anchor.diff:  (defun clear-diagnostic-overlays (buffer)
     (mapc #'delete-overlay (buffer-diagnostic-overlays buffer))
     (setf (buffer-diagnostic-overlays buffer) '()))
  +
  +(defun buffer-diagnostics (buffer)
  +  (mapcar (lambda (overlay)
  +            (overlay-get overlay 'diagnostic))
  +          (buffer-diagnostic-overlays buffer)))
  +
  +(defun point-to-xref-position (point)
  +  (lem.language-mode::make-xref-position :line-number (line-number-at-point point)
  +                                         :charpos (point-charpos point)))
   
   (defun highlight-diagnostic (buffer diagnostic)
     (with-point ((start (buffer-point buffer))
  
positive.code:     (protocol:diagnostic-severity.hint
       'diagnostic-hint-attribute)))
  
  (defun buffer-diagnostic-overlays (buffer)
    (buffer-value buffer 'diagnostic-overlays))
  
  
negative.code:                                        'diagnostic-error-attribute)
                                       (:no-error (severity)
                                         (diagnostic-severity-attribute severity))))))
          (overlay-put overlay
                       'diagnostic
                       (make-diagnostic :buffer buffer
                                        :position (point-to-xref-position start)
                                        :message (protocol:diagnostic-message diagnostic)))
          (push overlay (buffer-diagnostic-overlays buffer))))))
  
  (defun highlight-diagnostics (params)
  