Great post on #ClosureCompiler, it's history at #Google and how it evolved compared to #TypeScript.

https://effectivetypescript.com/2023/09/27/closure-compiler/

I can help with one of the last points:

> True to form, this tool [tsickle] is open source but pretty inscrutable to an outsider. It may be used by Angular but I couldn't tell.

I can confirm that Angular does *not* run `tsickle` or Closure in user projects with `ng build`. There was an experiment some years ago where we tried this to see if we could improve bundle sizes, but found that asking users to write Closure-optimizable code was too difficult and hard to justify outside Google. As a result, we never ran this in prod.

I believe we do technically run `tsickle` in Angular GitHub repositories, as we have a unique build system setup with #Bazel and #rules_nodejs. If you've ever contributed to Angular, you probably ran `tsickle`. We've been trying to remove this dependency, but I don't think it's happened yet.