GHC developers
You may be interested in this paper, submitted to ICFP
GADTs meet their match: pattern-matching warnings that account for GADTs, guards, and laziness, with Georgios
Karachalias, Tom Schrijvers, and Dimitrios Vytiniotis.
It describes a GADT-aware algorithm for detecting missing and redundant patterns.
The implementation is not yet up to production quality, but it will be!
If you feel able to give us any feedback about the paper itself, that would be incredibly useful. Thanks
Simon