Support construction/assignment from reference_wrapper

Fixes TartanLlama#67.
Quuxplusone · Sep 8, 2024 · 1270624 · 1270624
1 parent 3a1209d
commit 1270624
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Showing 2 changed files with 20 additions and 8 deletions.
diff --git a/include/tl/optional.hpp b/include/tl/optional.hpp
@@ -1936,11 +1936,10 @@ template <class T> class optional<T &> {
   TL_OPTIONAL_11_CONSTEXPR optional(optional &&rhs) = default;
 
   /// Constructs the stored value with `u`.
-  template <class U = T,
-            detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value>
+  template <class U,
+            detail::enable_if_t<std::is_convertible<U, T&>::value>
                 * = nullptr>
-  constexpr optional(U &&u)  noexcept : m_value(std::addressof(u)) {
-    static_assert(std::is_lvalue_reference<U>::value, "U must be an lvalue");
+  constexpr optional(U &&u)  noexcept : m_value(std::addressof(static_cast<T&>(u))) {
   }
 
   template <class U>
@@ -1964,12 +1963,11 @@ template <class T> class optional<T &> {
   optional &operator=(const optional &rhs) = default;
 
   /// Rebinds this optional to `u`.
-  template <class U = T,
-            detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value>
+  template <class U,
+            detail::enable_if_t<std::is_convertible<U, T&>::value>
                 * = nullptr>
   optional &operator=(U &&u) {
-    static_assert(std::is_lvalue_reference<U>::value, "U must be an lvalue");
-    m_value = std::addressof(u);
+    m_value = std::addressof(static_cast<T&>(u));
     return *this;
   }
 

diff --git a/tests/issues.cpp b/tests/issues.cpp
@@ -43,3 +43,17 @@ TEST_CASE("issue 33") {
     REQUIRE(*a == 42);
     REQUIRE(a.has_value());
 }
+
+TEST_CASE("issue 66") {
+    int i = 42;
+    int j = 43;
+    tl::optional<std::reference_wrapper<int>> a = std::ref(i);
+    REQUIRE(&a.value().get() == &i);
+    a = std::ref(j);
+    REQUIRE(&a.value().get() == &j);
+
+    tl::optional<int&> b = std::ref(i);
+    REQUIRE(&b.value() == &i);
+    b = std::ref(j);
+    REQUIRE(&b.value() == &j);
+}