From bcee5ef4d425033b163970d15ec9e19c6fbb7e91 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 12 Jul 2026 23:49:22 +0000
Subject: [PATCH] Add regression test for QE unsoundness issue #4175

---
 src/test/quant_solve.cpp | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/src/test/quant_solve.cpp b/src/test/quant_solve.cpp
index 28667917fc..8bf0818a30 100644
--- a/src/test/quant_solve.cpp
+++ b/src/test/quant_solve.cpp
@@ -168,6 +168,44 @@ static void test_quant_solver(ast_manager& m, char const* str, bool validate = t
     test_quant_solver(m, vars.size(), vars.data(), fml, validate);
 }
 
+static void test_qe_regression_4175() {
+    ast_manager m;
+    reg_decl_plugins(m);
+    smt_params params;
+    arith_util a(m);
+
+    expr_ref fml = parse_fml(m, "(forall ((b Real)) (= (= r1 b) (= b 0)))");
+    expr_ref result(m);
+    qe::expr_quant_elim qe(m, params);
+    qe(m.mk_true(), fml, result);
+
+    expr_ref r1(m.mk_const(symbol("r1"), a.mk_real()), m);
+    expr_ref zero(a.mk_numeral(rational(0), false), m);
+
+    {
+        smt::kernel solver(m, params);
+        solver.assert_expr(fml);
+        VERIFY(l_true == solver.check());
+    }
+    {
+        smt::kernel solver(m, params);
+        solver.assert_expr(result);
+        VERIFY(l_true == solver.check());
+    }
+    {
+        smt::kernel solver(m, params);
+        solver.assert_expr(result);
+        solver.assert_expr(m.mk_eq(r1, zero));
+        VERIFY(l_true == solver.check());
+    }
+    {
+        smt::kernel solver(m, params);
+        solver.assert_expr(result);
+        solver.assert_expr(m.mk_not(m.mk_eq(r1, zero)));
+        VERIFY(l_false == solver.check());
+    }
+}
+
 
 static void test_quant_solve1() {
     ast_manager m;
@@ -253,6 +291,7 @@ void tst_quant_solve() {
     disable_debug("heap");
 
     test_quant_solve1();   
+    test_qe_regression_4175();
 
 #if 0
     memory::finalize();
@@ -263,4 +302,3 @@ void tst_quant_solve() {
 #endif
 }
 
-