driver: Use idiomatic module check

Author: phy1729

zsh-syntax-highlighting.zsh

@@ -51,12 +51,10 @@ fi
 
 # This function takes a single argument F and returns True iff F is an autoload stub.
 _zsh_highlight__function_is_autoload_stub_p() {
-  if (( ${+functions} )); then
-    ## zsh/parameter is available
+  if zmodload -e zsh/parameter; then
     #(( ${+functions[$1]} )) &&
     [[ "$functions[$1]" == *"builtin autoload -X" ]]
   else
-    ## zsh/parameter isn't available
     #[[ $(type -wa -- "$1") == *'function'* ]] &&
     [[ "${${(@f)"$(which -- "$1")"}[2]}" == $'\t'$histchars[3]' undefined' ]]
   fi
@@ -65,11 +63,9 @@ _zsh_highlight__function_is_autoload_stub_p() {
 
 # Return True iff the argument denotes a function name.
 _zsh_highlight__is_function_p() {
-  if (( ${+functions} )); then
-    ## zsh/parameter is available
+  if zmodload -e zsh/parameter; then
     (( ${+functions[$1]} ))
   else
-    ## zsh/parameter isn't available
     [[ $(type -wa -- "$1") == *'function'* ]]
   fi
 }