diff --git a/src/ast/euf/ho_matcher.cpp b/src/ast/euf/ho_matcher.cpp
index 696f868b2..f86d82b64 100644
--- a/src/ast/euf/ho_matcher.cpp
+++ b/src/ast/euf/ho_matcher.cpp
@@ -727,7 +727,7 @@ namespace euf {
         m_hopat2pat.insert(p1, p);
         m_q2hoq.insert(q, q1);
         m_hoq2q.insert(q1, q);
-        m_hopat2free_vars.insert(p1, free_vars);
+        m_hopat2free_vars.insert(p1, std::move(free_vars));
         m_ho_patterns.push_back(p1);
         m_ho_qs.push_back(q1);
         trail().push(push_back_vector(m_ho_patterns));
diff --git a/src/ast/polymorphism_inst.cpp b/src/ast/polymorphism_inst.cpp
index aa9b1e5fe..be91c8f5e 100644
--- a/src/ast/polymorphism_inst.cpp
+++ b/src/ast/polymorphism_inst.cpp
@@ -123,7 +123,7 @@ namespace polymorphism {
                 expr_ref e_inst = new_sub(e);
                 if (!m_from_instantiation.contains(e_inst)) {
                     collect_instantiations(e_inst);
-                    auto* new_sub1 = alloc(substitution, new_sub);
+                    auto* new_sub1 = alloc(substitution, std::move(new_sub));
                     instances.push_back(instantiation(e, e_inst, new_sub1));
                     new_substs.insert(new_sub1);
                     m_from_instantiation.insert(e_inst);
diff --git a/src/math/polynomial/polynomial.cpp b/src/math/polynomial/polynomial.cpp
index dde532107..f4cfa1fbd 100644
--- a/src/math/polynomial/polynomial.cpp
+++ b/src/math/polynomial/polynomial.cpp
@@ -2133,7 +2133,7 @@ namespace polynomial {
                     m_m2pos.reset(m);
                     m_m2pos.set(m, i);
                 }
-                m_tmp_as.swap(new_as);
+                m_tmp_as = std::move(new_as);
             }
 
             // For each monomial m
diff --git a/src/math/polynomial/upolynomial.cpp b/src/math/polynomial/upolynomial.cpp
index 27478bdf0..2cf2a7b4e 100644
--- a/src/math/polynomial/upolynomial.cpp
+++ b/src/math/polynomial/upolynomial.cpp
@@ -301,7 +301,6 @@ namespace upolynomial {
 
     void core_manager::sub(unsigned sz1, numeral const * p1, unsigned sz2, numeral const * p2, numeral_vector & buffer) {
         sub_core(sz1, p1, sz2, p2, m_basic_tmp);
-        // buffer = std::move(m_basic_tmp);
         buffer.swap(m_basic_tmp);
     }
 
@@ -343,7 +342,6 @@ namespace upolynomial {
 
     void core_manager::mul(unsigned sz1, numeral const * p1, unsigned sz2, numeral const * p2, numeral_vector & buffer) {
         mul_core(sz1, p1, sz2, p2, m_basic_tmp);
-        // buffer = std::move(m_basic_tmp);
         buffer.swap(m_basic_tmp);
     }
 
diff --git a/src/muz/rel/dl_compiler.cpp b/src/muz/rel/dl_compiler.cpp
index f9f7f2060..320d0a206 100644
--- a/src/muz/rel/dl_compiler.cpp
+++ b/src/muz/rel/dl_compiler.cpp
@@ -1145,7 +1145,7 @@ namespace datalog {
         set_difference(local_deltas, global_deltas);
         */
         func_decl_set local_deltas;
-        func_decl_set global_deltas(head_preds);
+        const func_decl_set & global_deltas = head_preds;
 
         pred2idx d_global_src;  //these deltas serve as sources of tuples for rule evaluation inside the loop
         get_fresh_registers(global_deltas, d_global_src);
diff --git a/src/muz/rel/dl_mk_explanations.cpp b/src/muz/rel/dl_mk_explanations.cpp
index d205ddc58..9565a7143 100644
--- a/src/muz/rel/dl_mk_explanations.cpp
+++ b/src/muz/rel/dl_mk_explanations.cpp
@@ -837,8 +837,8 @@ namespace datalog {
             SASSERT(&expl_singleton->get_plugin()==m_er_plugin);
             m_e_fact_relation = static_cast<explanation_relation *>(expl_singleton);
         }
-        func_decl_set predicates(m_context.get_predicates());
-        for (func_decl* orig_decl : predicates) {
+
+        for (func_decl* orig_decl : m_context.get_predicates()) {
             TRACE(dl, tout << mk_pp(orig_decl, m_manager) << "\n";);
             func_decl * e_decl = get_e_decl(orig_decl);
 
diff --git a/src/nlsat/nlsat_scoped_literal_vector.h b/src/nlsat/nlsat_scoped_literal_vector.h
index 4c99e38f7..d67805c15 100644
--- a/src/nlsat/nlsat_scoped_literal_vector.h
+++ b/src/nlsat/nlsat_scoped_literal_vector.h
@@ -29,16 +29,14 @@ namespace nlsat {
     public:
         scoped_literal_vector(solver & s):m_solver(s) {}
         ~scoped_literal_vector() { reset(); }
-        
+
         scoped_literal_vector(scoped_literal_vector && other) noexcept = default;
-        
-        // Move assignment operator
+
         scoped_literal_vector & operator=(scoped_literal_vector && other) noexcept {
             if (this != &other) {
                 SASSERT(&m_solver == &other.m_solver);
                 reset();  // dec_ref our current literals
-                m_lits = std::move(other.m_lits);  // take ownership of other's literals
-                // other.m_lits is now empty
+                m_lits = std::move(other.m_lits);
             }
             return *this;
         }
diff --git a/src/qe/nlqsat.cpp b/src/qe/nlqsat.cpp
index 1761af08b..263dad43c 100644
--- a/src/qe/nlqsat.cpp
+++ b/src/qe/nlqsat.cpp
@@ -385,10 +385,9 @@ namespace qe {
             // They are sorted by size, so we project the largest variables first to avoid 
             // renaming variables. 
             for (unsigned i = vars.size(); i-- > 0;) {
-                new_result.reset();
                 ex.project(vars[i], result.size(), result.data(), new_result);
                 TRACE(qe, display_project(tout, vars[i], result, new_result););
-                result.swap(new_result);
+                result = std::move(new_result);
             }
             negate_clause(result);
         }
diff --git a/src/sat/smt/arith_theory_checker.h b/src/sat/smt/arith_theory_checker.h
index 87868d940..4e84d37c8 100644
--- a/src/sat/smt/arith_theory_checker.h
+++ b/src/sat/smt/arith_theory_checker.h
@@ -358,7 +358,7 @@ namespace arith {
                     continue;                
                 m_ineqs_that_are_eqs.insert(j);
                 if (j < orig_size) {
-                    m_eqs.push_back(m_ineqs[j]);
+                    m_eqs.push_back(std::move(m_ineqs[j]));
                 }
                 else {
                     auto [a, b] = m_deps[j];
diff --git a/src/smt/proto_model/proto_model.cpp b/src/smt/proto_model/proto_model.cpp
index 2d97c4522..a62e51603 100644
--- a/src/smt/proto_model/proto_model.cpp
+++ b/src/smt/proto_model/proto_model.cpp
@@ -239,7 +239,7 @@ void proto_model::cleanup() {
                 unregister_decl(faux);
             }
         }
-        m_aux_decls.swap(found_aux_fs);
+        m_aux_decls = std::move(found_aux_fs);
     }
     TRACE(model_bug, model_v2_pp(tout, *this););
 }
diff --git a/src/solver/mus.cpp b/src/solver/mus.cpp
index 154d72ab6..b225e5379 100644
--- a/src/solver/mus.cpp
+++ b/src/solver/mus.cpp
@@ -201,7 +201,7 @@ struct mus::imp {
                 }
                 if (!min_core_valid || core.size() < min_core.size()) {
                     // The current core is smallest so far, so we get fewer unknowns from it.
-                    min_core = core;
+                    min_core = std::move(core);
                     min_core_valid = true;
                     min_lit = lit;
                 }
diff --git a/src/util/obj_hashtable.h b/src/util/obj_hashtable.h
index ae53fbe6d..329f1aa1e 100644
--- a/src/util/obj_hashtable.h
+++ b/src/util/obj_hashtable.h
@@ -29,13 +29,13 @@ Revision History:
 */
 template<typename T>
 class obj_hash_entry {
-    T *             m_ptr = nullptr;
+    T * m_ptr = nullptr;
 public:
     typedef T * data;
     unsigned get_hash() const { return m_ptr->hash(); }
     bool is_free() const { return m_ptr == nullptr; }
     bool is_deleted() const { return m_ptr == reinterpret_cast<T *>(1); }
-    bool is_used() const { return m_ptr != reinterpret_cast<T *>(0) && m_ptr != reinterpret_cast<T *>(1); }
+    bool is_used() const { return m_ptr != nullptr && m_ptr != reinterpret_cast<T *>(1); }
     T * get_data() const { return m_ptr; }
     T * & get_data() { return m_ptr; }
     void set_data(T * d) { m_ptr = d; }
@@ -50,21 +50,18 @@ public:
     obj_hashtable(unsigned initial_capacity = DEFAULT_HASHTABLE_INITIAL_CAPACITY):
         core_hashtable<obj_hash_entry<T>, obj_ptr_hash<T>, ptr_eq<T> >(initial_capacity) {}
 
+    obj_hashtable(const obj_hashtable & source) = default;
+    obj_hashtable(obj_hashtable && source) noexcept = default;
+    obj_hashtable& operator=(const obj_hashtable & other) = delete;
+    obj_hashtable& operator=(obj_hashtable && other) noexcept = default;
 };
 
 template<typename Key, typename Value>
 class obj_map {
 public:
     struct key_data {
-        Key *  m_key = nullptr;
-        Value  m_value;
-        key_data() {}
-        key_data(Key *key) : m_key(key) {}
-        key_data(Key *k, Value const &v) : m_key(k), m_value(v) {}
-        key_data(key_data &&kd) noexcept = default;
-        key_data(key_data const &kd) noexcept = default;
-        key_data &operator=(key_data const &kd)  = default;
-        key_data &operator=(key_data &&kd) = default;
+        Key * m_key = nullptr;
+        Value m_value;
         Value const & get_value() const { return m_value; }
         Key & get_key () const { return *m_key; }
         unsigned hash() const { return m_key->hash(); }
@@ -94,7 +91,12 @@ public:
 public:
     obj_map(unsigned initial_capacity = DEFAULT_HASHTABLE_INITIAL_CAPACITY):
         m_table(initial_capacity) {}
-    
+
+    obj_map(const obj_map & source) = default;
+    obj_map(obj_map && source) noexcept = default;
+    obj_map& operator=(const obj_map & other) = delete;
+    obj_map& operator=(obj_map && other) noexcept = default;
+
     typedef typename table::iterator iterator;
     typedef typename table::data data;
     typedef typename table::entry entry;
@@ -141,16 +143,22 @@ public:
         return m_table.insert_if_not_there2(key_data(k, v))->get_data().m_value;
     }
 
+    Value& insert_if_not_there(Key * k, Value && v) {
+        obj_map_entry * e = nullptr;
+        m_table.insert_if_not_there_core({k, std::move(v)}, e);
+        return e->get_data().m_value;
+    }
+
     bool insert_if_not_there_core(Key * k, Value const & v, obj_map_entry * & et) {
         return m_table.insert_if_not_there_core({k, v}, et);
     }
 
     obj_map_entry * insert_if_not_there3(Key * k, Value const & v) {
-        return m_table.insert_if_not_there2(key_data(k, v));
+        return m_table.insert_if_not_there2({k, v});
     }
     
     obj_map_entry * find_core(Key * k) const {
-        return m_table.find_core(key_data(k));
+        return m_table.find_core({k});
     }
 
     bool find(Key * const k, Value & v) const {
diff --git a/src/util/s_integer.cpp b/src/util/s_integer.cpp
index 53d19270b..848dd2901 100644
--- a/src/util/s_integer.cpp
+++ b/src/util/s_integer.cpp
@@ -19,10 +19,6 @@ Revision History:
 
 #include "util/s_integer.h"
 
-s_integer s_integer::m_zero(0);
-s_integer s_integer::m_one(1);
-s_integer s_integer::m_minus_one(-1);
-
 s_integer::s_integer(const char * str) {
     m_val = static_cast<int>(strtol(str, nullptr, 10));
 }
diff --git a/src/util/s_integer.h b/src/util/s_integer.h
index 5accf7b4b..e08439d23 100644
--- a/src/util/s_integer.h
+++ b/src/util/s_integer.h
@@ -22,9 +22,6 @@ Revision History:
 
 class s_integer {
     int m_val = 0;
-    static s_integer m_zero;
-    static s_integer m_one;
-    static s_integer m_minus_one;
 public:
 
     unsigned hash() const { 
@@ -39,10 +36,6 @@ public:
 public:
     s_integer() = default;
     explicit s_integer(int n):m_val(n) {}
-    struct i64 {};
-    explicit s_integer(int64_t i, i64):m_val(static_cast<int>(i)) {}
-    struct ui64 {};
-    explicit s_integer(uint64_t i, ui64):m_val(static_cast<int>(i)) {}
     explicit s_integer(const char * str);
     explicit s_integer(const rational & r):m_val(static_cast<int>(r.get_int64())) {}
 
@@ -58,12 +51,12 @@ public:
     uint64_t get_uint64() const { return m_val; }
     static bool is_unsigned() { return true; }
     unsigned get_unsigned() const { return static_cast<unsigned>(m_val); }
-    s_integer const& get_s_integer() const { return *this; }
-    s_integer const& get_infinitesimal() const { return zero(); }
+    s_integer get_s_integer() const { return *this; }
+    s_integer get_infinitesimal() const { return s_integer(0); }
     static bool is_rational() { return true; }
     s_integer const& get_rational() const { return *this; } 
     friend inline s_integer numerator(const s_integer & r) { return r; }
-    friend inline s_integer denominator(const s_integer & r) { return one(); }
+    friend inline s_integer denominator(const s_integer & r) { return s_integer(1); }
     s_integer & operator+=(const s_integer & r) { m_val += r.m_val; return *this; }
     s_integer & operator-=(const s_integer & r) { m_val -= r.m_val; return *this; }
     s_integer & operator*=(const s_integer & r) { m_val *= r.m_val; return *this; }
@@ -103,9 +96,6 @@ public:
         return result;
     }
 
-    static const s_integer & zero() { return m_zero; }
-    static const s_integer & one() { return m_one; }
-    static const s_integer & minus_one() { return m_minus_one; }
     // Perform:  this += c * k
     void addmul(const s_integer & c, const s_integer & k) { m_val += c.m_val * k.m_val; }
     void submul(const s_integer & c, const s_integer & k) { m_val -= c.m_val * k.m_val; }
@@ -137,5 +127,3 @@ inline s_integer abs(const s_integer & r) {
     }
     return result;
 }
-
-