Add [[nodiscard]] to AST factory functions and modernize iterator loops (#8143)

* Initial plan

* Add [[nodiscard]] to AST factory functions and modernize iterator loops

- Added [[nodiscard]] attribute to key factory functions in ast.h:
  - All mk_app() variants for creating application nodes
  - All mk_func_decl() variants for creating function declarations
  - All mk_const() variants for creating constants
  - All mk_sort() variants for creating sorts
  - mk_var() for creating variables
  - mk_quantifier(), mk_forall(), mk_exists(), mk_lambda() for quantifiers
  - mk_label(), mk_pattern() and related functions

- Converted iterator loops to range-based for loops in:
  - src/util/region.cpp: pop_scope()
  - src/util/dec_ref_util.h: dec_ref_key_values(), dec_ref_keys(), dec_ref_values()
  - src/util/mpf.h: dispose()
  - src/util/numeral_buffer.h: reset()

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

* Modernize additional iterator loops to range-based for loops

- Converted iterator loops to range-based for loops in:
  - src/api/api_ast_map.cpp: Z3_ast_map_keys() and Z3_ast_map_to_string()
  - src/api/c++/z3++.h: optimize copy constructor and add() method
  - src/opt/wmax.cpp: mk_assumptions()

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

* Revert changes to z3++.h for C++ version compatibility

Revert the range-based for loop changes in src/api/c++/z3++.h to maintain
compatibility with older C++ versions that users may rely on. The C++ API
wrapper must support down-level C++ standards for backward compatibility.

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

* Trigger CI build

[skip ci] is not used to ensure CI runs

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

src/util/dec_ref_util.h

@@ -25,11 +25,9 @@ Notes:
 */
 template<typename Mng, typename Map>
 void dec_ref_key_values(Mng & m, Map & map) {
-    typename Map::iterator it  = map.begin();
-    typename Map::iterator end = map.end();
-    for (; it != end; ++it) {
-        m.dec_ref(it->m_key);
-        m.dec_ref(it->m_value);
+    for (auto& kv : map) {
+        m.dec_ref(kv.m_key);
+        m.dec_ref(kv.m_value);
     }
     map.reset();
 }
@@ -40,10 +38,8 @@ void dec_ref_key_values(Mng & m, Map & map) {
 */
 template<typename Mng, typename Map>
 void dec_ref_keys(Mng & m, Map & map) {
-    typename Map::iterator it  = map.begin();
-    typename Map::iterator end = map.end();
-    for (; it != end; ++it) {
-        m.dec_ref(it->m_key);
+    for (auto& kv : map) {
+        m.dec_ref(kv.m_key);
     }
     map.reset();
 }
@@ -55,10 +51,8 @@ void dec_ref_keys(Mng & m, Map & map) {
 */
 template<typename Mng, typename Map>
 void dec_ref_values(Mng & m, Map & map) {
-    typename Map::iterator it  = map.begin();
-    typename Map::iterator end = map.end();
-    for (; it != end; ++it) {
-        m.dec_ref(it->m_value);
+    for (auto& kv : map) {
+        m.dec_ref(kv.m_value);
     }
     map.reset();
 }

src/util/mpf.h

@@ -247,9 +247,9 @@ protected:
         }
 
         void dispose(u_map<mpz*> & map) {
-            for (u_map<mpz*>::iterator it = map.begin(); it != map.end(); it++) {
-                m.del(*it->m_value);
-                dealloc(it->m_value);
+            for (auto& kv : map) {
+                m.del(*kv.m_value);
+                dealloc(kv.m_value);
             }
         }
 

src/util/numeral_buffer.h

@@ -68,10 +68,8 @@ public:
     }
 
     void reset() {
-        typename vector<Numeral>::iterator it  = m_buffer.begin();
-        typename vector<Numeral>::iterator end = m_buffer.end();
-        for (; it != end; ++it)
-            m().del(*it);
+        for (auto& numeral : m_buffer)
+            m().del(numeral);
         m_buffer.reset();
     }
 

src/util/region.cpp

@@ -40,9 +40,7 @@ void region::reset() {
 void region::pop_scope() {
     unsigned old_size = m_scopes.back();
     m_scopes.pop_back();
-    ptr_vector<char>::iterator it  = m_chunks.begin() + old_size;
-    ptr_vector<char>::iterator end = m_chunks.end();
-    for (; it != end; ++it) 
+    for (auto it = m_chunks.begin() + old_size; it != m_chunks.end(); ++it) 
         dealloc_svect(*it);    
     m_chunks.shrink(old_size);
 }