nubBy flips args to nubbing function

The nubBy function in the List library seems to flip
the order of arguments to the nubbing function from
that specified in the prelude:

nubBy eq (x:xs)         =  x : nubBy eq (filter (\y ->
not (eq x y)) xs)

I.e., it seems to use (eq y x) instead of (eq x y). 
This doesn't matter of course for symmetric nubbing
functions, but I just tried to use it with the
following function:

subsetEq :: (Eq a) => [a] -> [a] -> Bool
subsetEq l1 l2 = all (`elem` l2) l1

> nubBy subsetEq [[1],[1,2],[2,3],[2]] 
[[1],[1,2],[2,3]]

> nubBy (flip subsetEq) [[1],[1,2],[2,3],[2]]
[[1],[2,3],[2]]

Trac metadata

Trac field	Value
Version	5.0
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	ResolvedRemind
Component	None
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