Use Data.Map.Strict for Ixed Map?

[goertzenator]

The Ixed instance for Map uses functions from Data.Map.Lazy (redirects from Data.Map). Lazy map functions are prone to creating space leaks, and well, this is what happened to me. My app carefully uses strict maps everywhere, but some lens use quietly introduced laziness in exactly the wrong spot to create a hard to diagnose space leak.

Another point: The documentation in Data.Map recommends the use of Data.Map.Strict instead of Data.Map.Lazy, so the Ixed instance should probably use strict functions too.