Uncaught Error: Unexpected value 'PhotoDetailsModule' imported by the module 'PhotosModule'

// photo-details.component.ts
import { Component } from "@angular/core";
@Component({
    templateUrl: './photo-details.component.html',
})
export class PhotoDetailsComponent { }


// photo-details.module.ts
import { NgModule } from "@angular/core";
import { CommonModule } from "@angular/common";
import { PhotoDetailsComponent } from "./photo-details.component";
NgModule({
    declarations: [PhotoDetailsComponent],
    exports: [PhotoDetailsComponent],
    imports: [CommonModule]
})
export class PhotoDetailsModule { }


// photo-details.component.html
<h1>Oi</h1>


// photos.module.ts
import { CommonModule } from '@angular/common';
import { NgModule } from '@angular/core';
import { PhotoModule } from './photo/photo.module';
import { PhotoFormModule } from './photo-form/photo-form.module';
import { PhotoListModule } from './photo-list/photo-list.module';
import { PhotoDetailsModule } from './photo-details/photo-details.module';
@NgModule({
  imports: [
    CommonModule,
    PhotoModule,
    PhotoFormModule,
    PhotoListModule,
    PhotoDetailsModule]
})
export class PhotosModule { }

Quando eu adiciono PhotoDetailsModule à lista de imports de PhotosModule e salvo, recebo o seguinte erro na aplicação:

*compiler.js:1021 Uncaught Error: Unexpected value 'PhotoDetailsModule' imported by the module 'PhotosModule'. Please add a @NgModule annotation. *

No VS Code, em photo-details.component.ts, o nome do componente PhotoDetailsComponent aparece com o hint

Component 'PhotoDetailsComponent' is not included in a module and will not be available inside a template. Consider adding it to a NgModule declaration.

Não entendi a orientação, visto que ele está declarado em PhotoDetailsModule . Já reiniciei o Angular CLI e não fez diferença. O que estou fazendo de errado?