Fix windows build

Author: PingLiuPing

src/iceberg/expected.h

@@ -824,19 +824,7 @@ struct copy_assign_base<T, E, true, false> : move_ctor_base<T, E> {
       noexcept(std::is_nothrow_copy_constructible_v<T> &&
                std::is_nothrow_copy_assignable_v<T> &&
                std::is_nothrow_copy_constructible_v<E> &&
-               std::is_nothrow_copy_assignable_v<E>) {
-    if (this->m_has_val && rhs.m_has_val) {
-      this->m_val = rhs.m_val;
-    } else if (this->m_has_val) {
-      expected_detail::reinit_expected(this->m_unexpect, this->m_val, rhs.m_unexpect);
-    } else if (rhs.m_has_val) {
-      expected_detail::reinit_expected(this->m_val, this->m_unexpect, rhs.m_val);
-    } else {
-      this->m_unexpect = rhs.m_unexpect;
-    }
-    this->m_has_val = rhs.m_has_val;
-    return *this;
-  }
+               std::is_nothrow_copy_assignable_v<E>);
 
   copy_assign_base& operator=(copy_assign_base&& rhs) = default;
 };
@@ -851,24 +839,49 @@ struct copy_assign_base<void, E, true, false> : move_ctor_base<void, E> {
   copy_assign_base(copy_assign_base&& rhs) = default;
 
   constexpr copy_assign_base& operator=(const copy_assign_base& rhs) noexcept(
-      std::is_nothrow_copy_constructible_v<E> && std::is_nothrow_copy_assignable_v<E>) {
-    if (this->m_has_val && rhs.m_has_val) {
-      // no-op
-    } else if (this->m_has_val) {
-      std::construct_at(std::addressof(this->m_unexpect), rhs.m_unexpect);
-      this->m_has_val = false;
-    } else if (rhs.m_has_val) {
-      this->m_unexpect.~E();
-      this->m_has_val = true;
-    } else {
-      this->m_unexpect = rhs.m_unexpect;
-    }
-    return *this;
-  }
+      std::is_nothrow_copy_constructible_v<E> && std::is_nothrow_copy_assignable_v<E>);
 
   copy_assign_base& operator=(copy_assign_base&& rhs) = default;
 };
 
+template <class T, class E>
+constexpr copy_assign_base<T, E, true, false>& copy_assign_base<T, E, true, false>::
+operator=(const copy_assign_base<T, E, true, false>& rhs) noexcept(
+    std::is_nothrow_copy_constructible_v<T> && std::is_nothrow_copy_assignable_v<T> &&
+    std::is_nothrow_copy_constructible_v<E> && std::is_nothrow_copy_assignable_v<E>) {
+  if (this->m_has_val && rhs.m_has_val) {
+    this->m_val = rhs.m_val;
+  } else if (this->m_has_val) {
+    expected_detail::reinit_expected(this->m_unexpect, this->m_val, rhs.m_unexpect);
+  } else if (rhs.m_has_val) {
+    expected_detail::reinit_expected(this->m_val, this->m_unexpect, rhs.m_val);
+  } else {
+    this->m_unexpect = rhs.m_unexpect;
+  }
+  this->m_has_val = rhs.m_has_val;
+  return *this;
+}
+
+template <class E>
+constexpr copy_assign_base<void, E, true, false>&
+copy_assign_base<void, E, true, false>::operator=(
+    const copy_assign_base<void, E, true, false>&
+        rhs) noexcept(std::is_nothrow_copy_constructible_v<E> &&
+                      std::is_nothrow_copy_assignable_v<E>) {
+  if (this->m_has_val && rhs.m_has_val) {
+    // no-op
+  } else if (this->m_has_val) {
+    std::construct_at(std::addressof(this->m_unexpect), rhs.m_unexpect);
+    this->m_has_val = false;
+  } else if (rhs.m_has_val) {
+    this->m_unexpect.~E();
+    this->m_has_val = true;
+  } else {
+    this->m_unexpect = rhs.m_unexpect;
+  }
+  return *this;
+}
+
 template <class T, class E>
 inline constexpr bool is_expected_move_assignable_v =
     is_move_assignable_or_void_v<T> && is_move_constructible_or_void_v<T> &&

src/iceberg/test/expected_test.cc

@@ -20,7 +20,9 @@
 #include "iceberg/expected.h"
 
 #include <functional>
+#include <memory>
 #include <type_traits>
+#include <vector>
 
 #include <gtest/gtest.h>
 
@@ -77,6 +79,13 @@ TEST(ExpectedTest, ConversionToValueWithoutDefaultConstructor) {
                 iceberg::expected<std::reference_wrapper<int>, int>>));
 }
 
+TEST(ExpectedTest, SupportsMoveOnlyContainerValue) {
+  using MoveOnlyContainer = std::vector<std::unique_ptr<int>>;
+  iceberg::expected<MoveOnlyContainer, int> value{std::in_place};
+
+  EXPECT_TRUE(value.has_value());
+}
+
 namespace {
 
 // Counts live objects, to catch a value constructed without being destroyed.