'Observable<T>' is not a class derived from 'Observable<T>'
rxjs5, typescript
Solution
I just came across a very similar issue while developing a custom module for a project. I'm not 100% sure we were having the same problem, but it looks pretty close.
How I resolved my problem
I would suggest deleting your `node_modules` folder and reinstalling all your dependencies.
rm -rf node_modules/
npm cache clean
npm install
That solved it for me.
What the problem was (I think)
The module I was developing had an abstract class that the main project was trying to extend. However when trying to compile the main project, the compiler would throw the same error you are getting.
After a bit of digging around, I noticed NPM would complain about an `UNMET PEER DEPENDENCY` when installing my module into my project. When looking inside the `node_modules` of the project, I noticed that my module had another `node_modules` folder nested inside of it with some dependencies that it shared with the main project.
I'm not certain about this, but I think NPM thought the module was expecting different version of dependencies it shared with the main project.
So the abstract class inside the module was referencing Observable from its own nested `node_modules` folder while the main project was referencing Observable from the top level `node_modules` folder.
More information
This other questions provided some insight for me when trying solve my problem:
Why does npm install say I have unmet dependencies?
Problem
When trying to extend a class from a class in a `node_modules` the typescript compiler throws a error saying: `Property 'source' is protected but type 'Observable<T>' is not a class derived from 'Observable<T>'.` This only happens when the base class is from a `node_module`. The base class looks like: ``` import {Observable} from "rxjs/Observable"; export abstract class TestBase<T> { request(options: any):Observable<T> { return Observable.throw(new Error('TestBase is abstract class. Extend it and implement own request method')); } } ``` Subclassing it in a project: ``` import {Observable} from "rxjs/Observable"; import {TestBase} from "@org/core"; class SocketResponse { } class Socket { request(): Observable<SocketResponse> { return new Observable.of(new SocketResponse()); } } export class Sub extends TestBase<SocketResponse> { request(options:any):Observable<SocketResponse> { return new Socket().request(); } } ``` If the base class (`TestBase`) is moved from the `node_module` to the project it self and change the import to look like `import {TestBase} from "./base";` The error disappears. Is this due to that the compiles creates the types in different scopes for each module? I'm completely lost here. Update: This seems to only happen when linking the `node_modules` with `npm link`. Seems like one possible workaround for the moment is to instead of returning a type in the base class to return a interface. More information can be found here: https://github.com/Microsoft/TypeScript/issues/6496 https://github.com/ReactiveX/rxjs/issues/1744