Call Screen debuted last year on the Pixel 3 and 3 XL, and has since expanded to the newer Pixel phones and a handful of other devices. If you're lucky enough to have this on your phone, you never have to answer another call without knowing who's on the other end. Google might be planning to automate part of the process, too. According to XDA, Call Screen may automatically screen select calls and hang up on spam.
On a phone with Call Screen, you currently have a button to activate the feature on an incoming call. However, an APK teardown reveals an as-yet unimplemented settings toggle that would allow the phone to screen calls from unknown numbers automatically. For spam and robocalls, the phone declines the call without pestering you. Any other unknown number will still ring through after screening.
Google added Call Screen transcripts some time ago, but automatic screening will bring with reportedly add the option to save recordings of screened calls. You'll also allegedly be able to customize what sorts of numbers trigger automatic screening. For example, hidden or potentially spoofed numbers. As with all unannounced Google features, there's no telling when (or even if) this feature will roll out.