Is the PatriciaTree matchGr too strict?

[noughtmare]

I was trying to figure out the time complexity of suc which lead me to the matchGr function.

fgl/Data/Graph/Inductive/PatriciaTree.hs

Lines 146 to 158 in 86dc04d

	matchGr :: Node -> Gr a b -> Decomp Gr a b
	matchGr node (Gr g)
	= case IM.lookup node g of
	Nothing
	-> (Nothing, Gr g)
	Just (p, label, s)
	-> let !g1 = IM.delete node g
	!p' = IM.delete node p
	!s' = IM.delete node s
	!g2 = clearPred g1 node s'
	!g3 = clearSucc g2 node p'
	in (Just (toAdj p', node, label, toAdj s), Gr g3)

All the work being done with the bang patterns does not seem to be necessary for the suc function as far as I can tell. I think the strict evaluation could cause the asymptotic complexity of the suc function to change from O(k + min(n,W)) (where k is the number of nodes in the output and n and W are the familiar IntMap variables) to O(n) (because of the clearPred and clearSucc functions). Should this be rewritten to:

 matchGr :: Node -> Gr a b -> Decomp Gr a b 
 matchGr node (Gr g) 
     = case IM.lookup node g of 
         Nothing 
             -> (Nothing, Gr g) 
  
         Just (p, label, s) 
             -> let g1 = IM.delete node g 
                    p' = IM.delete node p 
                    s' = IM.delete node s 
                    g2 = clearPred g1 node s' 
                    g3 = clearSucc g2 node p' 
                in (Just (p' `seq` toAdj p', node, label, toAdj s), g3 `seq` Gr g3) 

Or something similar.