClassName));

return StrEqual(strClassName, "infected");
}
return false;
}

stock bool:War3_IsUncommonInfected(iEntity)
{
if(iEntity > 0 && IsValidEntity(iEntity) && IsValidEdict(iEntity))
{
      decl String:ModelName[128];
      GetEntPropString(iEntity, Prop_Data, "m_ModelName", ModelName, sizeof(ModelName));

      return (StrEqual(ModelName, "models/infected/common_male_riot.mdl") ||
            StrEqual(ModelName, "models/infected/common_male_ceda.mdl") ||
            StrEqual(ModelName, "models/infected/common_male_clown.mdl") ||
            StrEqual(ModelName, "models/infected/common_male_mud.mdl") ||
            StrEqual(ModelName, "models/infected/common_male_roadcrew.mdl") ||
            StrEqual(ModelName, "models/infected/common_male_jimmy.mdl") ||
            StrEqual(ModelName, "models/infected/common_male_fallen_survivor.mdl"));
}
return false;
}

stock bool:War3_IsWitch(iEntity)
{
if(iEntity > 0 && IsValidEntity(iEntity) && IsValidEdict(iEntity))
{
decl String:strClassName[64];
GetEdictClassname(iEntity, strClassName, sizeof(strClassName));
return StrEqual(strClassName, "witch");
}
return false;
}

// To check if an infected in versus hasn't spawned yet
stock bool:IsPlayerGhost(client)
{
   if (GetEntProp(client, Prop_Send, "m_isGhost", 1) == 1)
   {
      return true;
   }

   return false;
}

stock GetSurvivorTempHealth(client)
{
   new temphp = RoundToCeil(GetEntPropFloat(client, Prop_Send, "m_healthBuffer") - ((GetGameTime() - GetEntPropFloat(client, Prop_Send, "m_healthBufferTime")) * GetConVarFloat(FindConVar("pain_pills_decay_rate")))) - 1;
   return temphp > 0 ? temphp : 0;
}

stock SetSurvivorTempHealth(client, hp)
{
   SetEntPropFloat(client, Prop_Send, "m_healthBufferTime", GetGameTime());
   new Float:newOverheal = hp * 1.0;
   SetEntPropFloat(client, Prop_Send, "m_healthBuffer", newOverheal);
}

stock GetMaxMagSize(const String:weapon[])
{
   if (War3_IsL4DEngine())
   {
      if ((StrEqual(weapon, "weapon_rifle", false)) || (StrEqual(weapon, "weapon_rifle_sg552", false)))
      {
         return 50;
      }
      else if (StrEqual(weapon, "weapon_rifle_ak47", false))
      {
         return 40;
      }
      else if (StrEqual(weapon, "weapon_rifle_desert", false))
      {
         return 60;
      }
      else if (StrEqual(weapon, "weapon_autoshotgun", false) || StrEqual(weapon, "weapon_shotgun_spas", false))
      {
         return 10;
      }
   }

   return 0;
}

stock GetMaxBackupAmmo(const String:weapon[])
{
   if (War3_IsL4DEngine())
   {
      if (StrEqual(weapon, "weapon_rifle", false) || StrEqual(weapon, "weapon_rifle_ak47", false) || StrEqual(weapon, "weapon_rifle_desert", false) || StrEqual(weapon, "weapon_rifle_sg552", false))
      {
         return GetConVarInt(FindConVar("ammo_assaultrifle_max"));
      }
      else if (StrEqual(weapon, "weapon_smg", false) || StrEqual(weapon, "weapon_smg_silenced", false) || StrEqual(weapon, "weapon_smg_mp5", false))
      {
         return GetConVarInt(FindConVar("ammo_smg_max"));
      }
      else if (StrEqual(weapon, "weapon_pumpshotgun", false) || StrEqual(weapon, "weapon_shotgun_chrome", false))
      {
         return GetConVarInt(FindConVar("ammo_shotgun_max"));
      }
      else if (StrEqual(weapon, "weapon_autoshotgun", false) || StrEqual(weapon, "weapon_shotgun_spas", false))
      {
         return GetConVarInt(FindConVar("ammo_autoshotgun_max"));
      }
      else if (StrEqual(weapon, "weapon_hunting_rifle", false))
      {
         return GetConVarInt(FindConVar("ammo_huntingrifle_max"));
      }
      else if (StrEqual(weapon, "weapon_sniper_military", false) || StrEqual(weapon, "weapon_sniper_awp", false) || StrEqual(weapon, "weapon_sniper_scout", false))
      {
         return GetConVarInt(FindConVar("ammo_sniperrifle_max"));
      }
      else if (StrEqual(weapon, "weapon_grenade_launcher", false))
      {
         return GetConVarInt(FindConVar("ammo_grenadelauncher_max"));
      }
      else if (StrEqual(weapon, "weapon_rifle_m60", false))
      {
         return 150;
      }
   }

   return 0;
}

#include "W3SIncs/stocks_precache"
#include "W3SIncs/stocks_misc"