-- from nested matches; see the Let case of match, below
--
type SubstEnv = (TvSubstEnv, IdSubstEnv, OrdList CoreBind)
-type IdSubstEnv = IdEnv CoreExpr
+type IdSubstEnv = IdEnv CoreExpr
emptySubstEnv :: SubstEnv
emptySubstEnv = (emptyVarEnv, emptyVarEnv, nilOL)