Check only a pointer can be dereferenced

include/elna/boot/ast.h

@@ -156,7 +156,36 @@ namespace elna::boot
         virtual defer_statement *is_defer();
         virtual procedure_call *is_call_statement();
 
-        void accept(parser_visitor *visitor);
+        template<typename V>
+        void accept(V *visitor)
+        {
+            if (assign_statement *node = is_assign())
+            {
+                return visitor->visit(node);
+            }
+            else if (if_statement *node = is_if())
+            {
+                return visitor->visit(node);
+            }
+            else if (while_statement *node = is_while())
+            {
+                return visitor->visit(node);
+            }
+            else if (return_statement *node = is_return())
+            {
+                return visitor->visit(node);
+            }
+            else if (defer_statement *node = is_defer())
+            {
+                return visitor->visit(node);
+            }
+            else if (procedure_call *node = is_call_statement())
+            {
+                return visitor->visit(node);
+            }
+            __builtin_unreachable();
+        }
+
         ~statement() = 0;
 
     protected:
@@ -739,7 +768,8 @@ namespace elna::boot
             }
         }
 
-        void accept(parser_visitor *visitor)
+        template<typename V>
+        void accept(V *visitor)
         {
             visitor->visit(this);
         }