angular-cli: [6.0.0 Regression] build-optimizer breaks exports

Versions

     _                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
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Angular CLI: 6.0.0
Node: 9.11.1
OS: darwin x64
Angular: 6.0.0
... animations, cli, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.6.0
@angular-devkit/build-angular     0.6.0
@angular-devkit/build-optimizer   0.6.0
@angular-devkit/core              0.6.0
@angular-devkit/schematics        0.6.0
@ngtools/webpack                  6.0.0
@schematics/angular               0.6.0
@schematics/update                0.6.0
rxjs                              6.1.0
typescript                        2.7.2
webpack                           4.6.0

Repro steps

• git clone https://github.com/buu700/ng6-quill-test.git
• cd ng6-quill-test
• npm install .
• ng serve --prod

This project is a small modification of ng new’s output which adds import 'parchment';. The relevant code within the parchment package is as follows:

src/registry.ts:

. . .
export enum Scope {
  . . .
  INLINE_BLOT = INLINE & BLOT, // 0110
  . . .
}
. . .


src/blob/abstract/leaf.ts:

. . .
import * as Registry from '../../registry';

class LeafBlot extends ShadowBlot implements Leaf {
  static scope = Registry.Scope.INLINE_BLOT;
. . .

Observed behavior

Logged to console:

Uncaught TypeError: Cannot read property 'INLINE_BLOT' of undefined

Desired behavior

As when building/serving without --prod, Registry.Scope should be defined.

Mention any other details that might be useful (optional)

Disabling the build optimizer fixes the issue. I didn’t run into this with 6.0.0-rc.7, so the regression is from some time between 6.0.0-rc.8 and 6.0.0 final.