patch 8.0.0655: not easy to make sure a function does not exist commit https://github.com/vim/vim/commit/d6abcd154cdc6a8dd4b7c6ccad37617ea8a1b4aa Author: Bram Moolenaar <Bram@vim.org> Date: Thu Jun 22 19:15:24 2017 +0200 patch 8.0.0655: not easy to make sure a function does not exist Problem: Not easy to make sure a function does not exist. Solution: Add ! as an optional argument to :delfunc.

" Vim syntax file
" Language:  systemd.unit(5)

if !exists('b:current_syntax')
  " Looks a lot like dosini files.
  runtime! syntax/dosini.vim
  let b:current_syntax = 'systemd'
endif