http://hackage.haskell.org/package/base-4.7.0.1/docs/GHC-Stack.html#v:errorW... has been in GHC for for >=1 major version, and for normal builds, acts just like error, BUT, when an error is thrown in a profiled build, it appends a stack trace with some basic source location data to the end of the error message! I think this change would benefit many! My current understanding is that the DWARF based approach to stack traces wont make it into GHC 7.10 , and while this variant would only provide extra info in profiling builds (and strictly less than the dwarf work), its something that can definitely be done in a single small patch that could easily be swapped out for that improved approach once it lands. discussion period: 2 weeks unless theres a clear unanimous agreement to make the change ASAP, OR if the stack trace error stuff is landing in 7.10 and I'm misinformed! cheers -Carter