Re: functionp bug

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I think that change in functionp should be reverted.  Any change in
> such things tends to cause problems, so it is better to leave them alone
> unless there is an important problem to be fixed.

The old definition lead to bugs in *all* uses I've seen.  All the uses
I've seen fall in the following 2 categories:
1 - (if (functionp <foo>) (funcall <foo> ...))
    with the old definition, this signalled an error if <foo> was
    a special form.
2 - the kind of use that is discussed in this thread, where the code
    wants to check "can <foo> be the `car' of an valid Elisp
    expression", where using `functionp' made the test reject uses of
    `when' while it accepted uses of `if'.

> Theoretical arguments trying to show that "this behavior couldn't
> possibly be right for any caller" tend to be unreliable.  Whatever
> functionp does, code will have come to depend on it.

Yes, the change is an incompatible one.  But it will get rid of bugs.


        Stefan