- -- case coerce T e of x { _ -> coerce T' x }
- -- And we definitely want to eliminate this case!
- -- So we throw away notes from the RHS, and reconstruct
- -- (at least an approximation) at the other end
- de_note (Note _ e) = de_note e
- de_note e = e
-
- -- re_note wraps a coerce if it might be necessary
- re_note scrut = case head alts of
- (_,_,rhs1@(Note _ _)) -> mkCoerce2 (exprType rhs1) (idType case_bndr) scrut
- other -> scrut
+ -- case e of x { _ -> x `cast` c }
+ -- And we definitely want to eliminate this case, to give
+ -- e `cast` c
+ -- So we throw away the cast from the RHS, and reconstruct
+ -- it at the other end. All the RHS casts must be the same
+ -- if (all identity_alt alts) holds.
+ --
+ -- Don't worry about nested casts, because the simplifier combines them
+ de_cast (Cast e _) = e
+ de_cast e = e
+
+ re_cast scrut = case head alts of
+ (_,_,Cast _ co) -> Cast scrut co
+ other -> scrut
+