Build optimization breaks my library code

[richardlnnr]

🐞 Bug report

Command (mark with an x)

- [ ] new
- [ x ] build
- [ x ] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Is this a regression?

Not sure.

Description

I created a workspace with two projects.

main-app is an application that is responsible for running the library.
domain is a library that has classes and utility methods.

When I build main-app in production (optimization=true), my utility function in domain library doesn't work.

Apparently, the problem only happens when you export arrow functions.

🔬 Minimal Reproduction

I created a repository in GitHub to reproduce this error.

🌍 Your Environment

Angular CLI: 7.3.2
Node: 10.15.1
OS: win32 x64
Angular: 7.2.6
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router

Package                            Version
------------------------------------------------------------
@angular-devkit/architect          0.13.2
@angular-devkit/build-angular      0.13.2
@angular-devkit/build-ng-packagr   0.13.2
@angular-devkit/build-optimizer    0.13.2
@angular-devkit/build-webpack      0.13.2
@angular-devkit/core               7.3.2
@angular-devkit/schematics         7.3.2
@angular/cli                       7.3.2
@ngtools/json-schema               1.1.0
@ngtools/webpack                   7.3.2
@schematics/angular                7.3.2
@schematics/update                 0.13.2
ng-packagr                         4.7.1
rxjs                               6.3.3
typescript                         3.2.4
webpack                            4.29.0

Anything else relevant?

[filipesilva]

Heya, can you elaborate on what doesn't work means in this context please? Does it return the wrong result, not run at all, or something else?

[richardlnnr]

When I export a function using arrow functions, apparently, the compiler ignores the code inside the function.

In the repository, I create the same code using the arrow function and a non-arrow function.
Just running the ng serve --prod is possible to see both functions called, and just remapWithoutArrowFunction working.

Those are the functions remand and remapWithoutArrowFunction

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