Sebastian Graf authored Sep 17, 2019 and Marge Bot committed Sep 19, 2019

Apparently ghc-lib-parser's API blew up because the newly induced cyclic
dependency between TcRnTypes and PmOracle pulled in the other half of
GHC into the relevant strongly-connected component.

This patch arranges it so that PmTypes exposes mostly data type
definitions and type class instances to be used within PmOracle, without
importing the any of the possibly offending modules DsMonad, TcSimplify
and FamInst.