GNU bug report logs - #24717
26.0.50; invalid-read-syntax error using Edebug on lisp/emacs-lisp/pcase.el

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Message #10 received at 24717-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Gemini Lasswell <gazally <at> runbox.com>
Cc: 24717-done <at> debbugs.gnu.org
Subject: Re: bug#24717: 26.0.50;
 invalid-read-syntax error using Edebug on lisp/emacs-lisp/pcase.el
Date: Sat, 04 Feb 2017 13:22:32 +0200

> From: Gemini Lasswell <gazally <at> runbox.com>
> Date: Mon, 17 Oct 2016 08:44:58 -0700
> 
> To reproduce, start at the top of your Emacs source tree and:
> 1. emacs -Q
> 2. M-x edebug-all-defs RET
> 3. C-x C-f lisp/emacs-lisp/pcase.el
> 4. M-x eval-buffer RET
> 
> The reason this is happening is that in this line:
> 
> (def-edebug-spec pcase-MACRO pcase--edebug-match-macro)
> 
> pcase--edebug-match-macro does not have an Edebug specification, so the
> Edebug specification for def-edebug-spec fails to match.
> 
> But when you aren't trying to debug pcase.el and are instead trying to
> debug something that uses pcase, this Edebug specification works,
> because internally to Edebug when it is trying to match an Edebug
> specification, if it finds a symbol without a specification it assumes
> it is one of Edebug's match functions and calls it. This is how Edebug
> implements the behavior for the symbols used in Edebug specifications.
> And pcase--edebug-match-macro works like one of Edebug's match
> functions.
> 
> I think it's a rather poor idea for pcase.el to depend on internal
> implementation details of Edebug. But since it does, replacing the line
> of code above with:
> 
> (put 'pcase-MACRO 'edebug-form-spec 'pcase--edebug-match-macro)
> 
> would make it more obvious that it's using internal implementation
> details of Edebug, as well as fixing the syntax error.

Thanks, I've pushed such a change.

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