Why must zsh-syntax-highlighting.zsh be sourced at the end of the .zshrc file?
zsh-syntax-highlighting works by hooking into the Zsh Line Editor (ZLE) and computing syntax highlighting for the command-line buffer as it stands at the time z-sy-h's hook is invoked.
In zsh 5.2 and older, zsh-syntax-highlighting.zsh hooks into ZLE by wrapping ZLE widgets. It must be sourced after all custom widgets have been created (i.e., after all zle -N calls and after running compinit) in order to be able to wrap all of them. Widgets created after z-sy-h is sourced will work, but will not update the syntax highlighting.
In zsh newer than 5.8 (not including 5.8 itself), zsh-syntax-highlighting uses the add-zle-hook-widget facility to install a zle-line-pre-redraw hook. Hooks are run in order of registration, therefore, z-sy-h must be sourced (and register its hook) after anything else that adds hooks that modify the command-line buffer.
根据zsh-syntax-highlighting 的github主页
在高于5.8版本的zsh中，
zsh-syntax-highlighting.zsh需要在文件的末尾被引用才能正确的注册hook并生效