util: Implement Expected::operator*()&&

It is currently unused, but implementing it is closer to std::expected.

src/test/util_expected_tests.cpp

@@ -50,6 +50,13 @@ BOOST_AUTO_TEST_CASE(expected_value_rvalue)
     BOOST_CHECK_EQUAL(*moved, 5);
 }
 
+BOOST_AUTO_TEST_CASE(expected_deref_rvalue)
+{
+    Expected<std::unique_ptr<int>, int> no_copy{std::make_unique<int>(5)};
+    const auto moved{*std::move(no_copy)};
+    BOOST_CHECK_EQUAL(*moved, 5);
+}
+
 BOOST_AUTO_TEST_CASE(expected_value_or)
 {
     Expected<std::unique_ptr<int>, int> no_copy{std::make_unique<int>(1)};

src/util/expected.h

@@ -88,8 +88,9 @@ public:
     constexpr E& error() & noexcept LIFETIMEBOUND { return *Assert(std::get_if<1>(&m_data)); }
     constexpr E&& error() && noexcept LIFETIMEBOUND { return std::move(error()); }
 
-    constexpr T& operator*() noexcept LIFETIMEBOUND { return value(); }
-    constexpr const T& operator*() const noexcept LIFETIMEBOUND { return value(); }
+    constexpr T& operator*() & noexcept LIFETIMEBOUND { return value(); }
+    constexpr const T& operator*() const& noexcept LIFETIMEBOUND { return value(); }
+    constexpr T&& operator*() && noexcept LIFETIMEBOUND { return std::move(value()); }
 
     constexpr T* operator->() noexcept LIFETIMEBOUND { return &value(); }
     constexpr const T* operator->() const noexcept LIFETIMEBOUND { return &value(); }