production mode with es2015 breaks angular/common/http in angular-cli 6 beta 5

[benneq]

Versions

<!--
Angular CLI: 6.0.0-beta.5
Node: 9.7.1
OS: darwin x64
Angular: 6.0.0-beta.7
... animations, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

@angular/cdk: 6.0.0-beta.4
@angular/cli: 6.0.0-beta.5
@angular/flex-layout: 5.0.0-beta.13
@angular/material: 6.0.0-beta.4
@angular-devkit/build-optimizer: 0.4.5
@angular-devkit/core: 0.4.5
@angular-devkit/schematics: 0.4.5
@ngtools/json-schema: 1.2.0
@ngtools/webpack: 6.0.0-beta.5
@schematics/angular: 0.4.5
@schematics/package-update: 0.4.5
typescript: 2.6.2
webpack: 4.0.1

Repro steps

• Change tsconfig.json to es2015
• Use angular-cli production mode ( ng serve ---target=production --environment=prod )
• Use @angular/common/http
• Make HTTP request

Observed behavior

TypeError: Assignment to constant variable.

In this line:

o = ("responseURL"in (n = n) && n.responseURL ? n.responseURL : /^X-Request-URL:/m.test(n.getAllResponseHeaders()) ? n.getResponseHeader("X-Request-URL") : null) || t.url;

The problem is (n = n). Because n is defined as const n = this.xhrFactory.build();

Here are the corresponding lines in the angular source code:
o = ... = url = ...: https://github.com/angular/angular/blob/c8a1a14b87e5907458e8e87021e47f9796cb3257/packages/common/http/src/xhr.ts#L147
n = n: https://github.com/angular/angular/blob/c8a1a14b87e5907458e8e87021e47f9796cb3257/packages/common/http/src/xhr.ts#L25

Desired behavior

No error ;-)

Mention any other details that might be useful (optional)

It looks like the error comes from function inlining.

But I'm not sure if this problem is part of angular itself, or the TypeScript Compiler, or Uglify, or angular-cli because of bad default production settings.

[clydin]

Fixed via angular/devkit#519

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