Language extensions are generally enabled on a per file basis. This complaint seems to be talking about tools for working with Haskell source code (such as an I

Language extensions are generally enabled on a per file basis. This complaint seems to be talking about tools for working with Haskell source code (such as an IDE). If these tools try to work with a file that has this extension enabled, then it has to be aware of what effect this extension will have, or else it may mis-parse the file. As an example, here is the first example config file for XMonad [0]. Note the "LANGUAGE" pragma, which enables a number of extensions for this file. [0] https://wiki.haskell.org/Xmonad/Config_archive/adamvo%27s_xmonad.hs https://wiki.haskell.org/Xmonad/Config_archive/adamvo%27s_xm...