bollmann authored Mar 11, 2016 and Ben Gamari committed Mar 11, 2016

The original TH failure observed by the ticket, namely that Template
Haskell quotes of data instance GADTs are broken, is not observable
anymore in HEAD. I therefore just added the corresponding regression
test.

Test Plan: ./validate

Reviewers: goldfire, austin, thomie, jstolarek, bgamari

Reviewed By: bgamari

Differential Revision: https://phabricator.haskell.org/D1978

GHC Trac Issues: #11145