From 9e9cb021ab6145965f44bf4b67424ad90655db17 Mon Sep 17 00:00:00 2001
From: cpw <cpw+github@weeksfamily.ca>
Date: Tue, 1 May 2018 05:05:37 +0100
Subject: [PATCH] Clean up broken aliases caused by registry bug #4894. (#4909)

---
 .../net/minecraftforge/registries/ForgeRegistry.java  | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/main/java/net/minecraftforge/registries/ForgeRegistry.java b/src/main/java/net/minecraftforge/registries/ForgeRegistry.java
index 2cf727843d..1e06da1cdd 100644
--- a/src/main/java/net/minecraftforge/registries/ForgeRegistry.java
+++ b/src/main/java/net/minecraftforge/registries/ForgeRegistry.java
@@ -856,7 +856,16 @@ public class ForgeRegistry<V extends IForgeRegistryEntry<V>> implements IForgeRe
                 }
                 else
                 {
-                    ret.aliases.put(new ResourceLocation(comp.getString("K")), new ResourceLocation(v));
+                    ResourceLocation aliask = new ResourceLocation(comp.getString("K"));
+                    ResourceLocation aliasv = new ResourceLocation(v);
+                    if (aliasv.equals(aliask))
+                    {
+                        FMLLog.log.warn("Found unrecoverable 4894 bugged alias/override: {} -> {}, skipping.", aliask, aliasv);
+                    }
+                    else
+                    {
+                        ret.aliases.put(aliask, aliasv);
+                    }
                 }
             });