Angular 2启动报错：执行npm start时出现TS2415类型兼容错误

Hey there! I’ve seen this exact error a bunch of times with older Angular 2 setups—it’s all about version conflicts between TypeScript and RxJS. Let’s get you back on track with your Udemy course:

What’s Causing This? #

The error Class 'Subject<T>' incorrectly extends base class 'Observable<T>' pops up because TypeScript 2.4+ introduced stricter generic type checking. The RxJS version used in Angular 2 (RxJS 5.x) has a lift method in Subject that doesn’t match the signature TypeScript now expects, leading to this type mismatch.

How to Fix It #

Follow these steps to resolve the conflict:

1. Adjust Your TypeScript Version
   Your current TypeScript version is likely too new for the RxJS version in your Angular 2 project. Open your package.json and update the typescript entry in devDependencies to use a compatible version:

   "devDependencies": {
     // ... keep other dependencies as-is
     "typescript": "~2.3.4"
   }
   

   This version works perfectly with Angular 2 and RxJS 5.x without type checking issues.

2. Clean Up Dependencies
   To make sure there are no leftover conflicting files, delete your node_modules folder and clear the npm cache:

   rm -rf node_modules
   npm cache clean --force
   

   Then reinstall all dependencies:

   npm install
   

3. Verify the Fix
   Run your start command again:

   npm start
   

   This should resolve the type error and let your app compile and run as expected.

Double-Check Your tsconfig.json #

If you still run into issues, make sure your tsconfig.json has the correct compiler settings for Angular 2. Here’s a working configuration you can use:

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "sourceMap": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "lib": ["es2015", "dom"],
    "noImplicitAny": true,
    "suppressImplicitAnyIndexErrors": true
  },
  "exclude": [
    "node_modules"
  ]
}

That should get you past this error so you can keep building those 12 apps in your course!

内容的提问来源于stack exchange，提问作者john