Hi, in rollup 2.4.0 acorn-private-class-elements was added as a transitive dependency: v2.3.5...v2.4.0. That package uses the __proto__ property, but node recently added a --disable-proto option to disable its use due to security issues: nodejs/node#32279. Similarly, deno also recently removed support for __proto__: denoland/deno#4341.

I opened an issue with acorn-private-class-elements: acornjs/acorn-private-class-elements#13. I am opening an issue here as well because I saw that rollup is currently using forks of a couple acorn packages from @guybedford. Do you suggest waiting for the change to be made in acorn-private-class-elements or adding another fork?