Let me share my experience from AEM 6.5 context.
Earlier I saw such type of error messages[not exactly the same] during minification in error.log file as Front End team kept saying JS minification wasn't working.
I did troubleshoot the issue and defined below steps -
1. AEM 6.5 uses following closure-compiler-v20190121.jar for js minification, also highlighted in below screenshot -
![DEBAL_DAS_0-1649081644576.png DEBAL_DAS_0-1649081644576.png](https://experienceleaguecommunities.adobe.com/t5/image/serverpage/image-id/39802i2074CA166BA99A88/image-size/medium/is-moderation-mode/true?v=v2&px=400)
2. If I take a closure look , I could see com.google.javascript is part of this closure compiler bundle.
3. Next I downloaded the bundle from aeminstance\crx-quickstart\launchpad\felix\bundle290. Bundle ID may vary in your case.
4. To understand the minification issue , I have executed below command to compile the Javascript file -
java -jar compiler.jar --js hello.js --js_output_file hello-compiled.js
[https://developers.google.com/closure/compiler/docs/gettingstarted_app]
It threw error during compilation. Then I requested Front End team to fix those issue so that minification works.
This steps will work with project specific client libraries[js files].
Even I faced issue with ECMASCRIPT versions also . I spoke to UI architect and he told me use latest ECMASCRIPT edition. [Please talk to your UI team lead or UI architect in details]