add test for #2685

testsuite/tests/ghc-regress/th/T2685.hs

+{-# LANGUAGE TemplateHaskell #-}
+module T2685 where
+
+import T2685a
+
+$( th )

testsuite/tests/ghc-regress/th/T2685a.hs

+{-# LANGUAGE TemplateHaskell #-}
+module T2685a (th) where
+
+import Language.Haskell.TH
+
+newtype NT = C (() -> ())
+
+th :: Q [Dec]
+th = [d| foo = C undefined |]

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

@@ -120,3 +120,5 @@ test('T2386', extra_clean(['T2386_Lib.hi', 'T2386_Lib.o']),
 	      run_command,
 	      ['$MAKE -s --no-print-directory T2386'] )
 test('TH_emptycase', exit_code(1), compile_and_run, [''])
+
+test('T2685', normal, multimod_compile, ['T2685','-v0'])