IntSet's minView and maxView creates unwanted thunks

[meooow25]

containers/containers/src/Data/IntSet/Internal.hs

Lines 1164 to 1172 in 0c3b9ee

	maxView :: IntSet -> Maybe (Key, IntSet)
	maxView t =
	case t of Nil -> Nothing
	Bin p l r | signBranch p -> case go l of (result, l') -> Just (result, binCheckL p l' r)
	_ -> Just (go t)
	where
	go (Bin p l r) = case go r of (result, r') -> (result, binCheckR p l r')
	go (Tip kx bm) = case highestBitSet bm of bi -> (kx + bi, tip kx (bm .&. complement (bitmapOfSuffix bi)))
	go Nil = error "maxView Nil"

Core:

Rec {
-- RHS size: {terms: 47, types: 28, coercions: 0, joins: 0/1}
$wgo1 [InlPrag=[2], Occ=LoopBreaker] :: IntSet -> (# Int, IntSet #)
[GblId[StrictWorker([!])], Arity=1, Str=<1L>, Unf=OtherCon []]
$wgo1
  = \ (ds_sdOH :: IntSet) ->
      case ds_sdOH of {
        Bin bx_dcyn l_a73T r_a73U ->
          case $wgo1 r_a73U of { (# ww_se6X, ww1_se6Y #) ->
          (# ww_se6X,
             case ww1_se6Y of wild2_X4 {
               __DEFAULT -> Bin bx_dcyn l_a73T wild2_X4;
               Nil -> l_a73T
             } #)
          };
        Tip bx_dcyp bx1_dcyq ->
          let {
            bi_sd64 :: Int#
            [LclId]
            bi_sd64 = -# 63# (word2Int# (clz# bx1_dcyq)) } in
          (# I# (+# bx_dcyp bi_sd64),
             case and# bx1_dcyq (not# (uncheckedShiftL# 1## bi_sd64))
             of ds1_X3 {
               __DEFAULT -> Tip bx_dcyp ds1_X3;
               0## -> Nil
             } #);
        Nil -> case lvl42_reKj of {}
      }

Just using a strict pair instead of lazy should fix it. IntMap's definition seems pretty good and how I would define it for IntSet too, splitting the empty map case out and inlining it to potentially get rid of the Maybe.

containers/containers/src/Data/IntMap/Internal.hs

Lines 2325 to 2345 in 0c3b9ee

	maxViewWithKey :: IntMap a -> Maybe ((Key, a), IntMap a)
	maxViewWithKey t = case t of
	Nil -> Nothing
	_ -> Just $ case maxViewWithKeySure t of
	View k v t' -> ((k, v), t')
	{-# INLINE maxViewWithKey #-}
	maxViewWithKeySure :: IntMap a -> View a
	maxViewWithKeySure t =
	case t of
	Nil -> error "maxViewWithKeySure Nil"
	Bin p l r | signBranch p ->
	case go l of View k a l' -> View k a (binCheckL p l' r)
	_ -> go t
	where
	go (Bin p l r) =
	case go r of View k a r' -> View k a (binCheckR p l r')
	go (Tip k y) = View k y Nil
	go Nil = error "maxViewWithKey_go Nil"
	-- See note on NOINLINE at minViewWithKeySure
	{-# NOINLINE maxViewWithKeySure #-}