项目初始化

src/app/core/module-import-guard.ts

@@ -0,0 +1,6 @@
+// https://angular.io/guide/styleguide#style-04-12
+export function throwIfAlreadyLoaded(parentModule: any, moduleName: string): void {
+  if (parentModule) {
+    throw new Error(`${moduleName} has already been loaded. Import Core modules in the AppModule only.`);
+  }
+}