From b08a6d75e0440f33260bea5319b8c3f871b42f6e Mon Sep 17 00:00:00 2001
From: Ryan Scott <ryan.gl.scott@gmail.com>
Date: Thu, 19 Apr 2018 12:36:42 -0400
Subject: Fix #15012 with a well-placed use of Any

Previously, derived `Generic1` instances could have associated `Rep1`
type family instances with unbound variables, such as in the following
example:

```lang=haskell
data T a = MkT (FakeOut a) deriving Generic1
type FakeOut a = Int

==>

instance Generic1 T where
  type Rep1 T = ... (Rec0 (FakeOut a))
```

Yikes! To avoid this, we simply map the last type variable in a
derived `Generic1` instance to `Any`.

Test Plan: make test TEST=T15012

Reviewers: bgamari

Reviewed By: bgamari

Subscribers: simonpj, thomie, carter

GHC Trac Issues: #15012

Differential Revision: https://phabricator.haskell.org/D4602
---
 testsuite/tests/generics/Makefile   |  5 +++++
 testsuite/tests/generics/T15012.hs  |  7 +++++++
 testsuite/tests/generics/T15012a.hs | 11 +++++++++++
 testsuite/tests/generics/all.T      |  2 ++
 4 files changed, 25 insertions(+)
 create mode 100644 testsuite/tests/generics/T15012.hs
 create mode 100644 testsuite/tests/generics/T15012a.hs

(limited to 'testsuite')

diff --git a/testsuite/tests/generics/Makefile b/testsuite/tests/generics/Makefile
index 9a36a1c5fe..69a5802b96 100644
--- a/testsuite/tests/generics/Makefile
+++ b/testsuite/tests/generics/Makefile
@@ -1,3 +1,8 @@
 TOP=../..
 include $(TOP)/mk/boilerplate.mk
 include $(TOP)/mk/test.mk
+
+T15012:
+	$(RM) T15012.hi T15012.o T15012a.hi T15012a.o
+	'$(TEST_HC)' $(TEST_HC_OPTS) -c T15012a.hs
+	'$(TEST_HC)' $(TEST_HC_OPTS) -c T15012.hs
diff --git a/testsuite/tests/generics/T15012.hs b/testsuite/tests/generics/T15012.hs
new file mode 100644
index 0000000000..388eddc0ed
--- /dev/null
+++ b/testsuite/tests/generics/T15012.hs
@@ -0,0 +1,7 @@
+module T15012 where
+
+import GHC.Generics
+import T15012a
+
+blah :: IO ()
+blah = print $ from1 $ TyFamily 1 2
diff --git a/testsuite/tests/generics/T15012a.hs b/testsuite/tests/generics/T15012a.hs
new file mode 100644
index 0000000000..5109ea08f0
--- /dev/null
+++ b/testsuite/tests/generics/T15012a.hs
@@ -0,0 +1,11 @@
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE TypeFamilies #-}
+module T15012a where
+
+import GHC.Generics
+
+type FakeOut a = Int
+
+data family   TyFamily y z
+data instance TyFamily a b = TyFamily Int (FakeOut b)
+  deriving Generic1
diff --git a/testsuite/tests/generics/all.T b/testsuite/tests/generics/all.T
index 1d4aeaee38..f127f7895f 100644
--- a/testsuite/tests/generics/all.T
+++ b/testsuite/tests/generics/all.T
@@ -43,3 +43,5 @@ test('T10361a', normal, compile, [''])
 test('T10361b', normal, compile, [''])
 test('T11358', normal, compile_and_run, [''])
 test('T12220', normal, compile, [''])
+test('T15012', [extra_files(['T15012.hs', 'T15012a.hs'])], run_command,
+               ['$MAKE -s --no-print-directory T15012'])
-- 
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