Unsupported extension [GHC-46537]

This error is reported when GHC fails to recognize the name of a language extension, provided via {-# LANGUAGE ... #-} pragma at the top of a .hs file.

There are two likely causes:

  1. You’ve made a typo, in which case GHC will likely also suggest the correct extension name to use.

  2. You’re using older version of GHC that doesn’t yet support the extension. Here’s a couple of things you can try in order to troubleshoot:

    • Find out which version of GHC you’re using:

      ghc --version
    • List all the supported extensions that this version of GHC supports. Does the list contain your desired extension?

      ghc --supported-extensions
    • Search for the extension name in the latest version of the GHC User’s Guide. Most extensions have a since annotation which tells you in which version of GHC the extension was introduced.


Unsupported extension

Error Message

Main.hs:1:14: error: [GHC-46537]
    Unsupported extension: ExistientialQuantification
    Suggested fix:
      Perhaps you meant ‘ExistentialQuantification’ or ‘NoExistentialQuantification’
1 | {-# LANGUAGE ExistientialQuantification #-}
  |              ^^^^^^^^^^^^^^^^^^^^^^^^^^
{-# LANGUAGE ExistientialQuantification #-}
-- typo here      ^                
module UnsupportedExtension where
{-# LANGUAGE ExistentialQuantification #-}

module UnsupportedExtension where