This is a workaround answer rather than a direct one, but I've taken to storing all my vim backups/swap files in a single designated directory rather than scattered around. (I want them to exist, but I don't want them cluttering up my working space.) Put this in your .vimrc file (and create whatever directories you specify):

set backupdir=~/.vimbackups//
set directory=~/.vimswap//
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The double backslash makes vim convert the full pathname of your file into the name of the swap/backup files created. Read ":h dir" and ":h bdir" for details.