离子4离子角<ion button>不是已知元素

ionic start newApp blank --type=ionic-angular

ionic-angular .

{
  "name": "courier-app",
  "version": "0.0.1",
  "author": "Ionic Framework",
  "homepage": "http://ionicframework.com/",
  "private": true,
  "scripts": {
    "start": "ionic-app-scripts serve",
    "clean": "ionic-app-scripts clean",
    "build": "ionic-app-scripts build",
    "lint": "ionic-app-scripts lint"
  },
  "dependencies": {
    "@angular/animations": "5.2.11",
    "@angular/common": "5.2.11",
    "@angular/compiler": "5.2.11",
    "@angular/compiler-cli": "5.2.11",
    "@angular/core": "5.2.11",
    "@angular/forms": "5.2.11",
    "@angular/http": "5.2.11",
    "@angular/platform-browser": "5.2.11",
    "@angular/platform-browser-dynamic": "5.2.11",
    "@ionic-native/core": "~4.18.0",
    "@ionic-native/splash-screen": "~4.18.0",
    "@ionic-native/status-bar": "~4.18.0",
    "@ionic/storage": "2.2.0",
    "ionic-angular": "^3.9.3",
    "ionicons": "3.0.0",
    "rxjs": "5.5.11",
    "sw-toolbox": "3.6.0",
    "zone.js": "0.8.29"
  },
  "devDependencies": {
    "@ionic/app-scripts": "3.2.1",
    "typescript": "~2.6.2"
  },
  "description": "An Ionic project"
}

你可以清楚地看到 离子角 有最新版本3.9:

"ionic-angular": "^3.9.3"

这个 IonicModule 导入到 app.module.ts 不过,我设置了 LoginPage 作为要首先加载的根页:

@NgModule({
  declarations: [
    MyApp,
    HomePage,
    LoginPage
  ],
  imports: [
    BrowserModule,
    IonicModule.forRoot(MyApp)
  ],
  bootstrap: [IonicApp],
  entryComponents: [
    MyApp,
    HomePage,
    LoginPage
  ],
  providers: [
    StatusBar,
    SplashScreen,
    {provide: ErrorHandler, useClass: IonicErrorHandler}
  ]
})
export class AppModule {}

在app.component.ts中:

rootPage:any = LoginPage;

当我在登录页面中添加登录按钮时:

<ion-button (click)="login()">Login</ion-button>

我有个错误说:

<ion-button> is not a known element

post ,我将其更改为:

<button ion-button ...>Login</button>

但据我所知,离子4中组分的行为(不管是什么类型的)是 <ion-button> <button ion-button>

有没有遗漏进口,或者这只是离子4型离子角的新行为?