bc7f8ea433
zsh older than workers/28418 (zsh revision 23bdfc7fd2a012d5205ed22d18eb39e41c8fbc95) doesn't support the «${name:offset:length}» syntax. Therefore, use the older «$name[start,end]» syntax instead. Followup to 3cb58fd7d7b9e42067ffcf24892114dc2c9b26e4, "Optimization: -1 is extra computation of string length internally". Fixes zsh-users/zsh-syntax-highlighting#279.
zsh-syntax-highlighting / highlighters
Navigate into the individual highlighters' documentation to see
what styles ($ZSH_HIGHLIGHT_STYLES
keys) each highlighter defines.
Refer to the documentation on highlighters for further information.