Angular8 firebase configuration error '@angular/fire/angularfire2'

This error is due to TypeScript type checking the definitions file of the AngularFire library.

Notice the errors are from node_modules/@angular/fire/angularfire2.d.ts:37:49.

To avoid this error you have to set some options in tsconfig.json.

tsconfig:

{
  //...
  compilerOptions: {
    "skipLibCheck": true,
    //...
  }
}

skipLibCheck: Skip type checking of declaration files.

More info on the skipLibCheck option.