/usr/lib/ghc-doc/hoogle/libghc-sendfile-doc.txt is in libghc-sendfile-doc 0.7.9-6.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-sendfile-doc/html/sendfile.txt