rxjs/Subject.d.ts error : Class 'Subject' incorrectly extends base class 'Observable'

Question

I extracted sample template code from this tutorial and did below two steps to get started -

1. npm install // worked fine and created node_modules folder

Answer 1

RxJS 6 will have this fixed, but as a temporary workaround, you can use the noStrictGenericChecks compiler option.

In tsconfig.json, put it in compilerOptions and set it to true.

{
    "compilerOptions": {
        "noStrictGenericChecks": true
    }
}

On the command line it's --noStrictGenericChecks.

Why it's happening:

TypeScript 2.4 has a strictness change, and Subject isn't lifting to the correct Observable. The signature really should have been

(operator: Operator) => Observable

This will be fixed in RxJS 6.