patch 8.2.4240: error for using flatten() in Vim9 script is unclear Commit: https://github.com/vim/vim/commit/fb80862e49fcbcf47907fc8cdaaf5c41cb9eb06e Author: Bram Moolenaar <Bram@vim.org> Date: Fri Jan 28 15:01:47 2022 +0000 patch 8.2.4240: error for using flatten() in Vim9 script is unclear Problem: Error for using flatten() in Vim9 script is unclear. Solution: Add a remark to use flattennew().