第一次使用 firestore 时出现此错误。根据我的研究，这似乎是 Ivy 的问题。我没有很多修改 tsconfig.app.json 的经验，这是我被指出的方向，遵循其他答案。
我能够从原始项目中修改的唯一一件事是使用 Angular Fire 6 而不是 5，这是我最初按照教程所做的。
这是 package.json：
{
"name": "language",
"version": "0.0.0",
"scripts": {
"ng": "ng",
"start": "ng serve",
"build": "ng build",
"test": "ng test",
"lint": "ng lint",
"e2e": "ng e2e"
},
"private": true,
"dependencies": {
"@angular/animations": "~9.0.1",
"@angular/cdk": "^9.0.0",
"@angular/common": "~9.0.1",
"@angular/compiler": "~9.0.1",
"@angular/core": "~9.0.1",
"@angular/fire": "^6.0.0-rc.1",
"@angular/flex-layout": "^9.0.0-beta.29",
"@angular/forms": "~9.0.1",
"@angular/material": "^9.0.0",
"@angular/platform-browser": "~9.0.1",
"@angular/platform-browser-dynamic": "~9.0.1",
"@angular/router": "~9.0.1",
"firebase": "^7.8.2",
"rxjs": "~6.5.4",
"rxjs-compat": "^6.5.4",
"tslib": "^1.10.0",
"zone.js": "~0.10.2"
},
"devDependencies": …