bug#31314: 26.1; using % escapes in prompt for interactive

[Lars Ingebrigtsen <larsi@gnus.org>]

"Roland Winkler" <winkler@gnu.org> writes:

> Running the following command interactively in emacs -Q
>
>    (defun foo-num (n1 n2)
>      "Display numbers N1 and N2."
>      (interactive "nNumber 1: \nnNumber 1: %e, Number 2: ")
>      (message "Number 1: %9.2e, Number 2: %e" n1 n2))
>
> yields the error message
>
>   Format specifier doesn?FFE2?FF80?FF99t match argument type
>
> The problem is the `%e' apearing in the prompt for `interactive'.
> If this is replaced by a generic `%s' everything works fine.
>
> The docstring of `interactive' says that the % escapes can be used
> as in calls of `format', which sugests to me that these escapes
> should match the data types of the arguments that have already been
> read.  Yet it seems that in this context the previously read
> arguments are interpreted as strings.  So either the docstring of
> `interactive' should say that one may use %s escapes for all types
> of arguments or something else should be fixed to make this work
> with any type of arguments.

I changed the doc string to say "%s", since that's apparently the only
thing allowed currently.  Extending `interactive' to allow
other types may be nice, though.

-- 
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   bloggy blog: http://lars.ingebrigtsen.no