From 8d5065d35d310b0b2e1d1950797c983df4f4f8a4 Mon Sep 17 00:00:00 2001
From: Murphy Berzish <murphy.berzish@gmail.com>
Date: Wed, 24 Jan 2018 22:02:00 -0500
Subject: [PATCH] fix constant eqc bug in mk_concat

---
 src/smt/theory_str.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/smt/theory_str.cpp b/src/smt/theory_str.cpp
index 680500229..a9eac7dd4 100644
--- a/src/smt/theory_str.cpp
+++ b/src/smt/theory_str.cpp
@@ -709,6 +709,12 @@ namespace smt {
         bool n2HasEqcValue = false;
         expr * v1 = get_eqc_value(n1, n1HasEqcValue);
         expr * v2 = get_eqc_value(n2, n2HasEqcValue);
+        if (u.str.is_string(v1)) {
+            n1HasEqcValue = true;
+        }
+        if (u.str.is_string(v2)) {
+            n2HasEqcValue = true;
+        }
         if (n1HasEqcValue && n2HasEqcValue) {
             zstring n1_str;
             u.str.is_string(v1, n1_str);