Merge remote-tracking branch 'upstream/pr/433'

Note that there will be no zsh 5.3.2; zsh 5.3.1 will be followed
by 5.4.  There might be 5.4-test-1 pre-releases, though.

* upstream/pr/433:
  driver: Improve comment about ^r pattern match bug
  driver: Adjust zsh version for probing for pattern match bug
  README: Fix FAQ entry about isearch highlighting

README.md

@@ -46,23 +46,19 @@ syntax highlighting.
 
 ### Does syntax highlighting work during incremental history search?
 
-Yes!
+Highlighting the command line during an incremental history search (by default bound to
+to <kbd>Ctrl+R</kbd> in zsh's emacs keymap) requires zsh 5.4 or newer.
 
-If you're using `history-incremental-search-backward` (by default bound to <kbd>Ctrl+R</kbd>
-in zsh's emacs keymap) then it works with _zsh version 5.3 and newer_.
-
-If you're using `history-incremental-pattern-search-backward`, then syntax highlighting works
-in _zsh 5.3.2 and newer_ due to [a bug in zsh](http:https://www.zsh.org/cgi-bin/mla/redirect?WORKERNUMBER=40285).
-
-Under zsh 5.2 and older, the zsh-default [underlining][zshzle-Character-Highlighting]
+Under zsh versions older than 5.4, the zsh-default [underlining][zshzle-Character-Highlighting]
 of the matched portion of the buffer remains available, but zsh-syntax-highlighting's
 additional highlighting is unavailable. (Those versions of zsh do not provide
 enough information to allow computing the highlighting correctly.)
 
-See [issue #288][i288] for details.
+See issues [#288][i288] and [#415][i415] for details.
 
 [zshzle-Character-Highlighting]: http:https://zsh.sourceforge.net/Doc/Release/Zsh-Line-Editor.html#Character-Highlighting
 [i288]: https://github.com/zsh-users/zsh-syntax-highlighting/pull/288
+[i415]: https://github.com/zsh-users/zsh-syntax-highlighting/pull/415
 
 ### How are new releases announced?
 

zsh-syntax-highlighting.zsh

@@ -56,7 +56,7 @@ fi
 # Use workaround for bug in ZSH?
 # zsh-users/zsh@48cadf4 http:https://www.zsh.org/mla/workers//2017/msg00034.html
 autoload -U is-at-least
-if is-at-least 5.3.2; then
+if is-at-least 5.4; then
  zsh_highlight__pat_static_bug=false
 else
  zsh_highlight__pat_static_bug=true
@@ -77,7 +77,7 @@ _zsh_highlight()
  # Remove all highlighting in isearch, so that only the underlining done by zsh itself remains.
  # For details see FAQ entry 'Why does syntax highlighting not work while searching history?'.
  # This disables highlighting during isearch (for reasons explained in README.md) unless zsh is new enough
- # and doesn't have the 5.3.1 bug
+ # and doesn't have the pattern matching bug
  if [[ $WIDGET == zle-isearch-update ]] && { $zsh_highlight__pat_static_bug || ! (( $+ISEARCHMATCH_ACTIVE )) }; then
  region_highlight=()
  return $ret