Update the "disjointX" variants to use IntMap.disjoint
IntMap
(and Map
) have gained dedicated disjoint
functions in containers-0.6.2.1, which will be bundled with GHC-8.8.
That means that we can start using these functions in GHC-8.12.
At that point we should update disjointUFM
, disjointUDFM
etc. to use the new functions.