+
+-- The ModDetails takes on several slightly different forms:
+--
+-- After typecheck + desugar
+-- md_types Contains TyCons, Classes, and implicit Ids
+-- md_insts All instances from this module (incl derived ones)
+-- md_rules All rules from this module
+-- md_binds Desugared bindings
+--
+-- After simplification
+-- md_types Same as after typecheck
+-- md_insts Ditto
+-- md_rules Orphan rules only (local ones now attached to binds)
+-- md_binds With rules attached
+--
+-- After CoreTidy
+-- md_types Now contains Ids as well, replete with final IdInfo
+-- The Ids are only the ones that are visible from
+-- importing modules. Without -O that means only
+-- exported Ids, but with -O importing modules may
+-- see ids mentioned in unfoldings of exported Ids
+--
+-- md_insts Same DFunIds as before, but with final IdInfo,
+-- and the unique might have changed; remember that
+-- CoreTidy links up the uniques of old and new versions
+--
+-- md_rules All rules for exported things, substituted with final Ids
+--
+-- md_binds Tidied
+--
+-- Passed back to compilation manager
+-- Just as after CoreTidy, but with md_binds nuked
+