haddock-interface-27 software package provides virtual package provided by ghc, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install haddock-interface-27
haddock-interface-27 is installed in your system.
Make ensure the haddock-interface-27 package were installed using the commands given below,
$ sudo dpkg-query -l | grep haddock-interface-27*
You will get with haddock-interface-27 package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Virtual packages |
| Package | haddock-interface-27 |
| Version | |
| Description | virtual package provided by ghc |
| Sub Section | Virtual |