Data.Map.Strict.mergeWithKey does not force the result of the combining function

[meooow25]

mergeWithKey should force x':

containers/containers/src/Data/Map/Strict/Internal.hs

Lines 1251 to 1253 in 96a8dec

	Just x2 -> case f kx x x2 of
	Nothing -> link2 l' r'
	Just x' -> link kx x' l' r'

Found in #1021

---

IntMap seems fine

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

Lines 760 to 761 in 96a8dec

	combine = \(Tip k1 x1) (Tip _k2 x2) -> case f k1 x1 x2 of Nothing -> Nil
	Just !x -> Tip k1 x

[treeowl]

Good catch. I wonder if that's been there forever or if I accidentally introduced it with the merge algorithm change.... If it was my fault, I'm sorry. Fortunately, almost no one uses this hideous function.

[meooow25]

Looks like it's been there since the function was introduced.

Fortunately, almost no one uses this hideous function.

We can fix it now, but do we plan to remove it at some point?

[treeowl]

I tried a few years ago, but one or two people opposed it.

[meooow25]

Oh well, at least it has good documentation explaining how it is unsafe.

[treeowl]

We should also document that the function doesn't crack open the replacement trees to force values within.