GNU bug report logs - #16567
24.3.50; pcase should signal an error if no case matches

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Package: emacs;

Reported by: Helmut Eller <eller.helmut <at> gmail.com>

Date: Mon, 27 Jan 2014 09:24:01 UTC

Severity: wishlist

Found in version 24.3.50

Fixed in version 25.1

Done: Leo Liu <sdl.web <at> gmail.com>

Bug is archived. No further changes may be made.

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Message #26 received at 16567 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Helmut Eller <eller.helmut <at> gmail.com>
Cc: 16567 <at> debbugs.gnu.org
Subject: Re: bug#16567: 24.3.50;
 pcase should signal an error if no case matches
Date: Mon, 08 Sep 2014 20:41:01 -0400

> What could happen if you would change it?

Obviously: errors signaled instead of returning the expected nil.
Returning nil by default is "the norm" in Elisp (think of missing `else'
branches in `if', or missing default case in `cond' or even missing
default case in `cl-case'), so it's to be expected that pcase users
would rely on this default behavior as well, even if it strikes you as
utter nonsense.

> The "nil default" would make more sense in a pcase-if or pif macro.

Changing the default of `pcase' is not an option at this point.


        Stefan
This bug report was last modified 10 years and 290 days ago.

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