Add OriginalArg annotation

The dummy argument removal code is going to fiddle with the argument
lists (and so could manual refactoring).

deob-annotations/src/main/java/dev/openrs2/deob/annotation/OriginalArg.java

@@ -0,0 +1,9 @@
+package dev.openrs2.deob.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Target;
+
+@Target({ ElementType.PARAMETER })
+public @interface OriginalArg {
+	int value();
+}

deob/src/main/java/dev/openrs2/deob/transform/OriginalNameTransformer.java

@@ -4,6 +4,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 import dev.openrs2.asm.Transformer;
+import dev.openrs2.deob.annotation.OriginalArg;
 import dev.openrs2.deob.annotation.OriginalClass;
 import dev.openrs2.deob.annotation.OriginalMember;
 import org.objectweb.asm.Type;
@@ -29,6 +30,12 @@ public final class OriginalNameTransformer extends Transformer {
 		return annotation;
 	}
 
+	private static AnnotationNode createOriginalArgAnnotation(int index) {
+		var annotation = new AnnotationNode(Type.getDescriptor(OriginalArg.class));
+		annotation.values = List.of("value", index);
+		return annotation;
+	}
+
 	@Override
 	public void transformClass(ClassNode clazz) {
 		if (clazz.invisibleAnnotations == null) {
@@ -45,6 +52,7 @@ public final class OriginalNameTransformer extends Transformer {
 		field.invisibleAnnotations.add(createOriginalMemberAnnotation(clazz.name, field.name, field.desc));
 	}
 
+	@SuppressWarnings("unchecked")
 	@Override
 	public void transformMethod(ClassNode clazz, MethodNode method) {
 		if (method.name.equals("<init>") || method.name.equals("<clinit>")) {
@@ -55,5 +63,17 @@ public final class OriginalNameTransformer extends Transformer {
 			method.invisibleAnnotations = new ArrayList<>();
 		}
 		method.invisibleAnnotations.add(createOriginalMemberAnnotation(clazz.name, method.name, method.desc));
+
+		int args = Type.getArgumentTypes(method.desc).length;
+		if (method.invisibleParameterAnnotations == null) {
+			method.invisibleParameterAnnotations = (List<AnnotationNode>[]) new List<?>[args];
+		}
+		for (int i = 0; i < method.invisibleParameterAnnotations.length; i++) {
+			var annotations = method.invisibleParameterAnnotations[i];
+			if (annotations == null) {
+				annotations = method.invisibleParameterAnnotations[i] = new ArrayList<>();
+			}
+			annotations.add(createOriginalArgAnnotation(i));
+		}
 	}
 }