niteria authored May 22, 2017 and Ben Gamari committed May 22, 2017

Based on my quick search, we don't have a test
that verifies that we check the type family instances of
currently compiled module against direct or indirect
dependencies.

This adds two tests: for a direct dependency and
for an indirect dependency.

I also added a comment to make it clear what the 'Over'
test tests.

Other than completeness, it makes sense to have these
tests because if you look at
Note [The type family instance consistency story] in FamInsts
these cases are checked through different mechanisms.

Test Plan: new tests

Reviewers: simonmar, rwbarton, simonpj, austin, bgamari

Reviewed By: simonpj, bgamari

Subscribers: thomie

GHC Trac Issues: #13719

Differential Revision: https://phabricator.haskell.org/D3602