This issue dates back to some commits I merged recently, which made encodings
like Shift-JIS-2004 use appropriate JIS X 0208 characters to represent
backslashes and tildes, rather than single-byte characters which are used in
those encodings with a different meaning (for example, in these encodings,
0x5C is used for a halfwidth Yen sign, rather than a backslash).
There was an unintended side effect: ISO-2022-JP-2004 was also made to
represent backslashes and tildes using JIS X 0208 characters. However,
ISO-2022-JP explicitly includes ASCII as one of its selectable character sets,
and ISO-2022-JP-2004 is just an extension of ISO-2022-JP. So when converting
text to ISO-2022-JP-2004, we can convert Unicode backslashes and tildes to ASCII
rather than using the corresponding JIS X 0208 characters.
Alex Dowad
4d65c2a992