xref-find-references show err message " Invalid slot type: xref-file-location, file, string, nil"

[tom]

when I use the global-tags.el . when I use xref-find-references, some symbol works well, but some symbol not. The error message is
eieio--validate-slot-value: Invalid slot type: xref-file-location, file, string, nil
But if I use counsel-gtags-find-reference, they all works well.

I try again after run toggle-debug-on-error. The stacktrace is (the attachmen is screenshot)

Debugger entered--Lisp error: (invalid-slot-type xref-file-location file string nil)
  signal(invalid-slot-type (xref-file-location file string nil))
  eieio--validate-slot-value(#s(eieio--class xref-file-location "A file location is a file/line/column triple.\nLine numbers start from 1 and columns from 0." (#s(eieio--class xref-location$
  eieio-oset(#<xref-file-location xref-file-location-1560a1e34f70> file nil)
  #f(compiled-function (obj slots) "Set slots of OBJ with SLOTS which is a list of name/value pairs.\nCalled from the constructor routine." #<bytecode 0x1560a0ccd889>)(#<xref-file-location $
  apply(#f(compiled-function (obj slots) "Set slots of OBJ with SLOTS which is a list of name/value pairs.\nCalled from the constructor routine." #<bytecode 0x1560a0ccd889>) #<xref-file-loc$
  shared-initialize(#<xref-file-location xref-file-location-1560a1e34f70> (:file nil :line nil :column nil))
  #f(compiled-function (this &optional slots) "Construct the new object THIS based on SLOTS.\nSLOTS is a tagged list where odd numbered elements are tags, and\neven numbered elements are th$
  apply(#f(compiled-function (this &optional slots) "Construct the new object THIS based on SLOTS.\nSLOTS is a tagged list where odd numbered elements are tags, and\neven numbered elements $
  initialize-instance(#<xref-file-location xref-file-location-1560a1e34f70> (:file nil :line nil :column nil))
  #f(compiled-function (class &rest slots) "Default constructor for CLASS `eieio-default-superclass'.\nSLOTS are the initialization slots used by `initialize-instance'.\nThis static method $
  apply(#f(compiled-function (class &rest slots) "Default constructor for CLASS `eieio-default-superclass'.\nSLOTS are the initialization slots used by `initialize-instance'.\nThis static m$
  make-instance(xref-file-location :file nil :line nil :column nil)
  xref-make-file-location(nil nil nil)
  (xref-make \.description (xref-make-file-location \.file \.line \.column))
  (let ((\.description (cdr (assq 'description alist))) (\.file (cdr (assq 'file alist))) (\.line (cdr (assq 'line alist))) (\.column (cdr (assq 'column alist)))) (xref-make \.description ($
  (let ((alist location-description)) (let ((\.description (cdr (assq 'description alist))) (\.file (cdr (assq 'file alist))) (\.line (cdr (assq 'line alist))) (\.column (cdr (assq 'column $
  global-tags--as-xref-location(nil)
  mapcar(global-tags--as-xref-location (nil))
  cl-mapcar(global-tags--as-xref-location (nil))
  global-tags--get-xref-locations(#("insert" 0 6 (face font-lock-function-name-face fontified t)) reference)
  (progn (global-tags--get-xref-locations symbol 'reference))
  (closure (t) (_backend symbol) (progn (global-tags--get-xref-locations symbol 'reference)))(global #("insert" 0 6 (face font-lock-function-name-face fontified t)))
  apply((closure (t) (_backend symbol) (progn (global-tags--get-xref-locations symbol 'reference))) global #("insert" 0 6 (face font-lock-function-name-face fontified t)))
  xref-backend-references(global #("insert" 0 6 (face font-lock-function-name-face fontified t)))
  #f(compiled-function () #<bytecode 0x1560a1e0746d>)()
  ivy-xref-show-xrefs(#f(compiled-function () #<bytecode 0x1560a1e0746d>) ((window . #<window 1 on parser.lua>) (display-action)))
  xref--show-xrefs(#f(compiled-function () #<bytecode 0x1560a1e0746d>) nil)
  xref--find-xrefs(#("insert" 0 6 (face font-lock-function-name-face fontified t)) references #("insert" 0 6 (face font-lock-function-name-face fontified t)) nil)
  xref-find-references(#("insert" 0 6 (face font-lock-function-name-face fontified t)))
  funcall-interactively(xref-find-references #("insert" 0 6 (face font-lock-function-name-face fontified t)))
  call-interactively(xref-find-references nil nil)
  command-execute(xref-find-references)

[tom (tpl-a1406)]

I add a test case. In the attach, when I run xref-find-references for symbol lpeg, the err can reappear.

[Felipe Lema (morenonatural)]

fixed @ https://git.launchpad.net/global-tags.el/commit/?id=818171d4b4af84e9a4c07a65fa6a985bd4ca8b2a

Thanks for the test case. That was really helpful to pinpoint the problem.