More void support

tests/bases.cpp

@@ -15,6 +15,13 @@ TEST_CASE("Triviality", "[bases.triviality]") {
     REQUIRE(std::is_trivially_move_assignable<tl::expected<int,int>>::value);
     REQUIRE(std::is_trivially_destructible<tl::expected<int,int>>::value);
 
+    REQUIRE(std::is_trivially_copy_constructible<tl::expected<void,int>>::value);
+    REQUIRE(std::is_trivially_copy_assignable<tl::expected<void,int>>::value);
+    REQUIRE(std::is_trivially_move_constructible<tl::expected<void,int>>::value);
+    REQUIRE(std::is_trivially_move_assignable<tl::expected<void,int>>::value);
+    REQUIRE(std::is_trivially_destructible<tl::expected<void,int>>::value);
+
+
     {
         struct T {
             T(const T&) = default;

tests/constructors.cpp

@@ -120,4 +120,15 @@ TEST_CASE("Constructors", "[constructors]") {
 		REQUIRE(!std::is_trivially_move_assignable<decltype(e)>::value);
 #	endif
 	}
+
+    {
+        tl::expected<void,int> e;
+        REQUIRE(e);
+    }
+
+    {
+        tl::expected<void,int> e (tl::unexpect, 42);
+        REQUIRE(!e);
+        REQUIRE(e.error() == 42);
+    }
 }

tl/expected.hpp

@@ -19,7 +19,6 @@
 
 #include <exception>
 #include <functional>
-#include <iostream>
 #include <type_traits>
 #include <utility>
 
@@ -528,10 +527,16 @@ template <class T, class E>
 struct expected_operations_base : expected_storage_base<T, E> {
   using expected_storage_base<T, E>::expected_storage_base;
 
-  template <class... Args> void construct(Args &&... args) noexcept {
+    template <class... Args> void construct(Args &&... args) noexcept {
-    new (std::addressof(this->m_val)) T(std::forward<Args>(args)...);
+        new (std::addressof(this->m_val)) T(std::forward<Args>(args)...);
-    this->m_has_val = true;
+        this->m_has_val = true;
-  }
+    }
+
+    template <class Rhs>
+    void construct_with(Rhs && rhs) noexcept {
+        new (std::addressof(this->m_val)) T(std::forward<Rhs>(rhs).get());
+        this->m_has_val = true;
+    }
 
   template <class... Args> void construct_error(Args &&... args) noexcept {
     new (std::addressof(this->m_unexpect))
@@ -678,6 +683,12 @@ struct expected_operations_base<void,E> : expected_storage_base<void, E> {
     this->m_has_val = true;
   }
 
+  template <class Rhs>
+  void construct_with(Rhs && rhs) noexcept {
+      this->m_has_val = true;
+  }
+
+
   template <class... Args> void construct_error(Args &&... args) noexcept {
     new (std::addressof(this->m_unexpect))
         unexpected<E>(std::forward<Args>(args)...);
@@ -735,7 +746,7 @@ struct expected_copy_base<T, E, false> : expected_operations_base<T, E> {
   expected_copy_base(const expected_copy_base &rhs)
       : expected_operations_base<T, E>(no_init) {
     if (rhs.has_value()) {
-      this->construct(rhs.get());
+      this->construct_with(rhs);
     } else {
       this->construct_error(rhs.geterr());
     }
@@ -772,7 +783,7 @@ struct expected_move_base<T, E, false> : expected_copy_base<T, E> {
       std::is_nothrow_move_constructible<T>::value)
       : expected_copy_base<T, E>(no_init) {
     if (rhs.has_value()) {
-      this->construct(std::move(rhs.get()));
+      this->construct_with(std::move(rhs));
     } else {
       this->construct_error(std::move(rhs.geterr()));
     }
@@ -1072,46 +1083,26 @@ public:
   /// is returned.
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &;
   template <class F> TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) & {
-    using result = detail::invoke_result_t<F, T &>;
+      return and_then_impl(*this, std::forward<F>(f));
-    static_assert(detail::is_expected<result>::value,
-                  "F must return an expected");
-
-    return has_value() ? detail::invoke(std::forward<F>(f), **this)
-                       : result(unexpect, this->error());
   }
 
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &&;
   template <class F> TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) && {
-    using result = detail::invoke_result_t<F, T &&>;
+      return and_then_impl(std::move(*this), std::forward<F>(f));
-    static_assert(detail::is_expected<result>::value,
-                  "F must return an expected");
-
-    return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
-                       : result(unexpect, std::move(this->error()));
   }
 
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &;
   template <class F> constexpr auto and_then(F &&f) const & {
-    using result = detail::invoke_result_t<F, const T &>;
+      return and_then_impl(*this, std::forward<F>(f));
-    static_assert(detail::is_expected<result>::value,
-                  "F must return an expected");
-
-    return has_value() ? detail::invoke(std::forward<F>(f), **this)
-                       : result(unexpect, this->error());
   }
 
 #ifndef TL_EXPECTED_NO_CONSTRR
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &&;
   template <class F> constexpr auto and_then(F &&f) const && {
-    using result = detail::invoke_result_t<F, const T &&>;
+      return and_then_impl(std::move(*this), std::forward<F>(f));
-    static_assert(detail::is_expected<result>::value,
-                  "F must return an expected");
-
-    return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
-                       : result(unexpect, std::move(this->error()));
   }
 #endif
 
@@ -1126,50 +1117,30 @@ public:
   /// is returned.
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &;
   template <class F>
-  TL_EXPECTED_11_CONSTEXPR detail::invoke_result_t<F, T &> and_then(F &&f) & {
+  TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) & -> decltype(and_then_impl(*this, std::forward<F>(f))) {
-    using result = detail::invoke_result_t<F, T &>;
+      return and_then_impl(*this, std::forward<F>(f));
-    static_assert(detail::is_expected<result>::value,
-                  "F must return an expected");
-
-    return has_value() ? detail::invoke(std::forward<F>(f), **this)
-                       : result(unexpect, this->error());
   }
 
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &&;
   template <class F>
-  TL_EXPECTED_11_CONSTEXPR detail::invoke_result_t<F, T &&> and_then(F &&f) && {
+  TL_EXPECTED_11_CONSTEXPR auto and_then(F &&f) && -> decltype(and_then_impl(std::move(*this), std::forward<F>(f))) {
-    using result = detail::invoke_result_t<F, T &&>;
+      return and_then_impl(std::move(*this), std::forward<F>(f));
-    static_assert(detail::is_expected<result>::value,
-                  "F must return an expected");
-
-    return has_value() ? detail::invoke(std::forward<F>(f), **this)
-                       : result(unexpect, std::move(this->error()));
   }
 
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &;
   template <class F>
-  constexpr detail::invoke_result_t<F, const T &> and_then(F &&f) const & {
+  constexpr auto and_then(F &&f) const & -> decltype(and_then_impl(*this, std::forward<F>(f))) {
-    using result = detail::invoke_result_t<F, const T &>;
+      return and_then_impl(*this, std::forward<F>(f));
-    static_assert(detail::is_expected<result>::value,
-                  "F must return an expected");
-
-    return has_value() ? detail::invoke(std::forward<F>(f), **this)
-                       : result(unexpect, this->error());
   }
 
 #ifndef TL_EXPECTED_NO_CONSTRR
   /// \group and_then
   /// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &&;
   template <class F>
-  constexpr detail::invoke_result_t<F, const T &&> and_then(F &&f) const && {
+  constexpr auto and_then(F &&f) const &&  -> decltype(and_then_impl(std::move(*this), std::forward<F>(f))) {
-    using result = detail::invoke_result_t<F, const T &&>;
+      return and_then_impl(std::move(*this), std::forward<F>(f));
-    static_assert(detail::is_expected<result>::value,
-                  "F must return an expected");
-
-    return has_value() ? detail::invoke(std::forward<F>(f), **this)
-                       : result(unexpect, std::move(this->error()));
   }
 #endif
 #endif
@@ -1514,15 +1485,16 @@ public:
 
   template <
       class U = T,
+      class G = T,
       detail::enable_if_t<std::is_nothrow_constructible<T, U &&>::value> * =
       nullptr,
-      detail::enable_if_t<!std::is_void<U>::value>* = nullptr,
+      detail::enable_if_t<!std::is_void<G>::value>* = nullptr,
       detail::enable_if_t<
           (!std::is_same<expected<T, E>, detail::decay_t<U>>::value &&
            !detail::conjunction<std::is_scalar<T>,
                                 std::is_same<T, detail::decay_t<U>>>::value &&
            std::is_constructible<T, U>::value &&
-//           std::is_assignable<T &, U>::value &&
+           std::is_assignable<G &, U>::value &&
            std::is_nothrow_move_constructible<E>::value)> * = nullptr
       >
   expected &operator=(U &&v) {
@@ -1540,6 +1512,7 @@ public:
   /// \exclude
   template <
       class U = T,
+      class G = T,
       detail::enable_if_t<!std::is_nothrow_constructible<T, U &&>::value> * =
       nullptr,
       detail::enable_if_t<!std::is_void<U>::value>* = nullptr,
@@ -1548,7 +1521,7 @@ public:
            !detail::conjunction<std::is_scalar<T>,
                                 std::is_same<T, detail::decay_t<U>>>::value &&
            std::is_constructible<T, U>::value &&
-//           std::is_assignable<T &, U>::value &&
+           std::is_assignable<G &, U>::value &&
            std::is_nothrow_move_constructible<E>::value)> * = nullptr
       >
   expected &operator=(U &&v) {
@@ -1782,10 +1755,61 @@ public:
 
 /// \exclude
 namespace detail {
-template <class Exp> using exp_t = typename detail::decay_t<Exp>::error_type;
+template <class Exp> using exp_t = typename detail::decay_t<Exp>::value_type;
 template <class Exp> using err_t = typename detail::decay_t<Exp>::error_type;
 template <class Exp, class Ret> using ret_t = expected<Ret, err_t<Exp>>;
 
+#ifdef TL_EXPECTED_CXX14
+template <class Exp, class F,
+          class Ret = decltype(detail::invoke(std::declval<F>(),
+                                              *std::declval<Exp>())),
+    detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr>
+constexpr auto and_then_impl(Exp &&exp, F &&f) {
+    static_assert(detail::is_expected<Ret>::value,
+                  "F must return an expected");
+
+    return exp.has_value() ? detail::invoke(std::forward<F>(f), *std::forward<Exp>(exp))
+                       : Ret(unexpect, exp.error());
+}
+
+template <class Exp, class F,
+          class Ret = decltype(detail::invoke(std::declval<F>(),
+                                              *std::declval<Exp>())),
+    detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr>
+constexpr auto and_then_impl(Exp &&exp, F &&f) {
+    static_assert(detail::is_expected<Ret>::value,
+                  "F must return an expected");
+
+    return exp.has_value() ? detail::invoke(std::forward<F>(f))
+                       : Ret(unexpect, exp.error());
+}
+#else
+    template<class>struct TC;
+template <class Exp, class F,
+          class Ret = decltype(detail::invoke(std::declval<F>(),
+                                              *std::declval<Exp>())),
+    detail::enable_if_t<!std::is_void<exp_t<Exp>>::value> * = nullptr>
+ auto and_then_impl(Exp &&exp, F &&f) -> Ret {
+    static_assert(detail::is_expected<Ret>::value,
+                  "F must return an expected");
+
+    return exp.has_value() ? detail::invoke(std::forward<F>(f), *std::forward<Exp>(exp))
+                           : Ret(unexpect, exp.error());
+}
+
+template <class Exp, class F,
+          class Ret = decltype(detail::invoke(std::declval<F>(),
+                                              *std::declval<Exp>())),
+    detail::enable_if_t<std::is_void<exp_t<Exp>>::value> * = nullptr>
+constexpr auto and_then_impl(Exp &&exp, F &&f) -> Ret {
+    static_assert(detail::is_expected<Ret>::value,
+                  "F must return an expected");
+
+    return exp.has_value() ? detail::invoke(std::forward<F>(f))
+                       : Ret(unexpect, exp.error());
+}
+#endif
+
 #ifdef TL_EXPECTED_CXX14
 template <class Exp, class F,
           class Ret = decltype(detail::invoke(std::declval<F>(),