GNU bug report logs - #50219
28.0.50; Provide better errors when trying to specialize on optional args in generic methods

Previous Next

Full log

View this message in rfc822 format

From: Eric Abrahamsen <eric <at> ericabrahamsen.net>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: Lars Ingebrigtsen <larsi <at> gnus.org>, 50219 <at> debbugs.gnu.org
Subject: bug#50219: 28.0.50; Provide better errors when trying to specialize on optional args in generic methods
Date: Sat, 28 Aug 2021 17:47:12 -0700

On 08/28/21 13:41 PM, Stefan Monnier wrote:
>> (cl-defmethod foo ((a integer) &optional (b string))
>>   ...)
>>
>> on the other hand, looks like the person who wrote it wanted to
>> specialise on b, so if the default is something that is a type
>> specifier, then we could output an additional warning about that.
>
> The default value part of args in Common lisp arglists is an
> *expression*, so (b string) just means that `b` should take the value of
> the `string` variable.
>
> The best I can see (if we keep the CL arglist feature) is to try and see
> if that expression looks like a valid CLOS specializer and if so emit
> a warning about possible confusion.

That's a pretty byzantine set of rules! Anyway, I think "reference to
free variable string" is probably close enough to clue the developer in
to what is happening. In the case of an EIEIO class name, though, the
error was:

"`ebdb-record' is an obsolete variable, use `ebdb-record' instead"

which is just...

So maybe something special for class and struct types would be sufficient?

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.