bug#2052: 23.0.60; byte-compiled Emacs Lisp files are not shown during find-file completion

[Eli Zaretskii <eliz@gnu.org>]

> From: Brent Goodrick <bgoodr@gmail.com>
> Date: Sun, 25 Jan 2009 10:13:36 -0800
> Cc: 
> 
> Using Emacs built from top of trunk CVS today.  Validated this using
> emacs -q. Do the following:
> 
> 1. Open up the *scratch* (lisp-interaction-mode) buffer and evaluate
> the following form which simply compiles the .el file into a .elc
> file for demonstration purposes:
> 
> (let* ((elisp-file "/tmp/afile.el")
>        (byte-compiled-file (concat elisp-file "c")))
>   (find-file elisp-file)
>   (erase-buffer)
>   (insert (format "%S" '(message "just some message")))
>   (save-buffer)
>   (when (file-exists-p byte-compiled-file)
>     (message "Deleting byte-compiled file %S" byte-compiled-file)
>     (delete-file byte-compiled-file))
>   (byte-compile-file elisp-file)
>   (unless (file-exists-p byte-compiled-file)
>     (error "Assertion failed: .elc %S should exist. What happened?" byte-compiled-file))
>   (message "Created byte-compiled file %s" byte-compiled-file))
> 
> 2. Execute M-x find-file
> 
> 3. Type in "/tmp/afile.el" (without the double-quotes) and then hit
> the TAB key twice.  It reads "Sole completion" for only the .el file,
> which wrong because the .elc file does indeed exist.  The
> /tmp/afile.elc file exists as you can tell by examining the
> filesystem.

Does the value of completion-ignored-extensions give you a hint why
this is a feature?