Map.! when compiling with --debug #1851
Many people have reported this bug. I am collecting them here with labels about the nature of the SSCCE they provide:
This will make it easier to test a fix against them all.
If you are seeing this bug, please open a new issue with an http://sscce.org/ that demonstrates it. The point of a meta issue is to recognize issues that are caused by the root bug, rather than having chaotic threads of discussion where the participants may actually be seeing different bugs but have not shared an SSCCE of their own.