Add test for Trac #3920

testsuite/tests/ghc-regress/th/T3920.hs

+{-# LANGUAGE EmptyDataDecls, TypeFamilies, TemplateHaskell #-}
+module Main where
+
+import Language.Haskell.TH
+
+type family S :: (* -> (* -> * -> *)) -> (* -> *) -> *
+
+test :: String
+test = $(do
+	test <- [d| 
+		type family T :: (* -> (* -> * -> *)) -> (* -> *) -> * |]
+        blah <- reify ''S
+	return (LitE (StringL (pprint test ++ "\n" ++ pprint blah))))
+
+main = putStrLn test

testsuite/tests/ghc-regress/th/T3920.stdout

+type family T :: (* -> * -> * -> *) -> (* -> *) -> *
+type family Main.S :: (* -> * -> * -> *) -> (* -> *) -> *

testsuite/tests/ghc-regress/th/all.T

@@ -155,6 +155,7 @@ test('T3395', normal, compile_fail, ['-v0'])
 test('T3467', normal, compile, [''])
 test('T3572', normal, compile_and_run, [''])
 test('T3100', normal, compile, ['-v0'])
+test('T3920', normal, compile_and_run, ['-v0'])
 
 test('T3600', extra_clean(['T3600a.hi','T3600a.o']), 
               multimod_compile, ['T3600','-v0'])