Support result<X> & fv, where fv returns void. Refs #119.

test/result_and_fn1v.cpp

@@ -55,6 +55,10 @@ int k()
     return 7;
 }
 
+void fv1( int /*x*/ )
+{
+}
+
 int main()
 {
     {
@@ -199,5 +203,45 @@ int main()
         BOOST_TEST( r2.has_error() );
     }
 
+    {
+        result<int> r( 1 );
+        result<void> r2 = r & fv1;
+
+        BOOST_TEST( r2.has_value() );
+    }
+
+    {
+        result<int> const r( 1 );
+        result<void> r2 = r & fv1;
+
+        BOOST_TEST( r2.has_value() );
+    }
+
+    {
+        result<void> r2 = result<int>( 1 ) & fv1;
+
+        BOOST_TEST( r2.has_value() );
+    }
+
+    {
+        result<int, E> r( in_place_error );
+        result<void, E> r2 = r & fv1;
+
+        BOOST_TEST( r2.has_error() );
+    }
+
+    {
+        result<int, E> const r( in_place_error );
+        result<void, E> r2 = r & fv1;
+
+        BOOST_TEST( r2.has_error() );
+    }
+
+    {
+        result<void, E> r2 = result<int, E>( in_place_error ) & fv1;
+
+        BOOST_TEST( r2.has_error() );
+    }
+
     return boost::report_errors();
 }