Replace default backing map of NBT tags in more compatible way

Related: #111

Author: embeddedt

common/src/main/java/org/embeddedt/modernfix/common/mixin/perf/nbt_memory_usage/CompoundTagMixin.java

@@ -6,27 +6,24 @@
 import org.spongepowered.asm.mixin.*;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
-import org.spongepowered.asm.mixin.injection.Redirect;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
 import java.util.Map;
 
 @Mixin(CompoundTag.class)
 public class CompoundTagMixin {
-    @Shadow @Final @Mutable
+    @Shadow @Final
     private Map<String, Tag> tags;
 
     /**
-     * Ensure that the backing map is always a CanonizingStringMap.
+     * Ensure that the default backing map is a CanonizingStringMap.
      */
-    @Redirect(method = "<init>(Ljava/util/Map;)V", at = @At(value = "FIELD", target = "Lnet/minecraft/nbt/CompoundTag;tags:Ljava/util/Map;", ordinal = 0))
-    private void replaceTagMap(CompoundTag tag, Map<String, Tag> incomingMap) {
-        if(incomingMap instanceof CanonizingStringMap)
-            this.tags = incomingMap;
-        else {
-            this.tags = new CanonizingStringMap<>();
-            this.tags.putAll(incomingMap);
-        }
+    @ModifyArg(method = "<init>()V", at = @At(value = "INVOKE", target = "Lnet/minecraft/nbt/CompoundTag;<init>(Ljava/util/Map;)V"), index = 0)
+    private static Map<String, Tag> useCanonizingStringMap(Map<String, Tag> incoming) {
+        CanonizingStringMap<Tag> newMap = new CanonizingStringMap<>();
+        newMap.putAll(incoming);
+        return newMap;
     }
 
     /**