title: error NG6002: Appears in the NgModule.imports of AppModule, but could not be resolved to an NgModule class
body: <p>First time using firestore and I'm getting this error. It seems to be a problem with Ivy, from my research. I don't have a lot of experience modifying tsconfig.app.json, which is the direction I've been pointed to, following other answers.</p>
  <p>The only thing I was able to modify from the original project was to use Angular Fire 6 instead of 5, which I had done initially to follow a tutorial.</p>
  <p>Here's package.json:</p>
  <pre class="lang-json prettyprint-override"><code>{
    &quot;name&quot;: &quot;language&quot;,
    &quot;version&quot;: &quot;0.0.0&quot;,
    &quot;scripts&quot;: {
      &quot;ng&quot;: &quot;ng&quot;,
      &quot;start&quot;: &quot;ng serve&quot;,
      &quot;build&quot;: &quot;ng build&quot;,
      &quot;test&quot;: &quot;ng test&quot;,
      &quot;lint&quot;: &quot;ng lint&quot;,
      &quot;e2e&quot;: &quot;ng e2e&quot;
    },
    &quot;private&quot;: true,
    &quot;dependencies&quot;: {
      &quot;@angular/animations&quot;: &quot;~9.0.1&quot;,
      &quot;@angular/cdk&quot;: &quot;^9.0.0&quot;,
      &quot;@angular/common&quot;: &quot;~9.0.1&quot;,
      &quot;@angular/compiler&quot;: &quot;~9.0.1&quot;,
      &quot;@angular/core&quot;: &quot;~9.0.1&quot;,
      &quot;@angular/fire&quot;: &quot;^6.0.0-rc.1&quot;,
      &quot;@angular/flex-layout&quot;: &quot;^9.0.0-beta.29&quot;,
      &quot;@angular/forms&quot;: &quot;~9.0.1&quot;,
      &quot;@angular/material&quot;: &quot;^9.0.0&quot;,
      &quot;@angular/platform-browser&quot;: &quot;~9.0.1&quot;,
      &quot;@angular/platform-browser-dynamic&quot;: &quot;~9.0.1&quot;,
      &quot;@angular/router&quot;: &quot;~9.0.1&quot;,
      &quot;firebase&quot;: &quot;^7.8.2&quot;,
      &quot;rxjs&quot;: &quot;~6.5.4&quot;,
      &quot;rxjs-compat&quot;: &quot;^6.5.4&quot;,
      &quot;tslib&quot;: &quot;^1.10.0&quot;,
      &quot;zone.js&quot;: &quot;~0.10.2&quot;
    },
    &quot;devDependencies&quot;: {
      &quot;@angular-devkit/build-angular&quot;: &quot;~0.900.2&quot;,
      &quot;@angular/cli&quot;: &quot;~9.0.2&quot;,
      &quot;@angular/compiler-cli&quot;: &quot;~9.0.1&quot;,
      &quot;@angular/language-service&quot;: &quot;~9.0.1&quot;,
      &quot;@types/node&quot;: &quot;^12.11.1&quot;,
      &quot;@types/jasmine&quot;: &quot;~3.3.8&quot;,
      &quot;@types/jasminewd2&quot;: &quot;~2.0.3&quot;,
      &quot;codelyzer&quot;: &quot;^5.1.2&quot;,
      &quot;jasmine-core&quot;: &quot;~3.4.0&quot;,
      &quot;jasmine-spec-reporter&quot;: &quot;~4.2.1&quot;,
      &quot;karma&quot;: &quot;~4.1.0&quot;,
      &quot;karma-chrome-launcher&quot;: &quot;~2.2.0&quot;,
      &quot;karma-coverage-istanbul-reporter&quot;: &quot;~2.0.1&quot;,
      &quot;karma-jasmine&quot;: &quot;~2.0.1&quot;,
      &quot;karma-jasmine-html-reporter&quot;: &quot;^1.4.0&quot;,
      &quot;protractor&quot;: &quot;~5.4.0&quot;,
      &quot;ts-node&quot;: &quot;~7.0.0&quot;,
      &quot;tslint&quot;: &quot;~5.15.0&quot;,
      &quot;typescript&quot;: &quot;~3.7.5&quot;,
      &quot;@angular-devkit/architect&quot;: &quot;^0.900.0-0 || ^0.900.0&quot;,
      &quot;firebase-tools&quot;: &quot;^7.12.1&quot;,
      &quot;fuzzy&quot;: &quot;^0.1.3&quot;,
      &quot;inquirer&quot;: &quot;^6.2.2&quot;,
      &quot;inquirer-autocomplete-prompt&quot;: &quot;^1.0.1&quot;
    }
  }
  </code></pre>
  <p>angular.json</p>
  <pre class="lang-json prettyprint-override"><code>{
    &quot;$schema&quot;: &quot;./node_modules/@angular/cli/lib/config/schema.json&quot;,
    &quot;version&quot;: 1,
    &quot;newProjectRoot&quot;: &quot;projects&quot;,
    &quot;projects&quot;: {
      &quot;language&quot;: {
        &quot;projectType&quot;: &quot;application&quot;,
        &quot;schematics&quot;: {
          &quot;@schematics/angular:component&quot;: {
            &quot;style&quot;: &quot;scss&quot;
          }
        },
        &quot;root&quot;: &quot;&quot;,
        &quot;sourceRoot&quot;: &quot;src&quot;,
        &quot;prefix&quot;: &quot;app&quot;,
        &quot;architect&quot;: {
          &quot;build&quot;: {
            &quot;builder&quot;: &quot;@angular-devkit/build-angular:browser&quot;,
            &quot;options&quot;: {
              &quot;outputPath&quot;: &quot;dist/language&quot;,
              &quot;index&quot;: &quot;src/index.html&quot;,
              &quot;main&quot;: &quot;src/main.ts&quot;,
              &quot;polyfills&quot;: &quot;src/polyfills.ts&quot;,
              &quot;tsConfig&quot;: &quot;tsconfig.app.json&quot;,
              &quot;aot&quot;: true,
              &quot;assets&quot;: [
                &quot;src/favicon.ico&quot;,
                &quot;src/assets&quot;
              ],
              &quot;styles&quot;: [
                &quot;./node_modules/@angular/material/prebuilt-themes/deeppurple-amber.css&quot;,
                &quot;src/styles.scss&quot;
              ],
              &quot;scripts&quot;: []
            },
            &quot;configurations&quot;: {
              &quot;production&quot;: {
                &quot;fileReplacements&quot;: [
                  {
                    &quot;replace&quot;: &quot;src/environments/environment.ts&quot;,
                    &quot;with&quot;: &quot;src/environments/environment.prod.ts&quot;
                  }
                ],
                &quot;optimization&quot;: true,
                &quot;outputHashing&quot;: &quot;all&quot;,
                &quot;sourceMap&quot;: false,
                &quot;extractCss&quot;: true,
                &quot;namedChunks&quot;: false,
                &quot;extractLicenses&quot;: true,
                &quot;vendorChunk&quot;: false,
                &quot;buildOptimizer&quot;: true,
                &quot;budgets&quot;: [
                  {
                    &quot;type&quot;: &quot;initial&quot;,
                    &quot;maximumWarning&quot;: &quot;2mb&quot;,
                    &quot;maximumError&quot;: &quot;5mb&quot;
                  },
                  {
                    &quot;type&quot;: &quot;anyComponentStyle&quot;,
                    &quot;maximumWarning&quot;: &quot;6kb&quot;,
                    &quot;maximumError&quot;: &quot;10kb&quot;
                  }
                ]
              }
            }
          },
          &quot;serve&quot;: {
            &quot;builder&quot;: &quot;@angular-devkit/build-angular:dev-server&quot;,
            &quot;options&quot;: {
              &quot;browserTarget&quot;: &quot;language:build&quot;
            },
            &quot;configurations&quot;: {
              &quot;production&quot;: {
                &quot;browserTarget&quot;: &quot;language:build:production&quot;
              }
            }
          },
          &quot;extract-i18n&quot;: {
            &quot;builder&quot;: &quot;@angular-devkit/build-angular:extract-i18n&quot;,
            &quot;options&quot;: {
              &quot;browserTarget&quot;: &quot;language:build&quot;
            }
          },
          &quot;test&quot;: {
            &quot;builder&quot;: &quot;@angular-devkit/build-angular:karma&quot;,
            &quot;options&quot;: {
              &quot;main&quot;: &quot;src/test.ts&quot;,
              &quot;polyfills&quot;: &quot;src/polyfills.ts&quot;,
              &quot;tsConfig&quot;: &quot;tsconfig.spec.json&quot;,
              &quot;karmaConfig&quot;: &quot;karma.conf.js&quot;,
              &quot;assets&quot;: [
                &quot;src/favicon.ico&quot;,
                &quot;src/assets&quot;
              ],
              &quot;styles&quot;: [
                &quot;./node_modules/@angular/material/prebuilt-themes/deeppurple-amber.css&quot;,
                &quot;src/styles.scss&quot;
              ],
              &quot;scripts&quot;: []
            }
          },
          &quot;lint&quot;: {
            &quot;builder&quot;: &quot;@angular-devkit/build-angular:tslint&quot;,
            &quot;options&quot;: {
              &quot;tsConfig&quot;: [
                &quot;tsconfig.app.json&quot;,
                &quot;tsconfig.spec.json&quot;,
                &quot;e2e/tsconfig.json&quot;
              ],
              &quot;exclude&quot;: [
                &quot;**/node_modules/**&quot;
              ]
            }
          },
          &quot;e2e&quot;: {
            &quot;builder&quot;: &quot;@angular-devkit/build-angular:protractor&quot;,
            &quot;options&quot;: {
              &quot;protractorConfig&quot;: &quot;e2e/protractor.conf.js&quot;,
              &quot;devServerTarget&quot;: &quot;language:serve&quot;
            },
            &quot;configurations&quot;: {
              &quot;production&quot;: {
                &quot;devServerTarget&quot;: &quot;language:serve:production&quot;
              }
            }
          },
          &quot;deploy&quot;: {
            &quot;builder&quot;: &quot;@angular/fire:deploy&quot;,
            &quot;options&quot;: {}
          }
        }
      }
    },
    &quot;defaultProject&quot;: &quot;language&quot;
  }
  </code></pre>
  <p>tsconfig.app.json</p>
  <pre class="lang-json prettyprint-override"><code>{
    &quot;extends&quot;: &quot;./tsconfig.json&quot;,
    &quot;compilerOptions&quot;: {
      &quot;outDir&quot;: &quot;./out-tsc/app&quot;,
      &quot;types&quot;: [],
    
    },
    &quot;files&quot;: [
      &quot;src/main.ts&quot;,
      &quot;src/polyfills.ts&quot;
    ],
    &quot;include&quot;: [
      &quot;src/**/*.d.ts&quot;
    ],
    &quot;exclude&quot;: [
      &quot;src/test.ts&quot;,
      &quot;src/**/*.spec.ts&quot;
    ]
  }
  </code></pre>
  <p>Thanks!</p>