users-guide: Point out GNTD may require additional extensions
authorBen Gamari <bgamari.foss@gmail.com>
Sun, 27 May 2018 15:50:21 +0000 (11:50 -0400)
committerBen Gamari <ben@smart-cactus.org>
Wed, 30 May 2018 14:02:10 +0000 (10:02 -0400)
commitb876c1bb5c8ccd73a203c0f94bac3cbb9c7e2d65
treed1c9223407546d7e1adf8ac428b59a59e62bd482
parenta4ae199cf810a63444a4ef24a44b33329023cd93
users-guide: Point out GNTD may require additional extensions

As noted in #15073, GeneralizedNewtypeDeriving may produce code that
uses extensions that do not directly appear in the code written by the
user.  Make this clear in the users guide.

[skip ci]

Test Plan: Read it

Reviewers: RyanGlScott

Reviewed By: RyanGlScott

Subscribers: fosskers, rwbarton, thomie, carter

GHC Trac Issues: #15073

Differential Revision: https://phabricator.haskell.org/D4701
docs/users_guide/glasgow_exts.rst