Doesn't build with GHC head

[Andrew Martin]

Fails with:

src/Weigh/GHCStats.hs:19:22: error:
    • Not in scope: type constructor or class ‘GHC.Stats.GCStats’
      Perhaps you meant one of these:
        ‘GHC.Stats.RTSStats’ (imported from GHC.Stats),
        ‘GHC.Stats.GCDetails’ (imported from GHC.Stats)
      Module ‘GHC.Stats’ does not export ‘GCStats’.
    • In the Template Haskell quotation ''GHC.Stats.GCStats
      In the untyped splice:
        $(do info <- reify ''GHC.Stats.GCStats
             case info of
               TyConI (DataD _ _ _ _ [RecC _ fields] _)
                 -> do ...
                 where
                     headerSize = ...
                     ....
               _ -> fail
                      ("Unexpected shape of GCStats data type. "
                         ++ "Please report this as a bug, this function "
                         ++ "needs to be updated to the newer GCStats type."))
   |
19 |   $(do info <- reify ''GHC.Stats.GCStats
   |                      ^^^^^^^^^^^^^^^^^^^

[Andrew Martin]

nevermind. this is not actually a problem.