Use = default for virtual constructors.

src/qe/mbp/mbp_plugin.h

@@ -59,7 +59,7 @@ namespace mbp {
 
     public:
         project_plugin(ast_manager& m) :m(m), m_cache(m), m_args(m), m_pure_eqs(m) {}
-        virtual ~project_plugin() {}
+        virtual ~project_plugin() = default;
         virtual bool operator()(model& model, app* var, app_ref_vector& vars, expr_ref_vector& lits) { return false; }
         /**
            \brief partial solver.

src/qe/mbp/mbp_solve_plugin.h

@@ -36,7 +36,7 @@ namespace mbp {
         bool is_variable(expr* e) const { return m_is_var(e); }
     public:
         solve_plugin(ast_manager& m, family_id fid, is_variable_proc& is_var) : m(m), m_id(fid), m_is_var(is_var) {}
-        virtual ~solve_plugin() {}
+        virtual ~solve_plugin() = default;
         family_id get_family_id() const { return m_id; }
         /// Process (and potentially augment) a literal
         expr_ref operator() (expr *lit);

src/qe/nlarith_util.h

@@ -116,7 +116,7 @@ namespace nlarith {
 
         class eval {
         public:
-            virtual ~eval() {}
+            virtual ~eval() = default;
             virtual lbool operator()(app* a) = 0;
         };
 
@@ -124,7 +124,7 @@ namespace nlarith {
         
         class branch {
         public:
-            virtual ~branch() {}
+            virtual ~branch() = default;
             virtual app* get_constraint() = 0;
             virtual void get_updates(ptr_vector<app>& atoms, svector<atom_update>& updates) = 0;
         };

src/qe/qe.cpp

@@ -877,7 +877,7 @@ namespace qe {
 
     class quant_elim {
     public:
-        virtual ~quant_elim() {}
+        virtual ~quant_elim() = default;
     
         virtual lbool eliminate_exists(
             unsigned num_vars, app* const* vars, 

src/qe/qe.h

@@ -149,7 +149,7 @@ namespace qe {
             m_ctx(ctx)
         {}
         
-        virtual ~qe_solver_plugin() {}
+        virtual ~qe_solver_plugin() = default;
         
         family_id get_family_id() { return m_fid; }
 

src/qe/qe_mbi.h

@@ -43,7 +43,7 @@ namespace qe {
         lbool is_shared_cached(expr* e);
     public:
         mbi_plugin(ast_manager& m): m(m), m_shared_trail(m) {}
-        virtual ~mbi_plugin() {}
+        virtual ~mbi_plugin() = default;
 
         /**
          * Set the shared symbols.