bug#40407: [PATCH] slow ENCODE_FILE and DECODE_FILE

[Mattias Engdegård]

6 apr. 2020 kl. 20.34 skrev OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>:

> (check-coding-systems-region "あ" nil '(utf-7-imap))
> => ((utf-7-imap 0))
> 
> It says "cannot encodable by utf-7-imap", so looks like ":charset-list
> '(ascii)" doesn't work at least.

Thanks for catching that! The documentation doesn't explain the role of 
:charset-list for a :coding-type of 'utf-8, but a minimal patch seemed to work. 
Your example has been added to the test.