From b074bee4096ef174c5f966fa4a6e046dad956c0d Mon Sep 17 00:00:00 2001
From: Deniz Evrenci <denizevrenci@gmail.com>
Date: Mon, 8 Jul 2019 19:32:17 +0900
Subject: [PATCH] Fix implementation of optional<T&>::emplace()

---
 include/tl/optional.hpp | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/include/tl/optional.hpp b/include/tl/optional.hpp
index 9cba0b8..ad8ae2f 100644
--- a/include/tl/optional.hpp
+++ b/include/tl/optional.hpp
@@ -1982,15 +1982,12 @@ public:
     return *this;
   }
 
-  /// Constructs the value in-place, destroying the current one if there is
-  /// one.
-  template <class... Args> T &emplace(Args &&... args) noexcept {
-    static_assert(std::is_constructible<T, Args &&...>::value,
-                  "T must be constructible with Args");
-
-    *this = nullopt;
-    this->construct(std::forward<Args>(args)...);
-    return value();
+  /// Rebinds this optional to `u`.
+  template <class U = T,
+            detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value>
+                * = nullptr>
+  optional &emplace(U &&u) noexcept {
+    return *this = std::forward<U>(u);
   }
 
   void swap(optional &rhs) noexcept { std::swap(m_value, rhs.m_value); }