Fix compatibility with latest zsh-syntax-highlighting

zsh-syntax-highlighting started using zle-line-pre-redraw hook instead
of the legacy "bind all widgets" if 1) zsh has the memo= feature (added
in version 5.9) and 2) add-zle-hook-widget is available.

Now when zsh-history-substring-search is loaded before
zsh-syntax-highlighting, it causes error:

    _zsh_highlight_widget_zle-line-pre-redraw: job table full or recursion limit exceeded

See https://github.com/zsh-users/zsh-syntax-highlighting/pull/749

zsh-history-substring-search.zsh

@@ -106,6 +106,8 @@ zmodload -F zsh/parameter
 # https://github.com/nicoulaj/zsh-syntax-highlighting
 #
 if [[ $+functions[_zsh_highlight] -eq 0 ]]; then
+  autoload -U is-at-least
+
   #
   # Dummy implementation of _zsh_highlight() that
   # simply removes any existing highlights when the
@@ -117,6 +119,75 @@ if [[ $+functions[_zsh_highlight] -eq 0 ]]; then
     fi
   }
 
+  #
+  # Check if $1 denotes the name of a callable function, i.e. it is fully
+  # defined or it is marked for autoloading and autoloading it at the first
+  # call to it will succeed. In particular, if $1 has been marked for
+  # autoloading but is not available in $fpath, then it will return 1 (false).
+  #
+  # This is based on the zsh-syntax-highlighting plugin.
+  #
+  _history-substring-search-function-callable() {
+    if (( ${+functions[$1]} )) && ! [[ "$functions[$1]" == *"builtin autoload -X"* ]]; then
+      return 0 # already fully loaded
+    else
+      # "$1" is either an autoload stub, or not a function at all.
+      # We expect 'autoload +X' to return non-zero if it fails to fully load
+      # the function.
+      ( autoload -U +X -- "$1" 2>/dev/null )
+      return $?
+    fi
+  }
+
+  #
+  # The zsh-syntax-highlighting plugin uses zle-line-pre-redraw hook instead
+  # of the legacy "bind all widgets" if 1) zsh has the memo= feature (added in
+  # version 5.9) and 2) add-zle-hook-widget is available.
+  #
+  if is-at-least 5.9 $ZSH_VERSION && _history-substring-search-function-callable add-zle-hook-widget; then
+    #
+    # The following code is based on the zsh-syntax-highlighting plugin.
+    #
+    autoload -U add-zle-hook-widget
+
+    _history-substring-search-zle-line-finish() {
+      #
+      # Reset $WIDGET since the 'main' highlighter depends on it.
+      #
+      # Since $WIDGET is declared by zle as read-only in this function's scope,
+      # a nested function is required in order to shadow its built-in value;
+      # see "User-defined widgets" in zshall.
+      #
+      () {
+        local -h -r WIDGET=zle-line-finish
+        _zsh_highlight
+      }
+    }
+
+    _history-substring-search-zle-line-pre-redraw() {
+      #
+      # If the zsh-syntax-highlighting plugin has been loaded (after our plugin
+      # plugin, otherwise this hook wouldn't be called), remove our hooks.
+      #
+      if [[ $+ZSH_HIGHLIGHT_VERSION -eq 1 ]]; then
+        autoload -U add-zle-hook-widget
+        add-zle-hook-widget -d zle-line-pre-redraw _history-substring-search-zle-line-pre-redraw
+        add-zle-hook-widget -d zle-line-finish _history-substring-search-zle-line-finish
+        return 0
+      fi
+      #
+      # Set $? to 0 for _zsh_highlight.  Without this, subsequent
+      # zle-line-pre-redraw hooks won't run, since add-zle-hook-widget happens to
+      # call us with $? == 1 in the common case.
+      #
+      true && _zsh_highlight "$@"
+    }
+
+    if [[ -o zle ]]; then
+      add-zle-hook-widget zle-line-pre-redraw _history-substring-search-zle-line-pre-redraw
+      add-zle-hook-widget zle-line-finish _history-substring-search-zle-line-finish
+    fi
+  else
     #
     # The following snippet was taken from the zsh-syntax-highlighting project:
     # https://github.com/zsh-users/zsh-syntax-highlighting/blob/56b134f5d62ae3d4e66c7f52bd0cc2595f9b305b/zsh-syntax-highlighting.zsh#L126-161
@@ -167,6 +238,9 @@ if [[ $+functions[_zsh_highlight] -eq 0 ]]; then
     _zsh_highlight_bind_widgets
   fi
 
+  unfunction _history-substring-search-function-callable
+fi
+
 _history-substring-search-begin() {
   setopt localoptions extendedglob