Add lambda method detection

Author: JoJoDeveloping

src/main/java/de/oceanlabs/mcp/mcinjector/adaptors/ApplyMap.java

@@ -197,7 +197,11 @@ else if (tmp.getType() != AbstractInsnNode.LABEL)
     }
 
     private boolean isSynthetic(MethodNode mn){
-        if ((mn.access & Opcodes.ACC_SYNTHETIC) != 0) return true;
+        if ((mn.access & Opcodes.ACC_SYNTHETIC) != 0) {
+            //de-lambdaified methods may be synthetic but actually appear in sourcecode so their args still get renamed
+            //such methods are private and start with lambda$
+            return (mn.access & Opcodes.ACC_PRIVATE) == 0 || !mn.name.startsWith("lambda$");
+        }
 
         //check for special case pursuant to JLS 13.1.7
         //which specifies that are the one and only proper methods that may be generated and not be marked synthetic