delete more default constructors

reduces code size by 0.1%

src/muz/base/dl_util.cpp

@@ -393,8 +393,6 @@ namespace datalog {
 
     class skip_model_converter : public model_converter {
     public:
-        skip_model_converter() {}
- 
         model_converter * translate(ast_translation & translator) override { 
             return alloc(skip_model_converter);
         }

src/muz/fp/dl_cmds.cpp

@@ -56,8 +56,7 @@ struct dl_context {
         m_cmd(ctx),
         m_collected_cmds(collected_cmds),
         m_ref_count(0),
-        m_decl_plugin(nullptr),
-        m_trail() {}
+        m_decl_plugin(nullptr) {}
 
     void inc_ref() {
         ++m_ref_count;

src/muz/rel/dl_mk_simple_joins.cpp

@@ -54,8 +54,6 @@ namespace datalog {
             var_idx_set m_all_nonlocal_vars;
             rule_vector m_rules;
 
-            pair_info() {}
-
             pair_info & operator=(const pair_info &) = delete;
             bool can_be_joined() const {
                 return m_consumers > 0;

src/muz/rel/dl_relation_manager.cpp

@@ -1043,7 +1043,6 @@ namespace datalog {
     class relation_manager::null_signature_table_project_fn : public table_transformer_fn {
         const table_signature m_empty_sig;
     public:
-        null_signature_table_project_fn() : m_empty_sig() {}
         table_base * operator()(const table_base & t) override {
             relation_manager & m = t.get_plugin().get_manager();
             table_base * res = m.mk_empty_table(m_empty_sig);

src/muz/rel/dl_sieve_relation.h

@@ -36,7 +36,7 @@ namespace datalog {
             /**
                Create uninitialized rel_spec.
             */
-            rel_spec() {} 
+            rel_spec() = default; 
             /**
                \c inner_kind==null_family_id means we will not specify a relation kind when requesting
                the relation object from the relation_manager.

src/muz/rel/karr_relation.cpp

@@ -674,8 +674,6 @@ namespace datalog {
 
     class karr_relation_plugin::union_fn : public relation_union_fn {
     public:
-        union_fn() {}
-
         void operator()(relation_base & _r, const relation_base & _src, relation_base * _delta) override {
 
             karr_relation& r = get(_r);

src/muz/rel/udoc_relation.cpp

@@ -491,8 +491,6 @@ namespace datalog {
     }
     class udoc_plugin::union_fn : public relation_union_fn {
     public:
-        union_fn() {}
-
         void operator()(relation_base & _r, const relation_base & _src, relation_base * _delta) override {
             TRACE("doc", _r.display(tout << "dst:\n"); _src.display(tout  << "src:\n"););
             udoc_relation& r = get(_r);
@@ -1040,8 +1038,6 @@ namespace datalog {
 
     class udoc_plugin::join_project_and_fn : public relation_join_fn {
     public:
-      join_project_and_fn() {}
-
       relation_base* operator()(relation_base const& t1, relation_base const& t2) override {
           udoc_relation *result = get(t1.clone());
           result->get_udoc().intersect(result->get_dm(), get(t2).get_udoc());

src/muz/spacer/spacer_arith_kernel.cpp

@@ -45,8 +45,6 @@ bool spacer_arith_kernel::compute_kernel() {
 namespace {
 class simplex_arith_kernel_plugin : public spacer_arith_kernel::plugin {
   public:
-    simplex_arith_kernel_plugin() {}
-
     bool compute_kernel(const spacer_matrix &in, spacer_matrix &out,
                         vector<unsigned> &basics) override {
         using qmatrix = simplex::sparse_matrix<simplex::mpq_ext>;

src/muz/transforms/dl_mk_magic_sets.h

@@ -65,7 +65,7 @@ namespace datalog {
             func_decl * m_pred;
             adornment m_adornment;
 
-            adornment_desc() {}
+            adornment_desc() = default;
             adornment_desc(func_decl * pred) : m_pred(pred) {}
             adornment_desc(func_decl * pred, const adornment & a) 
                 : m_pred(pred), m_adornment(a) {}