BOOST_<level>_NO_THROW with return value

[redboltz]

I'm using BOOST_REQUIRE_NO_THROW() as follows:

#define BOOST_TEST_MAIN
#include <boost/test/included/unit_test.hpp>

struct nc {
    nc(int v): v { v } {}
    nc() = delete;
    nc(nc const&) = delete;
    nc(nc&&) = default;
    int v;
};

nc success() {
    return nc(1);
}

nc fail() {
    throw(42);
    return nc(2);
}

BOOST_AUTO_TEST_CASE(test_case1) {
    BOOST_REQUIRE_NO_THROW(
        auto v1 = success();
        std::cout << v1.v << std::endl;
        auto v2 = fail();
        std::cout << v2.v << std::endl;
    );
}

It works well. But output is not easy to understand.

Here is runnable demo: https://wandbox.org/permlink/KnsKJ9xq9htug3iG

The output is:

Running 1 test case...
1
prog.cc(27): fatal error: in "test_case1": unexpected exception thrown by auto v1 = success(); std::cout << v1.v << std::endl; auto v2 = fail(); std::cout << v2.v << std::endl;

*** 1 failure is detected in the test module "Master Test Suite"

All lines in BOOST_REQUIRE_NO_THROW() seems to regard as one line.

Unfortunately the following notation is not accepted.

    BOOST_REQUIRE_NO_THROW(nc v1 = success());
    std::cout << v1.v << std::endl; // no v1 in the scope

    nc v1 = BOOST_REQUIRE_NO_THROW(success()); // Syntax error
    std::cout << v1.v << std::endl;

Finally I found a workaround using optional.

#define BOOST_TEST_MAIN
#include <boost/test/included/unit_test.hpp>
#include <optional>

struct nc {
    nc(int v): v { v } {}
    nc() = delete;
    nc(nc const&) = delete;
    nc(nc&&) = default;
    int v;
};

nc success() {
    return nc(1);
}

nc fail() {
    throw(42);
    return nc(2);
}

BOOST_AUTO_TEST_CASE(test_case1) {
    std::optional<nc> v1;
    BOOST_REQUIRE_NO_THROW(v1.emplace(success()));
    std::cout << v1->v << std::endl;
    
    std::optional<nc> v2;
    BOOST_REQUIRE_NO_THROW(v2.emplace(fail()));
    std::cout << v2->v << std::endl;
}

It works well and the error is reported accurate line.

Here is runnable demo: https://wandbox.org/permlink/gEYLIxgofWub2G0j

The output is:

Running 1 test case...
1
prog.cc(28): fatal error: in "test_case1": unexpected exception thrown by v2.emplace(fail())

*** 1 failure is detected in the test module "Master Test Suite"

I think that the optional workaround is acceptable. But if there is better way, I'd like to know.