that's only a transpiled version of it:
The Javascript version of the Closure-Compiler is
transpiled by GWT from the Java source. For more details
on the differences in behavior see the super sourced
files in the main repo.
Re:Closure Compiler vs Rollup vs Webpack
by fnordsensei on Monday April 10, 2017 @09:47AM
(#14078452)
Is that an issue?
No.
(But it's slower ;))
https://github.com/google/closure-compiler-js