Hi all, I have been manipulating CoreExpr to convert it to A-Normal Form. Mostly, things have been working fine, but I hit an error this morning of the form: lq_anf__d11u is out of scope where lq_anf__d11u is a binder I have introduced in the transformed expression Data.ByteString.Internal.c_strlen = (\ (ds_d11l :: GHC.Ptr.Ptr Foreign.C.Types.CChar) -> case ds_d11l of lq_anf__d11t { GHC.Ptr.Ptr ds_d11n -> let { lq_anf__d11x :: GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, GHC.Word.Word32 #) [LclId] lq_anf__d11x = \ (ds_d11q :: GHC.Prim.State# GHC.Prim.RealWorld) -> case {__pkg_ccall main strlen GHC.Prim.Addr# -> GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, GHC.Prim.Word# #)} ds_d11n ds_d11q of lq_anf__d11u { __DEFAULT -> case lq_anf__d11u of lq_anf__d11v { (# ds_d11p, ds_d11o #) -> let { lq_anf__d11w :: GHC.Word.Word32 [LclId] lq_anf__d11w = GHC.Word.W32# ds_d11o } in (# ds_d11p, lq_anf__d11w #) } } } in GHC.Types.IO @ GHC.Word.Word32 lq_anf__d11x }) It would appear, that the variable IS in scope (as it is bound by the case-expression just before it is used, but perhaps the binder is not added to the environment because of its type (# ... , ... #)? Or is there some other invariant I am breaking? Can anyone familiar with the scoping invariants of CoreExpr/CoreSyn give me a hint as to what might be happening? Many thanks in advance! Ranjit.