Advice functions: required args that byte-compiler warns are unused

Advice functions: required args that byte-compiler warns are unused

[Drew Adams]

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I'm wondering how you deal with this - what's a
good way.

I have an advice function `my-foo-after-advice',
which I use as an :after advice for function `foo':

 (defun my-foo-after-advice (&rest args)
   "..."
   (ignore args)      ; Quiet the byte-compiler.
   (do-stuff-that-doesnt-refer-to-ARGS))

Suppose function `foo' requires 3 arguments:

 (defun foo (a b c) ...)

An :after advice needs to accept the same args as
the function it advises.  But the byte-compiler
warns "Unused lexical argument 'args'" (naturally).

So I've been adding an `(ignore args)'.

Is there a better way to suppress such a warning?
I looked for a `declare' possibility for this,
which would be a declaration to the byte-compiler
rather than a runtime operation.

Of course `ignore' doesn't cost much here, but it
seems like we should be able to keep info for the
compiler separate from code that gets run.

Hope I'm missing something simple.

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Re: Advice functions: required args that byte-compiler warns are unused

[Stefan Monnier via Users list for the GNU Emacs text editor]

>  (defun my-foo-after-advice (&rest args)
>    "..."
>    (ignore args)      ; Quiet the byte-compiler.
>    (do-stuff-that-doesnt-refer-to-ARGS))

Use 

    (defun my-foo-after-advice (&rest _args)

or just

    (defun my-foo-after-advice (&rest _)

> Suppose function `foo' requires 3 arguments:
>
>  (defun foo (a b c) ...)

Here you can use

    (defun foo (_a _b _c) ...)

tho you can also use

    (defun foo (&rest _) ...)

since you advice doesn't have to only accept exactly the same args as
the function it advises: it is free to accept *more* use-cases (and it's
often a good idea to do so, in case the advised function grows some
&optional arguments in the future).


        Stefan