GHC.Ix.indexError no longer exported
base 4.14, the
Ix typeclass's definition has been moved from
GHC.Ix. However, the move didn't preserve the old
GHC.Arr API; in particular, the
indexError function is no longer exported.
indexError is useful when writing your own
Ix instances, so it should be available to third-party code that creates new instances.