(Please keep the bug address in CC when replying.)

Hello Pierre,

Sorry that it took me so long to see your reply.

On 18/6/20 17:47, Pierre Rouleau wrote:

> You are correct.  If a symbol used in the default happens to be
> unbounded when the customize UI is opened, the UI fails and reports a
> "mismatch".

Thanks for confirming.

> I was misled by the term 'mismatch' because I thought the data
> structure definition was wrong.  I did not look at the code of the
> customize UI enough to see if it was able to handle all types of
> errors, but maybe it would be possible to distinguish a real mismatch
> from an attempt to eval an unbound symbol (in either space: function
> or variable).  I think it would help people understand the mistake
> they made in their code or to the data a little bit more, which might
> help to make the Emacs customize system a little more user friendly.

There was a real mismatch.  Custom checks if the current value matches
the specification given.  If it doesn't match, then it reports that
there is a mismatch, but still lets you edit the value of the variable.

> Should I enter another request for an enhancement instead?

I'm not sure something should be done here, but I'm far from being an
active contributor or an expert, so I'll let more experienced people
weigh in.