From 22906db64970de2d2af46ddc1b5990c701b93368 Mon Sep 17 00:00:00 2001
From: Martin Moene <martin.moene@gmail.com>
Date: Wed, 2 Nov 2022 20:48:32 +0100
Subject: [PATCH] Fix disabling of swap() (#50, thanks @negatratoron)

---
 include/nonstd/expected.hpp |  5 +++--
 test/expected.t.cpp         | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/include/nonstd/expected.hpp b/include/nonstd/expected.hpp
index f2b7f94..d9473a7 100644
--- a/include/nonstd/expected.hpp
+++ b/include/nonstd/expected.hpp
@@ -1002,11 +1002,12 @@ class unexpected_type
 
     // x.x.5.2.4 Swap
 
+    template< typename U=E >
     nsel_REQUIRES_R( void,
-        std17::is_swappable<E>::value
+        std17::is_swappable<U>::value
     )
     swap( unexpected_type & other ) noexcept (
-        std17::is_nothrow_swappable<E>::value
+        std17::is_nothrow_swappable<U>::value
     )
     {
         using std::swap;
diff --git a/test/expected.t.cpp b/test/expected.t.cpp
index f7664ab..2f70046 100644
--- a/test/expected.t.cpp
+++ b/test/expected.t.cpp
@@ -1820,6 +1820,24 @@ CASE( "pr-41" )
     EXPECT( std::move(cc).error() == 7 );
 }
 
+// issue #50, https://github.com/martinmoene/expected-lite/issues/50
+
+namespace issue_50 {
+
+struct MyConstMemberNonMoveableObject
+{
+    const int x;
+    MyConstMemberNonMoveableObject( int x_ ) : x( x_ ) {}
+    MyConstMemberNonMoveableObject( MyConstMemberNonMoveableObject const & ) = default;
+};
+
+nonstd::unexpected_type<MyConstMemberNonMoveableObject> create_nonmoveable()
+{
+    return nonstd::make_unexpected<MyConstMemberNonMoveableObject>( MyConstMemberNonMoveableObject(3) );
+}
+
+} // namespace issue_50
+
 // -----------------------------------------------------------------------
 //  using as optional