/usr/lib/ghc-doc/hoogle/either.txt is in libghc-either-doc 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-either-doc/html/either.txt
/usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-either-doc/html/either.txt