/usr/lib/ghc-doc/hoogle/libghc-boomerang-doc.txt is in libghc-boomerang-doc 1.4.3-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-boomerang-doc/html/boomerang.txt