diff --git a/src/ast/CMakeLists.txt b/src/ast/CMakeLists.txt
index b0c9f7724..f14a28373 100644
--- a/src/ast/CMakeLists.txt
+++ b/src/ast/CMakeLists.txt
@@ -14,6 +14,7 @@ z3_add_component(ast
     ast_translation.cpp
     ast_util.cpp
     bv_decl_plugin.cpp
+    cached_var_subst.cpp
     char_decl_plugin.cpp
     datatype_decl_plugin.cpp
     decl_collector.cpp
@@ -37,6 +38,7 @@ z3_add_component(ast
     occurs.cpp
     pb_decl_plugin.cpp
     pp.cpp
+    quantifier_stat.cpp
     recfun_decl_plugin.cpp
     reg_decl_plugins.cpp
     seq_decl_plugin.cpp
diff --git a/src/ast/cached_var_subst.cpp b/src/ast/cached_var_subst.cpp
new file mode 100644
index 000000000..93b7467bd
--- /dev/null
+++ b/src/ast/cached_var_subst.cpp
@@ -0,0 +1,99 @@
+/*++
+Copyright (c) 2006 Microsoft Corporation
+
+Module Name:
+
+    cached_var_subst.cpp
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Leonardo de Moura (leonardo) 2009-01-23.
+
+Revision History:
+
+--*/
+#include "ast/cached_var_subst.h"
+#include "ast/rewriter/rewriter_def.h"
+
+bool cached_var_subst::key_eq_proc::operator()(cached_var_subst::key * k1, cached_var_subst::key * k2) const {
+    if (k1->m_qa != k2->m_qa)
+        return false;
+    if (k1->m_num_bindings != k2->m_num_bindings)
+        return false;
+    for (unsigned i = 0; i < k1->m_num_bindings; i++)
+        if (k1->m_bindings[i] != k2->m_bindings[i])
+            return false;
+    return true;
+}
+
+cached_var_subst::cached_var_subst(ast_manager & _m):
+    m(_m),
+    m_proc(m),
+    m_refs(m) {
+}
+
+void cached_var_subst::reset() {
+    m_refs.reset();
+    m_instances.reset();
+    m_region.reset();
+    m_new_keys.reset();
+    m_key = nullptr;
+}
+
+expr** cached_var_subst::operator()(quantifier* qa, unsigned num_bindings) {
+    m_new_keys.reserve(num_bindings+1, 0);
+    m_key = m_new_keys[num_bindings];
+    if (m_key == nullptr)
+        m_key = static_cast<key*>(m_region.allocate(sizeof(key) + sizeof(expr*)*num_bindings));
+    m_key->m_qa           = qa;
+    m_key->m_num_bindings = num_bindings;
+    return m_key->m_bindings;
+}
+
+
+expr_ref cached_var_subst::operator()() {
+    expr_ref result(m);
+
+    auto* entry = m_instances.insert_if_not_there3(m_key, nullptr);
+    unsigned num_bindings = m_key->m_num_bindings;
+    if (entry->get_data().m_key != m_key) {
+        SASSERT(entry->get_data().m_value != 0);
+        // entry was already there
+        m_new_keys[num_bindings] = m_key; // recycle key
+        result = entry->get_data().m_value;
+        SCTRACE("bindings", is_trace_enabled("coming_from_quant"), tout << "(cache)\n";
+                for (unsigned i = 0; i < num_bindings; i++) 
+                    if (m_key->m_bindings[i]) 
+                        tout << i << ": " << mk_ismt2_pp(m_key->m_bindings[i], result.m()) << ";\n";
+                tout.flush(););
+        return result;
+    }
+
+    SASSERT(entry->get_data().m_value == 0);
+    try {
+        result = m_proc(m_key->m_qa->get_expr(), m_key->m_num_bindings, m_key->m_bindings);
+    }
+    catch (...) {
+        // CMW: The var_subst reducer was interrupted and m_instances is
+        // in an inconsistent state; we need to remove (m_key, 0).
+        m_instances.remove(m_key);
+        throw; 
+    }
+
+    // cache result
+    entry->get_data().m_value = result;
+
+    // remove key from cache
+    m_new_keys[num_bindings] = nullptr;
+
+    // increment reference counters
+    m_refs.push_back(m_key->m_qa);
+    for (unsigned i = 0; i < m_key->m_num_bindings; i++)
+        m_refs.push_back(m_key->m_bindings[i]);
+    m_refs.push_back(result);
+    return result;
+}
diff --git a/src/smt/cached_var_subst.h b/src/ast/cached_var_subst.h
similarity index 87%
rename from src/smt/cached_var_subst.h
rename to src/ast/cached_var_subst.h
index 54d462bf2..2675f46ce 100644
--- a/src/smt/cached_var_subst.h
+++ b/src/ast/cached_var_subst.h
@@ -20,7 +20,6 @@ Revision History:
 
 #include "ast/rewriter/var_subst.h"
 #include "util/map.h"
-#include "smt/smt_enode.h"
 
 class cached_var_subst {
     struct key {
@@ -37,14 +36,17 @@ class cached_var_subst {
         bool operator()(key * k1, key * k2) const;
     };
     typedef map<key *, expr *, key_hash_proc, key_eq_proc> instances;
+    ast_manager&     m;
     var_subst        m_proc;
     expr_ref_vector  m_refs;
     instances        m_instances;
     region           m_region;
     ptr_vector<key>  m_new_keys; // mapping from num_bindings -> next key
+    key*             m_key { nullptr };
 public:
     cached_var_subst(ast_manager & m);
-    void operator()(quantifier * qa, unsigned num_bindings, smt::enode * const * bindings, expr_ref & result);
+    expr** operator()(quantifier * qa, unsigned num_bindings);
+    expr_ref operator()();
     void reset();
 };
 
diff --git a/src/smt/smt_quantifier_stat.cpp b/src/ast/quantifier_stat.cpp
similarity index 98%
rename from src/smt/smt_quantifier_stat.cpp
rename to src/ast/quantifier_stat.cpp
index 78c0124c3..17efb11e9 100644
--- a/src/smt/smt_quantifier_stat.cpp
+++ b/src/ast/quantifier_stat.cpp
@@ -16,9 +16,9 @@ Author:
 Revision History:
 
 --*/
-#include "smt/smt_quantifier_stat.h"
+#include "ast/quantifier_stat.h"
 
-namespace smt {
+namespace q {
 
     quantifier_stat::quantifier_stat(unsigned generation):
         m_size(0),
diff --git a/src/smt/smt_quantifier_stat.h b/src/ast/quantifier_stat.h
similarity index 98%
rename from src/smt/smt_quantifier_stat.h
rename to src/ast/quantifier_stat.h
index ffa20cb43..45fd58530 100644
--- a/src/smt/smt_quantifier_stat.h
+++ b/src/ast/quantifier_stat.h
@@ -3,7 +3,7 @@ Copyright (c) 2006 Microsoft Corporation
 
 Module Name:
 
-    smt_quantifier_stat.h
+    quantifier_stat.h
 
 Abstract:
 
@@ -23,7 +23,7 @@ Revision History:
 #include "util/approx_nat.h"
 #include "util/region.h"
 
-namespace smt {
+namespace q {
     
     /**
        \brief Store statistics for quantifiers. This information is
diff --git a/src/smt/CMakeLists.txt b/src/smt/CMakeLists.txt
index 6f414dd78..c9b6988cf 100644
--- a/src/smt/CMakeLists.txt
+++ b/src/smt/CMakeLists.txt
@@ -3,7 +3,6 @@ z3_add_component(smt
     arith_eq_adapter.cpp
     arith_eq_solver.cpp
     asserted_formulas.cpp
-    cached_var_subst.cpp
     cost_evaluator.cpp
     dyn_ack.cpp
     expr_context_simplifier.cpp
@@ -45,7 +44,6 @@ z3_add_component(smt
     smt_model_generator.cpp
     smt_parallel.cpp
     smt_quantifier.cpp
-    smt_quantifier_stat.cpp
     smt_quick_checker.cpp
     smt_relevancy.cpp
     smt_setup.cpp
diff --git a/src/smt/cached_var_subst.cpp b/src/smt/cached_var_subst.cpp
deleted file mode 100644
index b2e3cccd1..000000000
--- a/src/smt/cached_var_subst.cpp
+++ /dev/null
@@ -1,94 +0,0 @@
-/*++
-Copyright (c) 2006 Microsoft Corporation
-
-Module Name:
-
-    cached_var_subst.cpp
-
-Abstract:
-
-    <abstract>
-
-Author:
-
-    Leonardo de Moura (leonardo) 2009-01-23.
-
-Revision History:
-
---*/
-#include "smt/cached_var_subst.h"
-#include "ast/rewriter/rewriter_def.h"
-
-bool cached_var_subst::key_eq_proc::operator()(cached_var_subst::key * k1, cached_var_subst::key * k2) const {
-    if (k1->m_qa != k2->m_qa)
-        return false;
-    if (k1->m_num_bindings != k2->m_num_bindings)
-        return false;
-    for (unsigned i = 0; i < k1->m_num_bindings; i++)
-        if (k1->m_bindings[i] != k2->m_bindings[i])
-            return false;
-    return true;
-}
-
-cached_var_subst::cached_var_subst(ast_manager & m):
-    m_proc(m),
-    m_refs(m) {
-}
-
-void cached_var_subst::reset() {
-    m_refs.reset();
-    m_instances.reset();
-    m_region.reset();
-    m_new_keys.reset();
-}
-
-void cached_var_subst::operator()(quantifier * qa, unsigned num_bindings, smt::enode * const * bindings, expr_ref & result) {
-    m_new_keys.reserve(num_bindings+1, 0);
-    key * new_key = m_new_keys[num_bindings];
-    if (new_key == nullptr)
-        new_key = static_cast<key*>(m_region.allocate(sizeof(key) + sizeof(expr*)*num_bindings));
-
-    new_key->m_qa           = qa;
-    new_key->m_num_bindings = num_bindings;
-    for (unsigned i = 0; i < num_bindings; i++)
-        new_key->m_bindings[i] = bindings[i]->get_owner();
-
-    auto* entry = m_instances.insert_if_not_there3(new_key, nullptr);
-    if (entry->get_data().m_key != new_key) {
-        SASSERT(entry->get_data().m_value != 0);
-        // entry was already there
-        m_new_keys[num_bindings] = new_key; // recycle key
-        result = entry->get_data().m_value;
-        SCTRACE("bindings", is_trace_enabled("coming_from_quant"),tout << "(cache)\n";
-            for (unsigned i = 0; i < num_bindings; i++) {
-                if (new_key->m_bindings[i]) {
-                    tout << i << ": " << mk_ismt2_pp(new_key->m_bindings[i], result.m()) << ";\n";
-                }
-            }
-            tout.flush(););
-        return;
-    }
-
-    SASSERT(entry->get_data().m_value == 0);
-    try {
-        result = m_proc(qa->get_expr(), new_key->m_num_bindings, new_key->m_bindings);
-    }
-    catch (...) {
-        // CMW: The var_subst reducer was interrupted and m_instances is
-        // in an inconsistent state; we need to remove (new_key, 0).
-        m_instances.remove(new_key);
-        throw; // Throw on to smt::qi_queue/smt::solver.
-    }
-
-    // cache result
-    entry->get_data().m_value = result;
-
-    // remove key from cache
-    m_new_keys[num_bindings] = 0;
-
-    // increment reference counters
-    m_refs.push_back(qa);
-    for (unsigned i = 0; i < new_key->m_num_bindings; i++)
-        m_refs.push_back(new_key->m_bindings[i]);
-    m_refs.push_back(result);
-}
diff --git a/src/smt/qi_queue.cpp b/src/smt/qi_queue.cpp
index 8cc9429a8..a7b03dc3e 100644
--- a/src/smt/qi_queue.cpp
+++ b/src/smt/qi_queue.cpp
@@ -98,8 +98,8 @@ namespace smt {
         m_parser.add_var("cs_factor");
     }
 
-    quantifier_stat * qi_queue::set_values(quantifier * q, app * pat, unsigned generation, unsigned min_top_generation, unsigned max_top_generation, float cost) {
-        quantifier_stat * stat     = m_qm.get_stat(q);
+    q::quantifier_stat * qi_queue::set_values(quantifier * q, app * pat, unsigned generation, unsigned min_top_generation, unsigned max_top_generation, float cost) {
+        q::quantifier_stat * stat     = m_qm.get_stat(q);
         m_vals[COST]               = cost;
         m_vals[MIN_TOP_GENERATION] = static_cast<float>(min_top_generation);
         m_vals[MAX_TOP_GENERATION] = static_cast<float>(max_top_generation);
@@ -120,7 +120,7 @@ namespace smt {
     }
 
     float qi_queue::get_cost(quantifier * q, app * pat, unsigned generation, unsigned min_top_generation, unsigned max_top_generation) {
-        quantifier_stat * stat = set_values(q, pat, generation, min_top_generation, max_top_generation, 0);
+        q::quantifier_stat * stat = set_values(q, pat, generation, min_top_generation, max_top_generation, 0);
         float r = m_evaluator(m_cost_function, m_vals.size(), m_vals.c_ptr());
         stat->update_max_cost(r);
         return r;
@@ -206,7 +206,7 @@ namespace smt {
                 
         TRACE("qi_queue_profile", tout << q->get_qid() << ", gen: " << generation << " " << *f << " cost: " << ent.m_cost << "\n";);
 
-        quantifier_stat * stat = m_qm.get_stat(q);
+        q::quantifier_stat * stat = m_qm.get_stat(q);
 
         if (m_checker.is_sat(q->get_expr(), num_bindings, bindings)) {
             TRACE("checker", tout << "instance already satisfied\n";);
@@ -221,8 +221,10 @@ namespace smt {
 
         STRACE("instance", tout << "### " << static_cast<void*>(f) <<", " << q->get_qid()  << "\n";);
 
-        expr_ref instance(m);
-        m_subst(q, num_bindings, bindings, instance);
+        auto* ebindings = m_subst(q, num_bindings);
+        for (unsigned i = 0; i < num_bindings; ++i)
+            ebindings[i] = bindings[i]->get_owner();
+        expr_ref instance = m_subst();
 
         TRACE("qi_queue", tout << "new instance:\n" << mk_pp(instance, m) << "\n";);
         TRACE("qi_queue_instance", tout << "new instance:\n" << mk_pp(instance, m) << "\n";);
diff --git a/src/smt/qi_queue.h b/src/smt/qi_queue.h
index 50ba2e1b9..7ea524b9e 100644
--- a/src/smt/qi_queue.h
+++ b/src/smt/qi_queue.h
@@ -19,14 +19,14 @@ Revision History:
 #pragma once
 
 #include "ast/ast.h"
-#include "smt/smt_quantifier_stat.h"
+#include "ast/cached_var_subst.h"
+#include "ast/quantifier_stat.h"
 #include "smt/smt_checker.h"
 #include "smt/smt_quantifier.h"
 #include "smt/fingerprints.h"
 #include "smt/params/qi_params.h"
 #include "parsers/util/cost_parser.h"
 #include "smt/cost_evaluator.h"
-#include "smt/cached_var_subst.h"
 #include "util/statistics.h"
 
 namespace smt {
@@ -71,7 +71,7 @@ namespace smt {
         svector<scope>                m_scopes;
 
         void init_parser_vars();
-        quantifier_stat * set_values(quantifier * q, app * pat, unsigned generation, unsigned min_top_generation, unsigned max_top_generation, float cost);
+        q::quantifier_stat * set_values(quantifier * q, app * pat, unsigned generation, unsigned min_top_generation, unsigned max_top_generation, float cost);
         float get_cost(quantifier * q, app * pat, unsigned generation, unsigned min_top_generation, unsigned max_top_generation);
         unsigned get_new_gen(quantifier * q, unsigned generation, float cost);
         void instantiate(entry & ent);
diff --git a/src/smt/smt_context.h b/src/smt/smt_context.h
index 8f08d1607..2a13b29f3 100644
--- a/src/smt/smt_context.h
+++ b/src/smt/smt_context.h
@@ -18,6 +18,7 @@ Revision History:
 --*/
 #pragma once
 
+#include "ast/quantifier_stat.h"
 #include "smt/smt_clause.h"
 #include "smt/smt_setup.h"
 #include "smt/smt_enode.h"
@@ -29,7 +30,6 @@ Revision History:
 #include "smt/smt_clause_proof.h"
 #include "smt/smt_theory.h"
 #include "smt/smt_quantifier.h"
-#include "smt/smt_quantifier_stat.h"
 #include "smt/smt_statistics.h"
 #include "smt/smt_conflict_resolution.h"
 #include "smt/smt_relevancy.h"
diff --git a/src/smt/smt_quantifier.cpp b/src/smt/smt_quantifier.cpp
index 8de933c44..774906d05 100644
--- a/src/smt/smt_quantifier.cpp
+++ b/src/smt/smt_quantifier.cpp
@@ -18,9 +18,9 @@ Revision History:
 --*/
 #include "ast/ast_pp.h"
 #include "ast/ast_ll_pp.h"
+#include "ast/quantifier_stat.h"
 #include "smt/smt_quantifier.h"
 #include "smt/smt_context.h"
-#include "smt/smt_quantifier_stat.h"
 #include "smt/smt_model_finder.h"
 #include "smt/smt_model_checker.h"
 #include "smt/smt_quick_checker.h"
@@ -129,8 +129,8 @@ namespace smt {
         context &                              m_context;
         smt_params &                           m_params;
         qi_queue                               m_qi_queue;
-        obj_map<quantifier, quantifier_stat *> m_quantifier_stat;
-        quantifier_stat_gen                    m_qstat_gen;
+        obj_map<quantifier, q::quantifier_stat *> m_quantifier_stat;
+        q::quantifier_stat_gen                    m_qstat_gen;
         ptr_vector<quantifier>                 m_quantifiers;
         scoped_ptr<quantifier_manager_plugin>  m_plugin;
         unsigned                               m_num_instances;
@@ -150,7 +150,7 @@ namespace smt {
         bool has_trace_stream() const { return m().has_trace_stream(); }
         std::ostream & trace_stream() { return m().trace_stream(); }
 
-        quantifier_stat * get_stat(quantifier * q) const {
+        q::quantifier_stat * get_stat(quantifier * q) const {
             return m_quantifier_stat.find(q);
         }
 
@@ -159,7 +159,7 @@ namespace smt {
         }
 
         void add(quantifier * q, unsigned generation) {
-            quantifier_stat * stat = m_qstat_gen(q, generation);
+            q::quantifier_stat * stat = m_qstat_gen(q, generation);
             m_quantifier_stat.insert(q, stat);
             m_quantifiers.push_back(q);
             m_plugin->add(q);
@@ -168,7 +168,7 @@ namespace smt {
         bool has_quantifiers() const { return !m_quantifiers.empty(); }
 
         void display_stats(std::ostream & out, quantifier * q) {
-            quantifier_stat * s     = get_stat(q);
+            q::quantifier_stat * s     = get_stat(q);
             unsigned num_instances  = s->get_num_instances();
             unsigned num_instances_simplify_true = s->get_num_instances_simplify_true();
             unsigned num_instances_checker_sat  = s->get_num_instances_checker_sat();
@@ -460,7 +460,7 @@ namespace smt {
         return m_imp->is_shared(n);
     }
 
-    quantifier_stat * quantifier_manager::get_stat(quantifier * q) const {
+    q::quantifier_stat * quantifier_manager::get_stat(quantifier * q) const {
         return m_imp->get_stat(q);
     }
 
diff --git a/src/smt/smt_quantifier.h b/src/smt/smt_quantifier.h
index abe84916b..4978797a6 100644
--- a/src/smt/smt_quantifier.h
+++ b/src/smt/smt_quantifier.h
@@ -19,6 +19,7 @@ Revision History:
 #pragma once
 
 #include "ast/ast.h"
+#include "ast/quantifier_stat.h"
 #include "util/statistics.h"
 #include "util/params.h"
 #include "smt/smt_types.h"
@@ -50,7 +51,7 @@ namespace smt {
 
         bool is_shared(enode * n) const;
 
-        quantifier_stat * get_stat(quantifier * q) const;
+        q::quantifier_stat * get_stat(quantifier * q) const;
         unsigned get_generation(quantifier * q) const;
 
         static void log_justification_to_root(std::ostream & log, enode *en, obj_hashtable<enode> &already_visited, context &ctx, ast_manager &m);