Big Bundle size - Tree shaking not working for operators

Bug Report

Current Behavior When creating a minimal project using rxjs the bundle size for that project is very heavy even when using just one or two operators (+600Kb uncompressed)

Reproduction

• Here I show you a minimal repo where I am just using ONE operator (map operator) and the bundle size is big: https://github.com/sandinosaso/rxjs-big-bundle-bug

import { Observable } from 'rxjs/internal/Observable';
import { map } from 'rxjs/operators';
let x = Observable.create();
x.pipe(
  map((v) => v++)
)

Expected behavior I expect the bundle size to be only related to the number of operators I import in this case should be 7.5 Kb and not 577 Kb

Environment

• Runtime: [e.g. Node v${x}, Chrome v${x}]
• RxJS version: 6.5.2
• Webpack 4.32.2

Possible Solution Not sure I thought by the docs that tree shaking should work out of the box for this project. Not sure how to help with this.

Additional context/Screenshots Before importing operators the bundle size is ( ** 36.8 Kb ** ):

After import just map operator the bundle size is ( ** 577 Kb ** ):

[cartant]

https://github.com/ReactiveX/rxjs/blob/master/docs_app/content/guide/v6/migration.md#import-paths

[cartant]

You should NOT be importing from internal locations. Your screen shots indicate you are importing from rxjs/internal/Observable, etc. Your doing so is not supported.