问在生产构建中获得‘Uncaught (in promise)：Error: StaticInjectorError(a)[t]:'....

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 import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { BsDatepickerModule } from 'ngx-bootstrap';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { HttpClientModule } from '@angular/common/http';
import { ChartsModule } from 'ng2-charts';

import { AppComponent } from './app.component';
import { HomeComponent } from './home/home.component';
import { MaterialModule } from './angular-material/material.module';
import { DashboardComponent } from './dashboard/dashboard.component';
import { AppRoutingModule } from './app.routing-module';
import { FiltersComponent } from './filters/filters.component';
import { SearchComponent } from './search/search.component';
import { ChartComponent } from './chart/chart.component';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { KeysPipe } from './shared/pipes/keys.pipe';
import { PdfViewerModule } from 'ng2-pdf-viewer';
import { AboutComponent } from './about/about.component';
@NgModule({
  declarations: [
    AppComponent,
    HomeComponent,
    DashboardComponent,
    FiltersComponent,
    SearchComponent,
    ChartComponent,
    KeysPipe,
    AboutComponent
  ],
  imports: [
    BrowserModule,
    BrowserAnimationsModule,
    FormsModule,
    ReactiveFormsModule,
    MaterialModule,
    ChartsModule,
    HttpClientModule,
    BsDatepickerModule.forRoot(),
    AppRoutingModule,
    PdfViewerModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

    Angular CLI: 6.0.8
Node: 10.2.1
OS: linux x64
Angular: 6.0.4
... animations, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

- 0.6.8, .6.8, .6.8, .6.8, -0.6.8, @angular/cdk -6.2.1, @angular/cli -6.0.8, @angular/material - 6.2.1, - 6.0.8, .6.8, - 0.6.8 , rxjs-6.2.1, typescript -2.7.2, webpack -4.8.3