The Generate.hs program is intended to be run from "runghc" or
"runhugs" in the src directory.  It only gets run once per build to
generate the src/Layer/Types.hs file from the XML specification.

This directory contains Types-exports.hs and Types.hs.  These are the
two fragments of constant text that are incorporated into the final
Types.hs file.  They retain the ".hs" suffix so that they can be
edited in Haskell mode.