add file

node_modules/vue-router/src/util/warn.js

@@ -0,0 +1,21 @@
+/* @flow */
+
+export function assert (condition: any, message: string) {
+  if (!condition) {
+    throw new Error(`[vue-router] ${message}`)
+  }
+}
+
+export function warn (condition: any, message: string) {
+  if (process.env.NODE_ENV !== 'production' && !condition) {
+    typeof console !== 'undefined' && console.warn(`[vue-router] ${message}`)
+  }
+}
+
+export function isError (err: any): boolean {
+  return Object.prototype.toString.call(err).indexOf('Error') > -1
+}
+
+export function isRouterError (err: any, errorType: ?string): boolean {
+  return isError(err) && err._isRouter && (errorType == null || err.type === errorType)
+}