X3: Cover position_tagged's features with test

test/x3/Jamfile

@@ -123,6 +123,7 @@ run attribute_type_check.cpp ;
 run fusion_map.cpp ;
 run x3_variant.cpp ;
 run error_handler.cpp ;
+run error_handler_positions.cpp ;
 run iterator_check.cpp ;
 
 run to_utf8.cpp ;

test/x3/error_handler_positions.cpp

@@ -0,0 +1,71 @@
+/*=============================================================================
+    Copyright (c) 2022 Denis Mikhailov
+    Distributed under the Boost Software License, Version 1.0. (See accompanying
+    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+=============================================================================*/
+#include <string>
+#include <vector>
+
+#include <boost/spirit/home/x3.hpp>
+#include <boost/spirit/home/x3/support/utility/annotate_on_success.hpp>
+
+#include <boost/core/lightweight_test.hpp>
+#include <string>
+#include <iostream>
+
+struct employee
+{
+  int age;
+  double salary;
+};
+
+struct employee_with_position_tagged : boost::spirit::x3::position_tagged
+{
+  int age;
+  double salary;
+};
+
+using iterator_type = std::string::const_iterator;
+using error_handler_type = boost::spirit::x3::error_handler<iterator_type>;
+
+std::string input = "Hello world!!";
+
+void test() {
+  {
+    error_handler_type error_handler{input.begin(), input.end(), std::cerr};
+    employee ast;
+    error_handler.tag(ast, input.begin() + 6, input.begin() + 11);
+    // const auto r = error_handler.position_of(ast);
+    // BOOST_TEST(r.empty());
+    BOOST_TEST(error_handler.get_position_cache().get_positions().empty());
+  }
+}
+
+void test_with_position_tagged() {
+  {
+    error_handler_type error_handler{input.begin(), input.end(), std::cerr};
+    employee_with_position_tagged ast;
+    error_handler.tag(ast, input.begin() + 6, input.begin() + 11);
+    const auto r = error_handler.position_of(ast);
+    const auto str = std::string{r.begin(), r.end()};
+    BOOST_TEST(!r.empty());
+    BOOST_TEST(str == "world");
+  }
+  {
+    std::stringstream stream;
+    error_handler_type error_handler{input.begin(), input.end(), stream};
+    employee_with_position_tagged ast;
+    error_handler.tag(ast, input.begin() + 6, input.begin() + 11);
+    error_handler(ast, "You were wrong");
+    BOOST_TEST_EQ(stream.str(), "In line 1:\nYou were wrong\nHello world!!\n      ~~~~~ <<-- Here\n");
+  }
+}
+
+int
+main()
+{
+  test();
+  test_with_position_tagged();
+  return boost::report_errors();
+}
+