'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

actually may this problem comes due to your typescript version change

try to change your typescript version

1. You can find that in

   package.json

set to 2.4.3

2. if not work then simply try on cli

   npm unlink typescript

   npm install typescript@2.3.4

and after installation complete packages.json

plz check it should be work in dependencies

"dependencies": {
"@angular/animations": "^5.2.0",
"@angular/common": "^5.2.0",
"@angular/compiler": "^5.2.0",
"@angular/core": "^5.2.0",
"@angular/forms": "^5.2.0",
"@angular/http": "^5.2.0",
"@angular/platform-browser": "^5.2.0",
"@angular/platform-browser-dynamic": "^5.2.0",
"@angular/router": "^5.2.0",
"core-js": "^2.4.1",
"rxjs": "5.4.3",
"typescript": "^2.3.4", <<---------------remove ^
"zone.js": "^0.8.19"

but one thing is clear it is not error this is due to environment change

if still facing problem then try reinstall node module

good luck.......