+ (if binaryp 'no-conversion
+ (let ((coding-system (mm-charset-to-coding-system
+ (plist-get part :content-charset))))
+ ;; Sadly,
+ ;; `mm-charset-to-coding-system' seems
+ ;; to return things that are not
+ ;; considered acceptable values for
+ ;; `coding-system-for-read'.
+ (if (coding-system-p coding-system)
+ coding-system
+ ;; RFC 2047 says that the default
+ ;; charset is US-ASCII. RFC6657
+ ;; complicates this somewhat.
+ 'us-ascii)))))