There is a new pull request by fosslinux against master on the void-packages repository

https://github.com/fosslinux/void-packages swell-foop-vala
https://github.com/void-linux/void-packages/pull/25995

swell-foop: add patch fix build with latest vala.
Backported from upstream.

A patch file from https://github.com/void-linux/void-packages/pull/25995.patch is attached