Fixing "Unknown slot" warnings

Fixing "Unknown slot" warnings

[David Engster]

I'm currently fixing the above byte-compiler warnings for CEDET. I've
replaced all the 'oref' with 'slot-value' and properly used quotes for
the slot names, but there are some warnings remaining. The reason is
that the byte-compiler has not seen the class declaration, so it does
not know about the available slots. However, I cannot simply
eval-when-compile-require the file with the class as it would create a
circular dependency.

Example: Compiling lisp/cedet/semantic.el issues

  In semantic-analyze-completion-at-point-function:
  cedet/semantic.el:1188:15:Warning: Unknown slot ‘bounds’

The class declaration for `semantic-analyze-context' is in
semantic/analyze.el, which however itself requires semantic.

How can I tell the compiler everything will be OK at runtime, similar to
what 'declare-function' does for functions?

-David

Re: Fixing "Unknown slot" warnings

[Stefan Monnier]

> How can I tell the compiler everything will be OK at runtime, similar to
> what 'declare-function' does for functions?

I don't think we have something for that right now.
Maybe you can try something like:

    (eval-when-compile (defclass dummy () ((SLOT))))

Better would be to wrap this into an `eieio-declare-slot` macro (which
could later be replaced by something which doesn't end up defining
a class as a side-effect).


        Stefan

Re: Fixing "Unknown slot" warnings

[David Engster]

Stefan Monnier writes:
>> How can I tell the compiler everything will be OK at runtime, similar to
>> what 'declare-function' does for functions?
>
> I don't think we have something for that right now.
> Maybe you can try something like:
>
>     (eval-when-compile (defclass dummy () ((SLOT))))
>
> Better would be to wrap this into an `eieio-declare-slot` macro (which
> could later be replaced by something which doesn't end up defining
> a class as a side-effect).

After looking at the code, it seems all slot symbols are shoved into
`eieio--known-slot-names' and the byte-compiler checks if a slot is in
there, regardless of the class being used. So the following would
already do the trick:

(defmacro eieio-declare-slot (name)
  "Declares slot to be available at runtime."
  `(eval-when-compile (cl-pushnew ,name eieio--known-slot-names)))

-David

Re: Fixing "Unknown slot" warnings

[Stefan Monnier]

> After looking at the code, it seems all slot symbols are shoved into
> `eieio--known-slot-names' and the byte-compiler checks if a slot is in
> there, regardless of the class being used. So the following would
> already do the trick:

> (defmacro eieio-declare-slot (name)
>   "Declares slot to be available at runtime."
>   `(eval-when-compile (cl-pushnew ,name eieio--known-slot-names)))

If you mean something to add to eieio, then yes, that's about right
(tho you could also do it as (defmacro eieio-declare-slot (name)
(cl-pushnew name eieio--known-slot-names) nil).

My `defclass` solution was meant for use in code that must work with
older Emacsen and/or older eieio without relying on internals like 
eieio--known-slot-names.


        Stefan

Re: Fixing "Unknown slot" warnings

[David Engster]

Stefan Monnier writes:
>> After looking at the code, it seems all slot symbols are shoved into
>> `eieio--known-slot-names' and the byte-compiler checks if a slot is in
>> there, regardless of the class being used. So the following would
>> already do the trick:
>
>> (defmacro eieio-declare-slot (name)
>>   "Declares slot to be available at runtime."
>>   `(eval-when-compile (cl-pushnew ,name eieio--known-slot-names)))
>
> If you mean something to add to eieio, then yes, that's about right
> (tho you could also do it as (defmacro eieio-declare-slot (name)
> (cl-pushnew name eieio--known-slot-names) nil).

OK, I'll add that to EIEIO.

> My `defclass` solution was meant for use in code that must work with
> older Emacsen and/or older eieio without relying on internals like 
> eieio--known-slot-names.

The new CEDET will only target the current master, so I finally don't
have to care about older Emacsen anymore.

-David