Test Trac #9750

2 files changed, 35 insertions, 0 deletions

diff --git a/testsuite/tests/polykinds/T9750.hs b/testsuite/tests/polykinds/T9750.hs
new file mode 100644
index 0000000000..9d865d08f6
--- /dev/null
+++ b/testsuite/tests/polykinds/T9750.hs
@@ -0,0 +1,34 @@
+{-# LANGUAGE FlexibleInstances      #-}
+{-# LANGUAGE TypeFamilies           #-}
+{-# LANGUAGE DataKinds              #-}
+{-# LANGUAGE ScopedTypeVariables    #-}
+
+module T9750 where
+
+import GHC.TypeLits ( Symbol, KnownSymbol )
+
+--------------------------------------------------------------------------------
+
+data Meta = MetaCons Symbol
+data M1 (c :: Meta) = M1
+
+class Generic a where
+  type Rep a :: *
+  from  :: a -> Rep a
+
+--------------------------------------------------------------------------------
+
+data A = A1
+
+instance Generic A where
+  type Rep A = M1 ('MetaCons "test")
+  from A1 = M1
+
+class GShow' f where
+  gshowsPrec' :: f -> ShowS
+
+instance (KnownSymbol c) => GShow' (M1 ('MetaCons c)) where
+  gshowsPrec' = error "urk"
+
+instance GShow' A where
+  gshowsPrec' = gshowsPrec' . from
diff --git a/testsuite/tests/polykinds/all.T b/testsuite/tests/polykinds/all.T
index 5b02dda80c..48b0e61b5e 100644
--- a/testsuite/tests/polykinds/all.T
+++ b/testsuite/tests/polykinds/all.T
@@ -108,3 +108,4 @@ test('T9263', normal, run_command, ['$MAKE -s --no-print-directory T9263'])
 test('T9063', normal, compile, [''])
 test('T9200', normal, compile, [''])
 test('T9200b', normal, compile_fail, [''])
+test('T9750', normal, compile, [''])