/usr/lib/ghc-doc/hoogle/libghc-th-expand-syns-doc.txt is in libghc-th-expand-syns-doc 0.4.0.0-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-th-expand-syns-doc/html/th-expand-syns.txt