ES2015 + emitDecoratorMetadata causes Cannot access before intialization

[pauldraper]

🐞 bug report

Affected Package

@angular/compiler

Is this a regression?

No, but this is more relevant now because angular-cli permits ES2015 targets.

Description

When targeting ES2015, emitDecoratorMetadata causes a ReferenceError.

🔬 Minimal Reproduction

https://github.com/pauldraper/angular-decorator-metadata

ng serve

Load in browser.

🔥 Exception or Error

main.js:98 Uncaught ReferenceError: Cannot access 'AppService' before initialization
    at Module../src/app.component.ts (main.js:98)
    at __webpack_require__ (runtime.js:80)
    at Module../src/app.module.ts (main.js:123)
    at __webpack_require__ (runtime.js:80)
    at Module../src/main.ts (main.js:157)
    at __webpack_require__ (runtime.js:80)
    at Object.0 (main.js:174)
    at __webpack_require__ (runtime.js:80)
    at checkDeferredModules (runtime.js:46)
    at Array.webpackJsonpCallback [as push] (runtime.js:33)

🌍 Your Environment

Angular Version:

Angular 8.1.1

Anything else relevant?

Removing emitDecoratorMetadata, or targeting es5 fixes the problem.

[alan-agius4]

Hi, is there a reason why you need emitDecoratorMetadata to be true?

By the way @pauldraper, love your repo.

[clydin]

This TypeScript option has a fundamental design limitation with ES2015+ code and is best avoided when targeting such output. As such this is an issue with TypeScript itself and not Angular.

Angular 8+ no longer requires the option. It was also previously only required for JIT mode which is typically only used in development.

[piotrpalek]

Maybe it would be good to check for that when upgrading angular, or mention it in the docs? This just took me quiet a bit to figure out after upgrading from angular 7 -> 8

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