From 29d52e065f7e52cf08f2dac095bd8a86d90d13fb Mon Sep 17 00:00:00 2001
From: Kurt <kaphotics@gmail.com>
Date: Sat, 16 Nov 2019 09:00:05 -0800
Subject: [PATCH] Don't generate invalid sister-pair eggs

---
 .../Encounters/Generator/EncounterEggGenerator.cs        | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/PKHeX.Core/Legality/Encounters/Generator/EncounterEggGenerator.cs b/PKHeX.Core/Legality/Encounters/Generator/EncounterEggGenerator.cs
index 75f955d09..d46ad290b 100644
--- a/PKHeX.Core/Legality/Encounters/Generator/EncounterEggGenerator.cs
+++ b/PKHeX.Core/Legality/Encounters/Generator/EncounterEggGenerator.cs
@@ -36,7 +36,7 @@ public static IEnumerable<EncounterEgg> GenerateEggs(PKM pkm, IReadOnlyList<DexL
             if (baseSpecies <= max)
             {
                 yield return new EncounterEgg { Version = ver, Level = lvl, Species = baseSpecies };
-                if (gen > 5 && (pkm.WasTradedEgg || all))
+                if (gen > 5 && (pkm.WasTradedEgg || all) && HasOtherGamePair(ver))
                     yield return new EncounterEgg { Version = GetOtherTradePair(ver), Level = lvl, Species = baseSpecies };
             }
 
@@ -47,7 +47,7 @@ public static IEnumerable<EncounterEgg> GenerateEggs(PKM pkm, IReadOnlyList<DexL
             if (other <= max)
             {
                 yield return new EncounterEggSplit { Version = ver, Level = lvl, Species = other, OtherSpecies = baseSpecies };
-                if (gen > 5 && (pkm.WasTradedEgg || all))
+                if (gen > 5 && (pkm.WasTradedEgg || all) && HasOtherGamePair(ver))
                     yield return new EncounterEggSplit { Version = GetOtherTradePair(ver), Level = lvl, Species = other, OtherSpecies = baseSpecies };
             }
         }
@@ -61,5 +61,10 @@ private static GameVersion GetOtherTradePair(GameVersion ver)
                 return ver + 2;
             return ver - 2;
         }
+
+        private static bool HasOtherGamePair(GameVersion ver)
+        {
+            return ver < GameVersion.GP; // lgpe and sw/sh don't have a sister pair
+        }
     }
 }