From 8c02ec087b8fb19d5cc793794e0fad42f8b7283f Mon Sep 17 00:00:00 2001
From: Nikolaj Bjorner <nbjorner@microsoft.com>
Date: Tue, 5 May 2026 10:53:12 -0700
Subject: [PATCH] fix crash with
 D:\\bench\\inputs\\QF_S\\20240318-omark\\cyclic-xy.smt2

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
---
 src/smt/seq/seq_nielsen.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/smt/seq/seq_nielsen.h b/src/smt/seq/seq_nielsen.h
index 303ee8d21..caa1d76da 100644
--- a/src/smt/seq/seq_nielsen.h
+++ b/src/smt/seq/seq_nielsen.h
@@ -640,7 +640,12 @@ namespace seq {
         bool upper_bound(expr* e, rational& up, dep_tracker& dep);
 
         // character constraint access (mirrors ZIPT's CharRanges)
-        u_map<std::pair<char_set, dep_tracker>> char_ranges() const { return m_char_ranges; }
+        u_map<std::pair<char_set, dep_tracker>>& char_ranges() { return m_char_ranges; }
+        u_map<std::pair<char_set, dep_tracker>> const &char_ranges() const {
+            return m_char_ranges;
+        }
+        
+        
 
         // add a character range constraint for a symbolic char.
         // intersects with existing range; sets conflict if result is empty.