From e8ba63274102a0de17227b46729ca3e22b861a23 Mon Sep 17 00:00:00 2001
From: Son Ho
Date: Wed, 27 Apr 2022 13:57:35 +0200
Subject: Fix the filtering of useless backward functions

---
 src/PureMicroPasses.ml | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/PureMicroPasses.ml b/src/PureMicroPasses.ml
index 75844345..2c4c667f 100644
--- a/src/PureMicroPasses.ml
+++ b/src/PureMicroPasses.ml
@@ -959,9 +959,14 @@ let filter_useless (filter_monadic_calls : bool) (ctx : trans_ctx)
   *)
 let filter_if_backward_with_no_outputs (config : config) (def : fun_decl) :
     fun_decl option =
+  let return_ty =
+    if config.use_state_monad then
+      mk_result_ty (mk_simpl_tuple_ty [ mk_state_ty; unit_ty ])
+    else mk_result_ty (mk_simpl_tuple_ty [ unit_ty ])
+  in
   if
     config.filter_useless_functions && Option.is_some def.back_id
-    && def.signature.outputs = []
+    && def.signature.outputs = [ return_ty ]
   then None
   else Some def
 
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