Allow throwing exceptions from pfr::structure_to_tuple (fixes #155) … (#160)

…and fix some warnings

test/core/run/structure_to_tuple.cpp

@@ -0,0 +1,91 @@
+// Copyright (c) 2020-2024 Antony Polukhin
+//
+// 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 <boost/core/lightweight_test.hpp>
+
+#include <boost/pfr/core.hpp>
+
+namespace some {
+    struct struct1{ int i; };
+    struct struct2{ int i; short s;  };
+}
+
+
+void test_single_field() {
+    {
+        some::struct1 s{1};
+        auto s_tuple = boost::pfr::structure_to_tuple(s);
+        BOOST_TEST_EQ(std::get<0>(s_tuple), 1);
+
+        static_assert(std::is_same<
+            std::tuple<int>, decltype(s_tuple)
+        >::value, "");
+    }
+    {
+        const some::struct1 s{1};
+        auto s_tuple = boost::pfr::structure_to_tuple(s);
+        BOOST_TEST_EQ(std::get<0>(s_tuple), 1);
+
+        static_assert(std::is_same<
+            std::tuple<int>, decltype(s_tuple)
+        >::value, "");
+    }
+}
+
+
+void test_two_fields() {
+    {
+        some::struct2 s{1, 2};
+        auto s_tuple = boost::pfr::structure_to_tuple(s);
+        BOOST_TEST_EQ(std::get<0>(s_tuple), 1);
+        BOOST_TEST_EQ(std::get<1>(s_tuple), 2);
+
+        static_assert(std::is_same<
+            std::tuple<int, short>, decltype(s_tuple)
+        >::value, "");
+    }
+    {
+        const some::struct2 s{1, 2};
+        auto s_tuple = boost::pfr::structure_to_tuple(s);
+        BOOST_TEST_EQ(std::get<0>(s_tuple), 1);
+        BOOST_TEST_EQ(std::get<1>(s_tuple), 2);
+
+        static_assert(std::is_same<
+            std::tuple<int, short>, decltype(s_tuple)
+        >::value, "");
+    }
+}
+
+// Test from https://github.com/boostorg/pfr/issues/155
+void test_throwing_field() {
+#if BOOST_PFR_USE_CPP17 || BOOST_PFR_USE_LOOPHOLE
+    struct throw_on_copy {
+        throw_on_copy() = default;
+        throw_on_copy(const throw_on_copy&){ throw 42; }
+    };
+
+    struct throwing_struct {
+        int i;
+        throw_on_copy s;
+    };
+
+    throwing_struct s {10, {}};
+    try {
+        std::tuple<int, throw_on_copy> t = boost::pfr::structure_to_tuple(s);
+        BOOST_TEST(false); // the above line should throw
+        (void)t;
+    } catch (...) {}
+#endif
+}
+
+int main() {
+    test_single_field();
+    test_two_fields();
+    test_throwing_field();
+
+    return boost::report_errors();
+}
+
+