/usr/lib/ghc-doc/hoogle/ixset.txt is in libghc-ixset-doc 1.0.5-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-ixset-doc/html/ixset.txt
/usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-ixset-doc/html/ixset.txt