Add a test for trac #4444

testsuite/tests/ghc-regress/typecheck/should_compile/T4444.hs

+
+-- #4444: We shouldn't warn about SPECIALISE INLINE pragmas on
+--        non-overloaded functions
+
+{-# LANGUAGE GADTs, MagicHash #-}
+module Q where
+
+import GHC.Exts
+
+data Arr e where
+  ArrInt :: !Int -> ByteArray# -> Arr Int
+  ArrPair :: !Int -> Arr e1 -> Arr e2 -> Arr (e1, e2)
+
+(!:) :: Arr e -> Int -> e
+{-# SPECIALISE INLINE (!:) :: Arr Int -> Int -> Int #-}
+{-# SPECIALISE INLINE (!:) :: Arr (a, b) -> Int -> (a, b) #-}
+(ArrInt _ ba)     !: (I# i) = I# (indexIntArray# ba i)
+(ArrPair _ a1 a2) !: i      = (a1 !: i, a2 !: i)

testsuite/tests/ghc-regress/typecheck/should_compile/all.T

@@ -330,4 +330,5 @@ test('T4401', normal, compile, [''])
 test('T4404', expect_broken(4404), compile, ['-Wall'])
 test('HasKey', normal, compile, [''])
 test('T4418', normal, compile, [''])
+test('T4444', normal, compile, [''])