Re: Declaring a local dynamic variable?

[Andreas Röhler]

Am 21.09.2013 13:31, schrieb Barry Margolin:
> In article <mailman.2622.1379742443.10748.help-gnu-emacs@gnu.org>,
>   Andreas Röhler <andreas.roehler@easy-emacs.de> wrote:
>
> > Am 20.09.2013 22:59, schrieb Barry Margolin:
> > > In article <mailman.2578.1379694764.10748.help-gnu-emacs@gnu.org>,
> > >    Andreas Röhler <andreas.roehler@easy-emacs.de> wrote:
> > >
> > > > Am 20.09.2013 17:10, schrieb Barry Margolin:
> > > > > In article <mailman.2569.1379688787.10748.help-gnu-emacs@gnu.org>,
> > > > >     Andreas Röhler <andreas.roehler@easy-emacs.de> wrote:
> > > > >
> > > > > > Am 20.09.2013 14:30, schrieb Stefan Monnier:
> > > > > > > > If I purposefully use a local dynamic variable as in:
> > > > > > >
> > > > > > > Use (defvar my-counter) at the file's top-level to indicate that this
> > > > > > > variable is used in a way that relies on dynamic scoping.
> > > > > >
> > > > > > A need to write code just to silence compiler warnings?
> > > > > > Emacs could do better.
> > > > >
> > > > > Other than "code", what would you suggest?
> > > >
> > > > In the precise case: just drop that warning.
> > > >
> > > > In a wider sense, IMO a modular approach is better.
> > > > Restrict compiler warnings to obvious errors, don't mix style questions in.
> > >
> > > This isn't a style warning. Often the reason is mistyping a local
> > > variable name.
> > >
> > > (let ((foobar ...))
> > >      ...
> > >      (blah fobar)
> > >      ...)
> >
> > This is another case. IIUC there was nothing wrong with the OP's example.
>
> But how is the compiler supposed to know the difference?

A code-checker might look up, if a variable is defined.
If our eyes may notice the difference, why a checker should not?

 Either it
> always warns, and generate false positives when you compile the user of
> a variable before loading the defvar, or never warns and there are false
> negatives when the user makes a typo.
>
> In this case, false positives are the better option, since you can
> easily silence them by adding a defvar. If the warning were removed,
> there's no way to get the warning when you actually do make a typo.

Unfortunatly it's not the only occassion. Compiler message is cluttered with 
false positives that way.