'Observable' is not a class derived from 'Observable'

Question

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

Answer 1

I was getting a crazy error like

Type 'Observable' cannot be converted to type 'Observable'
Property 'source' is protected but type 'Observable' is not a class derived from 'Observable'

And the reason was npm link (actually npm i ../other-project but it's quite the same thing).

My workaround was kinda cheating:

(stream as any as Observable)

LOL