The static `ɵprov` field emitted on `@Injectable()` classes uses `ɵɵInjectableDeclaration<T>`.
When a subclass extends a generic `@Injectable()` base class with contravariant parameters
(such as callback/transformer methods depending on generic type parameters), TypeScript's
static side inheritance check (`typeof Sub extends typeof Super`) fails with `TS2417` because
`ɵɵInjectableDeclaration<Sub>` is not assignable to `ɵɵInjectableDeclaration<Super<any>>`.
Using `any` (`o.DYNAMIC_TYPE`) in `createInjectableType` avoids strict variance checks on
static inheritance for internal Ivy definitions and aligns with other Ivy declaration types.
These changes introduce the new `@Service` decorator which is a more ergonomic alternative to `@Injectable`. The reason we're adding a new decorator is that `@Injectable` has been around since the beginning of Angular and it has a lot of baggage that adds unnecessary overhead for users that generally want to define a singleton service, available in their entire app. The key differences between `@Service` and `@Injectable` are:
1. `@Service` is `providedIn: 'root'` by default. You can opt into providing the service yourself by setting `autoProvided: false` on it.
2. `@Service` doesn't allow constructor-based injection, only the `inject` function.
3. `@Service` doesn't support the complex type signature of `@Injectable` (`useClass`, `useValue` etc.). Instead it supports a single `factory` function.
Example:
```ts
import {Service} from '@angular/core';
import {HttpClient} from '@angular/common/http';
import {AuthService} from './auth';
@Service()
export class PostService {
private readonly httpClient = inject(HttpClient);
private readonly authService = inject(AuthService);
getUserPosts() {
return this.httpClient.get('/api/posts/' + this.authService.userId);
}
}
```
Andrew Scott