The HList library

(C) 2004, Oleg Kiselyov, Ralf Laemmel, Keean Schupke

A generic implementation of type cast. For this implementation to work, we need to import it at a higher level in the module hierarchy than all clients of the class. Otherwise, type simplification will inline TypeCast x y, which implies compile-time unification of x and y.

This technique works fine for ghc, and within limits for hugs.