Use concepts for push_back detection

include/boost/parser/parser.hpp

@@ -1193,9 +1193,14 @@ namespace boost { namespace parser {
         constexpr bool is_range =
             is_detected_v<has_begin, T> && is_detected_v<has_end, T>;
 
+#if BOOST_PARSER_USE_CONCEPTS
+        template<typename T>
+        concept has_push_back = requires(T & t) { t.push_back(*t.begin()); };
+#else
         template<typename T>
-        using has_push_back =
-            decltype(std::declval<T &>().push_back(*std::declval<T>().begin()));
+        using has_push_back = decltype(
+            std::declval<T &>().push_back(*std::declval<T &>().begin()));
+#endif
 
 #if BOOST_PARSER_USE_CONCEPTS
 
@@ -1457,7 +1462,11 @@ namespace boost { namespace parser {
         template<typename Container, typename T>
         void insert(Container & c, T && x)
         {
+#if BOOST_PARSER_USE_CONCEPTS
+            if constexpr (has_push_back<Container>) {
+#else
             if constexpr (is_detected_v<has_push_back, Container>) {
+#endif
                 c.push_back((T &&) x);
             } else {
                 c.insert((T &&) x);

test/compile_attribute.cpp

@@ -8,6 +8,48 @@
 
 using namespace boost::parser;
 
+#if defined(__cpp_explicit_this_parameter)
+#    define BOOST_PARSER_TEST_EXPLICIT_THIS 1
+#elif defined(__clang__)
+#    if __has_extension(cxx_explicit_this_parameter)
+#        define BOOST_PARSER_TEST_EXPLICIT_THIS 1
+#    endif
+#endif
+
+#if defined(BOOST_PARSER_TEST_EXPLICIT_THIS)
+struct explicit_object_parameter_container
+{
+    using iterator = int *;
+
+    iterator begin(this explicit_object_parameter_container & self)
+    {
+        return self.values_;
+    }
+    iterator end(this explicit_object_parameter_container & self)
+    {
+        return self.values_ + self.size_;
+    }
+    iterator insert(iterator pos, int value)
+    {
+        *pos = value;
+        return pos;
+    }
+    void push_back(this explicit_object_parameter_container & self, int value)
+    {
+        self.values_[self.size_++] = value;
+    }
+
+    int values_[4] = {};
+    int size_ = 0;
+};
+
+void compile_explicit_object_parameter_container()
+{
+    explicit_object_parameter_container result;
+    parse("1 2", +int_, ws, result);
+}
+#endif
+
 void compile_attribute_non_unicode()
 {
     // range
@@ -985,6 +1027,9 @@ void compile_attribute_sentinel()
 
 void compile_attribute()
 {
+#if defined(BOOST_PARSER_TEST_EXPLICIT_THIS)
+    compile_explicit_object_parameter_container();
+#endif
     compile_attribute_non_unicode();
     compile_attribute_unicode_utf8();
     compile_attribute_unicode_utf32();