/usr/lib/ghc-doc/hoogle/libghc-texmath-doc.txt is in libghc-texmath-doc 0.8.6.7-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-texmath-doc/html/texmath.txt