`signatureHelp`: False expression: Not a subspan

[elibarzilay]

See microsoft/tsserverfuzzer#309

/**
 * @typedef {Object} Foo
 * @property {number} ...

 * @typedef {Object} Bar
 * @property {number} ...
 */

/*

(defun z ()
  (interactive)
  (with-temp-file "tsconfig.json" (insert "{}"))
  (setq-local tide-tsserver-process-environment
              '("TSS_LOG=-level verbose -file /tmp/t.log"))
  (tide-restart-server)
  (tide-send-command-sync
   "signatureHelp"
   `(:file ,buffer-file-name
     :position ,(1- (save-excursion
                      (goto-char (point-min))
                      (re-search-forward "@type.*Bar")
                      (match-beginning 0)))))
  (delete-file "tsconfig.json")
  (tide-kill-server))

*/