patch 8.2.1388: Vim9: += only works for numbers Commit: https://github.com/vim/vim/commit/dd29f1b0569cca253c80856eda2e85e04c1e0627 Author: Bram Moolenaar <Bram@vim.org> Date: Fri Aug 7 20:46:20 2020 +0200 patch 8.2.1388: Vim9: += only works for numbers Problem: Vim9: += only works for numbers. Solution: Use += as concatenate for a list. (closes https://github.com/vim/vim/issues/6646)