This is a Haskell implementation of the Region Calculus proposed by Fluet and Morrisett [1]. This works on the C Heap and uses a notion of type level equality to encode region subtyping. This is based on Oleg Kiselyov's work on monadic regions for file handles[2].
[1] Fluet, M. and Morrisett, G., 2004, September. Monadic regions. In ACM SIGPLAN Notices (Vol. 39, No. 9, pp. 103-114). ACM.
[2] Kiselyov, O. and Shan, C.C., 2008, September. Lightweight monadic regions. In Haskell (Vol. 8, pp. 1-12).