From 7b4495d3c4040d8f56c05dd254d76269d4471623 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Fri, 8 Apr 2022 18:26:23 +0100
Subject: [PATCH] libstdc++: Fix constraints on std::expected<void, E>
 constructor [PR105153]

libstdc++-v3/ChangeLog:

	PR libstdc++/105153
	* include/std/expected
	(expected<void,E>::expected(expected<U,G>&&)): Fix constraints.
	* testsuite/20_util/expected/cons.cc: Check constructor.
---
 libstdc++-v3/include/std/expected               |  4 ++--
 libstdc++-v3/testsuite/20_util/expected/cons.cc | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/std/expected b/libstdc++-v3/include/std/expected
index 1864e866..3446d6d 100644
--- a/libstdc++-v3/include/std/expected
+++ b/libstdc++-v3/include/std/expected
@@ -966,8 +966,8 @@ namespace __expected
 	}
 
       template<typename _Up, typename _Gr>
-	requires is_void_v<_Tp>
-	      && is_constructible_v<_Er, const _Gr&>
+	requires is_void_v<_Up>
+	      && is_constructible_v<_Er, _Gr>
 	      && (!__cons_from_expected<_Up, _Gr>)
 	constexpr explicit(!is_convertible_v<_Gr, _Er>)
 	expected(expected<_Up, _Gr>&& __x)
diff --git a/libstdc++-v3/testsuite/20_util/expected/cons.cc b/libstdc++-v3/testsuite/20_util/expected/cons.cc
index 1fe5b7b..6946858 100644
--- a/libstdc++-v3/testsuite/20_util/expected/cons.cc
+++ b/libstdc++-v3/testsuite/20_util/expected/cons.cc
@@ -162,6 +162,22 @@ test_copy()
   return true;
 }
 
+constexpr bool
+test_pr105153()
+{
+  struct E {
+    E(int&&) = delete;
+    E(const int&);
+  };
+
+  std::expected<void, E> e(std::expected<void, int>{});
+
+  static_assert( ! std::is_constructible_v<std::expected<void, int>,
+					   std::expected<int, int>> );
+
+  return true;
+}
+
 int main()
 {
   test_default();
@@ -172,4 +188,6 @@ int main()
   static_assert( test_err() );
   test_copy();
   static_assert( test_copy() );
+  test_pr105153();
+  static_assert( test_pr105153() );
 }
-- 
2.7.4