I recently got a private report about a problem with the new lisp indent
functions: they don't work well when the buffer contains syntax errors.
For example, indent-region in a buffer containing:

)
(+ 2
   3)

gives

Debugger entered--Lisp error: (wrong-type-argument consp nil)
  lisp-indent-calc-next(#s(lisp-indent-state :stack (nil) :ppss (0 nil nil nil nil nil 0 nil nil nil nil) :ppss-point 146))
  lisp-indent-region(146 158)
  indent-region(146 158 nil)
  funcall-interactively(indent-region 146 158 nil)
  call-interactively(indent-region nil nil)
  command-execute(indent-region)

The error can be fixed with the patch below, I think it's safe for
emacs-26.  But, it still gives wrong indentation if you do indent-region
on the latter two lines.  That could be fixed with

    (advice-add 'lisp-ppss :override
                #'lisp-ppss-open-paren-in-column-0-is-defun-start)

The lisp-ppss-open-paren-in-column-0-is-defun-start function is included
(but uncalled) in the patch.  Using it in the override suggested above
will bring back Bug#27920 though.  We could include the function and
suggest to use it (with the aforementioned caveat) in etc/NEWS or
PROBLEMS perhaps?