From 52bbec06cfc8f89ee8aed49599f879c9a653b504 Mon Sep 17 00:00:00 2001
From: Emil Dotchevski <emildotchevski@gmail.com>
Date: Tue, 16 Jan 2024 22:32:42 -0800
Subject: [PATCH] Minor changes in result member functions sfinae use

---
 include/boost/leaf/result.hpp | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/include/boost/leaf/result.hpp b/include/boost/leaf/result.hpp
index b7817723..9e72880a 100644
--- a/include/boost/leaf/result.hpp
+++ b/include/boost/leaf/result.hpp
@@ -329,10 +329,19 @@ class BOOST_LEAF_SYMBOL_VISIBLE result
         }
     }
 
+    template <class U>
+    void move_assign( result<U> && x ) noexcept
+    {
+        destroy();
+        what_ = move_from(std::move(x));
+    }
+
 public:
 
     using value_type = T;
 
+    // NOTE: Copy constructor implicitly deleted.
+
     result( result && x ) noexcept:
         what_(move_from(std::move(x)))
     {
@@ -404,8 +413,8 @@ class BOOST_LEAF_SYMBOL_VISIBLE result
     {
     }
 
-    template <class Enum>
-    result( Enum e, typename std::enable_if<std::is_error_code_enum<Enum>::value, int>::type * = nullptr ) noexcept:
+    template <class Enum, class = typename std::enable_if<std::is_error_code_enum<Enum>::value, int>::type>
+    result( Enum e ) noexcept:
         what_(error_id(e))
     {
     }
@@ -416,18 +425,18 @@ class BOOST_LEAF_SYMBOL_VISIBLE result
         destroy();
     }
 
+    // NOTE: Assignment operator implicitly deleted.
+
     result & operator=( result && x ) noexcept
     {
-        destroy();
-        what_ = move_from(std::move(x));
+        move_assign(std::move(x));
         return *this;
     }
 
-    template <class U>
+    template <class U, class = typename std::enable_if<std::is_convertible<U, T>::value>::type>
     result & operator=( result<U> && x ) noexcept
     {
-        destroy();
-        what_ = move_from(std::move(x));
+        move_assign(std::move(x));
         return *this;
     }
 
@@ -627,6 +636,7 @@ class BOOST_LEAF_SYMBOL_VISIBLE result<void>:
 
     using value_type = void;
 
+    // NOTE: Copy constructor implicitly deleted.
     result( result && x ) noexcept:
         base(std::move(x))
     {
@@ -647,8 +657,8 @@ class BOOST_LEAF_SYMBOL_VISIBLE result<void>:
     {
     }
 
-    template <class Enum>
-    result( Enum e, typename std::enable_if<std::is_error_code_enum<Enum>::value, Enum>::type * = nullptr ) noexcept:
+    template <class Enum, class = typename std::enable_if<std::is_error_code_enum<Enum>::value, int>::type>
+    result( Enum e ) noexcept:
         base(e)
     {
     }
@@ -658,6 +668,13 @@ class BOOST_LEAF_SYMBOL_VISIBLE result<void>:
     {
     }
 
+    // NOTE: Assignment operator implicitly deleted.
+    result & operator=( result && x ) noexcept
+    {
+        base::move_assign(std::move(x));
+        return *this;
+    }
+
     void value() const
     {
         base::enforce_value_state();