Record syntax and INLINE annotations

[Bryan O'Sullivan]

Simon Peyton-Jones wrote:
> can you give an example?

Certainly.  This comes from the bloomfilter package on Hackage.

type Hash = Word32

data MBloom s a = MB {
      hashMB :: {-# UNPACK #-} !(a -> [Hash])
    , shiftMB :: {-# UNPACK #-} !Int
    , maskMB :: {-# UNPACK #-} !Int
    , bitArrayMB :: {-# UNPACK #-} !(STUArray s Int Hash)
    }

insertMB :: MBloom s a -> a -> ST s ()
{-# SPECIALIZE insertMB
        :: MBloom s SB.ByteString -> SB.ByteString -> ST s () #-}
insertMB mb elt = do
  let mu = bitArrayMB mb
  forM_ (hashesM mb elt) $ \(word :* bit) -> do
      old <- unsafeRead mu word
      unsafeWrite mu word (old .|. (1 `shiftL` bit))

If I look at the Core generated for any version of insertMB, specialised
or not, I see the following.  Note the non-inlined uses of maskMB and
bitArrayMB.  (I export bitArrayMB from the module, but not maskMB.)

Data.BloomFilter.insertMB =
  \ (@ s_a2ta)
    (@ a_a2tb)
    (mb_X2n2 :: Data.BloomFilter.MBloom s_a2ta a_a2tb)
    (elt_X2n4 :: a_a2tb) ->
    __letrec {
      a2_s3g9 :: [Word32]
                 -> State# s_a2ta
                 -> (# State# s_a2ta, () #)
      [Arity 2

      a2_s3g9 =
        \ (ds_a2S9 :: [Word32]) (eta_s37Y :: State# s_a2ta) ->
          case ds_a2S9 of wild_a2Sa {
            [] -> (# eta_s37Y, () #);
            : y_a2Se ys_a2Sf ->
              case y_a2Se of wild1_a2Io { W32# x#_a2Iq ->
              case Data.BloomFilter.maskMB @ s_a2ta @ a_a2tb mb_X2n2
              of wild11_a2T0 { I# y#_a2T2 ->
              case Data.BloomFilter.bitArrayMB @ s_a2ta @ a_a2tb mb_X2n2
              of wild2_a2P0
              { Data.Array.Base.STUArray ds2_a2P2 ds3_a2P3 ds4_a2P4
marr#_a2P5 -> [......]

If I switch to non-record syntax, the inliner does the right thing.

	<b