Gnu ELPA cl-generic bug?

Gnu ELPA cl-generic bug?

[Stephen Leake]

I'm trying to use the Gnu ELPA package cl-generic to support
cl-defmethod in Emacs 24.5.

I have this set of definitions:

(cl-defstruct wisi-parser
  ;; Separate lists for lexer and parse errors, because lexer errors
  ;; must be repaired first, before parse errors can be repaired. And
  ;; they have different structures.
  lexer-errors
  ;; list of wisi--lexer-errors from last parse.  Can be more than one if
  ;; lexer supports error recovery.
  parse-errors
  ;; List of wisi--parse-errors from last parse. Can be more than one if
  ;; parser supports error recovery.
)

(cl-defgeneric wisi-parse-kill ((parser wisi-parser))
  "Kill any external process associated with parser.")


(cl-defstruct (wisi-elisp-parser (:include wisi-parser))
  actions
  gotos
  next-token
  )

(cl-defmethod wisi-parse-kill ((_parser wisi-elisp-parser))
  nil)


(cl-defstruct (wisi-process--parser (:include wisi-parser))
 ...
 )
 
(cl-defmethod wisi-parse-kill ((parser wisi-process--parser))
  (when (process-live-p (wisi-process--parser-process parser))
    (process-send-string (wisi-process--parser-process parser) wisi-process-parse-quit-cmd)
    (sit-for 1.0)
    (when (process-live-p (wisi-process--parser-process parser))
      (kill-process (wisi-process--parser-process parser)))
    )
  (setf (wisi-process--parser-busy parser) nil))


Whenever one of these 'cl-defmethod' forms is encountered, the byte
compiler issues an error:

Error: Unknown class type wisi-elisp-parser in method parameters

The ELPA package cl-generic defines cl-defgeneric and cl-defmethod,
using eieio defgeneric and defmethod. It does _not_ define cl-defstuct;
that has its normal definition that does not use eieio.

So I suspect the problem is that the eieio class 'wisi-elisp-parser' is
never declared, because 'cl-defstruct' does not call eieio defclass.

Is there a simple fix for this?

-- 
-- Stephe

Re: Gnu ELPA cl-generic bug?

[Stefan Monnier]

> I'm trying to use the Gnu ELPA package cl-generic to support
> cl-defmethod in Emacs 24.5.
[...]
> (cl-defstruct wisi-parser
[...]
> (cl-defgeneric wisi-parse-kill ((parser wisi-parser))

That won't work: the GNU ELPA package only provides the common subset
between the old EIEIO defmethod and the cl-generic cl-defmethod.
More specifically, you can only dispatch on the first arg and only on
EIEIO classes, not defstructs, nor built-in types.

IOW, it only lets you use the cl-generic syntax instead of the old EIEIO
syntax.


        Stefan