Angular 6 & RxJS 6 Breaking Changes

Look more closely at the error message. It says that

import("c:/ProjDotNet/collegebowl-site/node_modules/@angular/core/node_modules/rxjs/internal/Observable").Observable>

and

import("c:/ProjDotNet/collegebowl-site/node_modules/rxjs/internal/Observable").Observable>

are different types. That is, you actually have two different kinds of Observable that come from separate copies of RxJS that reside in different directories in your file system.

That is, your node_modules is in a very weird state. Running npm ls rxjs or yarn why rxjs might yield clues as to why npm / yarn thought it a good idea to install RxJS twice.

Like @meriton said, this is because you have multiple instance of rxjs in multiple node_modules. The best solution I've found is to add an alias into tsconfig.json to force the use of the same rxjs everywhere :

"compilerOptions": {
  "paths": {
      "rxjs": [
        "node_modules/rxjs"
      ],
      "rxjs/*": [
        "node_modules/rxjs/*"
      ]
   }
}