/usr/lib/ghc-doc/hoogle/mersenne-random.txt is in libghc-mersenne-random-doc 1.0.0.1-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-mersenne-random-doc/html/mersenne-random.txt