hideshow: Fix regressions. (Bug#79857)

* lisp/progmodes/hideshow.el (hs-block-positions): Exit the
function if 'hs-forward-sexp' fails.
(hs-hide-level-recursive): Fix infloop.
* test/lisp/progmodes/hideshow-tests.el (hideshow-hide-level-1):
(hideshow-hide-level-2): Update tests.

lisp/progmodes/hideshow.el

@@ -794,6 +794,9 @@ to call with the newly initialized overlay."
 This returns a list with the current code block beginning and end
 positions.  This does nothing if there is not a code block at current
 point."
+  ;; `catch' is used here if the search fails due unbalanced parentheses
+  ;; or any other unknown error caused in `hs-forward-sexp'.
+  (catch 'hs-sexp-error
     (save-match-data
       (save-excursion
         (when (funcall hs-looking-at-block-start-predicate)
@@ -807,7 +810,9 @@ point."
                 (goto-char (funcall hs-adjust-block-beginning-function header-end)))
               (setq block-beg (line-end-position)))
             ;; `block-end' is the point at the end of the block
+            (condition-case _
                 (hs-forward-sexp mdata 1)
+              (scan-error (throw 'hs-sexp-error nil)))
             (setq block-end
                   (cond ((and (stringp hs-block-end-regexp)
                               (looking-back hs-block-end-regexp nil))
@@ -821,7 +826,7 @@ point."
               (setq block-end
                     (or (funcall hs-adjust-block-end-function block-beg)
                         block-end)))
-          (list block-beg block-end))))))
+            (list block-beg block-end)))))))
 
 (defun hs--make-indicators-overlays (beg)
   "Helper function to make the indicators overlays."
@@ -1177,8 +1182,11 @@ region (point MAXP)."
 	    (not (nth 8 (syntax-ppss)))) ; not inside comments or strings
       (if (> arg 1)
 	  (hs-hide-level-recursive (1- arg) minp maxp)
-	(goto-char (match-beginning hs-block-start-mdata-select))
-	(hs-hide-block-at-point t))))
+        ;; `hs-hide-block-at-point' already moves the cursor, but if it
+        ;; fails, return to the previous position where we were.
+	(unless (and (goto-char (match-beginning hs-block-start-mdata-select))
+	             (hs-hide-block-at-point t))
+            (goto-char (match-end hs-block-start-mdata-select))))))
   (goto-char maxp))
 
 (defmacro hs-life-goes-on (&rest body)

test/lisp/progmodes/hideshow-tests.el

@@ -254,6 +254,8 @@ sub()
    Comments
 */
 
+\"String\"
+
 int
 main(int argc, char **argv)
 {
@@ -270,6 +272,8 @@ main(int argc, char **argv)
    Comments
 */
 
+\"String\"
+
 int
 main(int argc, char **argv)
 {}
@@ -284,6 +288,8 @@ main(int argc, char **argv)
    Comments
 */
 
+\"String\"
+
 int
 main(int argc, char **argv)
 {
@@ -300,6 +306,8 @@ main(int argc, char **argv)
    Comments
 */
 
+\"String\"
+
 int
 main(int argc, char **argv)
 {