From e6ea81546eb78b6ad1e5920954796f6d1c2074e4 Mon Sep 17 00:00:00 2001
From: Nikolaj Bjorner <nbjorner@microsoft.com>
Date: Sat, 8 Apr 2023 17:14:39 -0700
Subject: [PATCH] fix #6662

---
 src/ast/special_relations_decl_plugin.cpp |  1 +
 src/ast/special_relations_decl_plugin.h   |  5 +++++
 src/smt/smt_model_checker.cpp             | 23 ++++++++++++++++++++++-
 src/smt/smt_model_checker.h               |  1 +
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/ast/special_relations_decl_plugin.cpp b/src/ast/special_relations_decl_plugin.cpp
index b45778d2f83..24a756bf79e 100644
--- a/src/ast/special_relations_decl_plugin.cpp
+++ b/src/ast/special_relations_decl_plugin.cpp
@@ -47,6 +47,7 @@ func_decl * special_relations_decl_plugin::mk_func_decl(
     if (!m_manager->is_bool(range)) {
         m_manager->raise_exception("range type is expected to be Boolean for special relations");
     }
+    m_has_special_relation = true;
     func_decl_info info(m_family_id, k, num_parameters, parameters);
     symbol name;
     switch(k) {
diff --git a/src/ast/special_relations_decl_plugin.h b/src/ast/special_relations_decl_plugin.h
index 0c437786421..c422cbcdc01 100644
--- a/src/ast/special_relations_decl_plugin.h
+++ b/src/ast/special_relations_decl_plugin.h
@@ -37,6 +37,7 @@ class special_relations_decl_plugin : public decl_plugin {
     symbol m_plo;
     symbol m_to;
     symbol m_tc;
+    bool   m_has_special_relation = false;
 public:
     special_relations_decl_plugin();
 
@@ -50,6 +51,8 @@ class special_relations_decl_plugin : public decl_plugin {
     void get_op_names(svector<builtin_name> & op_names, symbol const & logic) override;
     
     sort * mk_sort(decl_kind k, unsigned num_parameters, parameter const * parameters) override { return nullptr; }
+
+    bool has_special_relation() const { return m_has_special_relation; }
 };
 
 enum sr_property {
@@ -82,6 +85,8 @@ class special_relations_util {
     }
 public:
     special_relations_util(ast_manager& m) : m(m), m_fid(null_family_id) { }
+
+    bool has_special_relation() const { return static_cast<special_relations_decl_plugin*>(m.get_plugin(m.mk_family_id("specrels")))->has_special_relation(); }
     
     bool is_special_relation(func_decl* f) const { return f->get_family_id() == fid(); }
     bool is_special_relation(app* e) const { return is_special_relation(e->get_decl()); }
diff --git a/src/smt/smt_model_checker.cpp b/src/smt/smt_model_checker.cpp
index e555088538c..2d23504945a 100644
--- a/src/smt/smt_model_checker.cpp
+++ b/src/smt/smt_model_checker.cpp
@@ -28,6 +28,7 @@ Revision History:
 #include "ast/rewriter/rewriter_def.h"
 #include "ast/ast_pp.h"
 #include "ast/array_decl_plugin.h"
+#include "ast/special_relations_decl_plugin.h"
 #include "ast/ast_smt2_pp.h"
 #include "smt/smt_model_checker.h"
 #include "smt/smt_context.h"
@@ -358,7 +359,7 @@ namespace smt {
         
         TRACE("model_checker", tout << "[complete] model-checker result: " << to_sat_str(r) << "\n";);
         if (r != l_true) {
-            return r == l_false; // quantifier is satisfied by m_curr_model
+            return is_safe_for_mbqi(q) && r == l_false; // quantifier is satisfied by m_curr_model
         }
 
         model_ref complete_cex;
@@ -398,6 +399,26 @@ namespace smt {
         return false;
     }
 
+    bool model_checker::is_safe_for_mbqi(quantifier * q) const {
+        special_relations_util sp(m);
+        if (!sp.has_special_relation())
+            return true;
+        ast_fast_mark1 visited;
+        struct proc {
+            special_relations_util& sp;
+            bool found = false;
+            proc(special_relations_util& sp):sp(sp) {}
+            void operator()(app* f) {
+                found |= sp.is_special_relation(f);
+            }
+            void operator()(expr* e) {}
+        };
+        proc p(sp);
+        quick_for_each_expr(p, visited, q);
+        return !p.found;
+    }
+
+
     void model_checker::init_aux_context() {
         if (!m_fparams) {
             m_fparams = alloc(smt_params, m_context->get_fparams());
diff --git a/src/smt/smt_model_checker.h b/src/smt/smt_model_checker.h
index 6332a890e83..46d51f9a015 100644
--- a/src/smt/smt_model_checker.h
+++ b/src/smt/smt_model_checker.h
@@ -87,6 +87,7 @@ namespace smt {
         expr_mark m_visited;
         bool contains_model_value(expr * e);
         void add_instance(quantifier * q, expr_ref_vector const & bindings, unsigned max_generation, expr * def);
+        bool is_safe_for_mbqi(quantifier * q) const;
 
     public:
         model_checker(ast_manager & m, qi_params const & p, model_finder & mf);