Small Enum/EnumType cleanups for consistency (#759)

packages/types/src/codec/Enum.ts

@@ -65,6 +65,13 @@ export default class Enum extends Base<number> implements Codec {
     return 1;
   }
 
+  /**
+   * @description Returns the index for this value (equivalent to toNumber)
+   */
+  get index (): number {
+    return this.raw;
+  }
+
   /**
    * @description Checks if the value is an empty value (always false)
    */

packages/types/src/codec/EnumType.ts

@@ -133,7 +133,7 @@ export default class EnumType<T> extends Base<Codec> implements Codec {
    * @description Checks if the Enum points to a [[Null]] type
    */
   get isNone (): boolean {
-    return this.raw instanceof Null;
+    return this.isNull;
   }
 
   /**