Add InjectiveTypeFamilies language extension

Previously injective type families were part of TypeFamilies.
Now they are in a separate language extension.

Test Plan: ./validate

Reviewers: austin, bgamari, goldfire

Reviewed By: bgamari

Subscribers: goldfire, thomie

Differential Revision: https://phabricator.haskell.org/D1750

GHC Trac Issues: #11381

4 files changed, 17 insertions, 1 deletions

diff --git a/testsuite/tests/driver/T11381.hs b/testsuite/tests/driver/T11381.hs
new file mode 100644
index 0000000000..8dc94dd8a7
--- /dev/null
+++ b/testsuite/tests/driver/T11381.hs
@@ -0,0 +1,9 @@
+{-# LANGUAGE TypeFamilies #-}
+
+module T11381 where
+
+-- ensure that this code does not compile without InjectiveTypeFamilies and that
+-- injectivity error is not reported.
+type family F a = r | r -> a
+type instance F Int = Bool
+type instance F Int = Char
diff --git a/testsuite/tests/driver/T11381.stderr b/testsuite/tests/driver/T11381.stderr
new file mode 100644
index 0000000000..afe652d38e
--- /dev/null
+++ b/testsuite/tests/driver/T11381.stderr
@@ -0,0 +1,5 @@
+
+T11381.hs:7:23:
+     Illegal injectivity annotation
+      Use InjectiveTypeFamilies to allow this
+     In the type family declaration for ‘F’
diff --git a/testsuite/tests/driver/T4437.hs b/testsuite/tests/driver/T4437.hs
index 5f14da1a9a..cbf71868bd 100644
--- a/testsuite/tests/driver/T4437.hs
+++ b/testsuite/tests/driver/T4437.hs
@@ -38,7 +38,8 @@ check title expected got
 expectedGhcOnlyExtensions :: [String]
 expectedGhcOnlyExtensions = ["RelaxedLayout",
                              "AlternativeLayoutRule",
-                             "AlternativeLayoutRuleTransitional"]
+                             "AlternativeLayoutRuleTransitional",
+                             "InjectiveTypeFamilies"]
 
 expectedCabalOnlyExtensions :: [String]
 expectedCabalOnlyExtensions = ["Generics",
diff --git a/testsuite/tests/driver/all.T b/testsuite/tests/driver/all.T
index 8493aa4c57..e0022d7d60 100644
--- a/testsuite/tests/driver/all.T
+++ b/testsuite/tests/driver/all.T
@@ -466,3 +466,4 @@ test('T10970', normal, compile_and_run, ['-hide-all-packages -package base -pack
 test('T10970a', normal, compile_and_run, [''])
 test('T4931', normal, compile_and_run, [''])
 test('T11182', normal, compile_and_run, [''])
+test('T11381', normal, compile_fail, [''])