refactor: replace const enum with union type

types/eslint-plugin-prettier/eslint-plugin-prettier-tests.ts

@@ -13,13 +13,13 @@ utils.generateDifferences('abc', 'def').forEach(difference => {
     } = difference;
 
     switch (operation) {
-        case utils.DifferenceOperation.Delete:
+        case 'delete':
             log('delete', offset, deleteText);
             break;
-        case utils.DifferenceOperation.Insert:
+        case 'insert':
             log('insert', offset, insertText);
             break;
-        case utils.DifferenceOperation.Replace:
+        case 'replace':
             log('replace', offset, insertText, deleteText);
             break;
         default:

types/eslint-plugin-prettier/index.d.ts

@@ -2,7 +2,6 @@
 // Project: https://github.com/prettier/eslint-plugin-prettier
 // Definitions by: Ika <https://github.com/ikatyang>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
-// TypeScript Version: 2.4
 
 /**
  * Converts invisible characters to a commonly recognizable visible form.
@@ -21,16 +20,10 @@ export function generateDifferences(
 ): Difference[];
 
 export interface Difference {
-    operation: DifferenceOperation;
+    operation: 'insert' | 'delete' | 'replace';
     offset: number;
     insertText?: string;
     deleteText?: string;
 }
 
-export const enum DifferenceOperation {
-    Insert = 'insert',
-    Delete = 'delete',
-    Replace = 'replace',
-}
-
 export const rules: any;