Remove windows-2019 from ci.yml

add move_only_function

.github/workflows/ci.yml

@@ -39,18 +39,22 @@ jobs:
             install: g++-6
           - toolset: gcc-7
             cxxstd: "03,11,14,17"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: g++-7
           - toolset: gcc-8
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: g++-8
           - toolset: gcc-9
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
           - toolset: gcc-10
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: g++-10
           - toolset: gcc-11
             cxxstd: "03,11,14,17,2a"
@@ -90,37 +94,44 @@ jobs:
           - toolset: clang
             compiler: clang++-6.0
             cxxstd: "03,11,14,17"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: clang-6.0
           - toolset: clang
             compiler: clang++-7
             cxxstd: "03,11,14,17"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: clang-7
           - toolset: clang
             compiler: clang++-8
             cxxstd: "03,11,14,17"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: clang-8
           - toolset: clang
             compiler: clang++-9
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: clang-9
           - toolset: clang
             compiler: clang++-10
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: clang-10
           - toolset: clang
             compiler: clang++-11
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: clang-11
           - toolset: clang
             compiler: clang++-12
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            container: ubuntu:20.04
+            os: ubuntu-latest
             install: clang-12
           - toolset: clang
             compiler: clang++-13
@@ -246,14 +257,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - toolset: msvc-14.0
-            cxxstd: "14,latest"
-            addrmd: 32,64
-            os: windows-2019
-          - toolset: msvc-14.2
-            cxxstd: "14,17,20,latest"
-            addrmd: 32,64
-            os: windows-2019
           - toolset: msvc-14.3
             cxxstd: "14,17,20,latest"
             addrmd: 32,64
@@ -265,7 +268,7 @@ jobs:
           - toolset: gcc
             cxxstd: "03,11,14,17,2a"
             addrmd: 64
-            os: windows-2019
+            os: windows-2022
 
     runs-on: ${{matrix.os}}
 
@@ -305,7 +308,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-20.04
           - os: ubuntu-22.04
           - os: ubuntu-24.04
           - os: macos-13
@@ -355,7 +357,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-20.04
           - os: ubuntu-22.04
           - os: ubuntu-24.04
           - os: macos-13
@@ -415,7 +416,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-20.04
           - os: ubuntu-22.04
           - os: ubuntu-24.04
           - os: macos-13
@@ -473,8 +473,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: windows-2019
-          - os: windows-2022
+          - os: windows-latest
 
     runs-on: ${{matrix.os}}
 
@@ -522,8 +521,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: windows-2019
-          - os: windows-2022
+          - os: windows-latest
 
     runs-on: ${{matrix.os}}
 
@@ -589,8 +587,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: windows-2019
-          - os: windows-2022
+          - os: windows-latest
 
     runs-on: ${{matrix.os}}
 

doc/compat/changelog.adoc

@@ -8,6 +8,10 @@ https://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix: changelog_
 
+## Changes in 1.89.0
+
+* Added `move_only_function.hpp`.
+
 ## Changes in 1.87.0
 
 * Added `to_array.hpp` (contributed by Ruben Perez Hidalgo.)

doc/compat/move_only_function.adoc

@@ -0,0 +1,252 @@
+////
+Copyright 2025 Christian Mazakas
+Distributed under the Boost Software License, Version 1.0.
+https://www.boost.org/LICENSE_1_0.txt
+////
+
+[#move_only_function]
+# <boost/compat/move_only_function.hpp>
+:idprefix: ref_move_only_function_
+
+## Description
+
+The header `<boost/compat/move_only_function.hpp>` implements the {cpp}23 class https://en.cppreference.com/w/cpp/utility/functional/move_only_function.html[std::move_only_function].
+
+`move_only_function` is a polymorphic wrapper that stores and manages a https://en.cppreference.com/w/cpp/named_req/Callable[Callable], only requiring that the type supports move construction and move assignment.
+This is in contrast to the commonly used `std::function` which requires copyability of the underlying managed object.
+
+`move_only_function` supports every combination of `const`, `noexcept` and reference qualification (none, `&`, `&&`).
+
+## Example
+
+```cpp
+struct moveonly
+{
+    std::unique_ptr<int> p_ = std::make_unique<int>( 1234 );
+    auto operator()( int x ) noexcept { return *p_ + x; }
+};
+
+boost::compat::move_only_function<int( int ) noexcept> f( moveonly{} );
+std::cout << f( 4321 ) << std::endl;
+```
+
+## Synopsis
+
+```cpp
+namespace boost {
+namespace compat {
+
+template<class... S>
+class move_only_function;
+
+template< class T >
+struct in_place_type_t { explicit in_place_type_t() = default; };
+
+template<class R, class ...Args>
+class move_only_function<R( Args... ) /* cv */ /* ref */ noexcept( /* noex */)>
+{
+    move_only_function() noexcept;
+    move_only_function( std::nullptr_t ) noexcept;
+
+    template<class F>
+    move_only_function( F&& f );
+
+    template<class T, class ...CArgs>
+    explicit move_only_function( in_place_type_t<T>, CArgs&& ... args );
+
+    template<class T, class U, class ...CArgs>
+    explicit move_only_function( in_place_type_t<T>,
+                                 std::initializer_list<U> il, CArgs&& ... args );
+
+    move_only_function( move_only_function const& ) = delete;
+    move_only_function( move_only_function&& ) = default;
+
+    ~move_only_function() = default;
+
+    move_only_function& operator=( move_only_function&& rhs );
+    move_only_function& operator=( std::nullptr_t ) noexcept;
+    template<class F> move_only_function& operator=( F&& f );
+
+    friend bool operator==( move_only_function const& fn, std::nullptr_t ) noexcept;
+    friend bool operator!=( move_only_function const& fn, std::nullptr_t ) noexcept;
+
+    void swap( move_only_function& rhs ) noexcept;
+    friend void swap( move_only_function& lhs, move_only_function& rhs ) noexcept;
+
+    explicit operator bool() const noexcept;
+
+    R operator()( Args... args ) /* cv */ /* ref */ noexcept( /* noex */ );
+};
+
+} // namespace compat
+} // namespace boost
+
+```
+
+## Constructors
+
+### Default Constructor
+
+```cpp
+move_only_function() noexcept;
+```
+
+[horizontal]
+Effects::
+Constructs an empty `move_only_function` which manages no object.
+
+### Null Constructor
+
+```cpp
+move_only_function( std::nullptr_t ) noexcept;
+```
+
+[horizontal]
+Effects::
+Explicitly constructs an empty `move_only_function` using a nullptr value. Equivalent to default construction.
+
+### Object Constructor
+
+```cpp
+template<class F>
+move_only_function( F&& f );
+```
+
+[horizontal]
+Effects:;; Given `using VT = decay_t<F>`, directly constructs an instance of `VT` using `forward<F>(f)` and stores it as the target object. +
++
+If `F` is an empty function pointer, pointer-to-member or specialization of `move_only_function` then the constructed `move_only_function` is empty.
+Constraints:;;
++
+--
+* `remove_cv_ref<F>` is not the same type as `move_only_function`
+* `remove_cv_ref<F>` is not a specialization of `in_place_type_t`
+* `VT` must be callable with the provided cvref qualifiers and the provided argument types
+--
+
+### In-Place Constructor
+
+```cpp
+template<class T, class ...CArgs>
+explicit move_only_function( in_place_type_t<T>, CArgs&& ... args );
+```
+
+[horizontal]
+Effects:;; Constructs an object of type `T` using the provided args directly, storing it as the target object.
+Constraints:;;
++
+--
+* `is_constructible_v<T, CArgs...>` must be true
+* `T` must be callable with the provided cvref qualifiers and the provided argument types
+--
+
+### List In-Place Constructor
+
+```cpp
+template<class T, class U, class ...CArgs>
+explicit move_only_function( in_place_type_t<T>,
+                             std::initializer_list<U> il, CArgs&& ... args );
+```
+
+[horizontal]
+Effects:;; Constructs an object of type `T` using the provided initializer_list and args directly, storing it as the target Callable.
+Constraints:;;
++
+--
+* `is_constructible_v<T, std::initializer_list<U>&, CArgs...>` must be true
+* `T` must be callable with the provided cvref qualifiers and the provided argument types
+--
+
+### Move Constructor
+
+```cpp
+move_only_function( move_only_function&& f ) = default;
+```
+
+[horizontal]
+Effects::
+Tranfers ownership of the object managed by `f` to `*this`. After this operation completes, `f` is empty and manages no object.
+
+## Assignment
+
+### Move Assignment
+
+```cpp
+move_only_function& operator=( move_only_function&& rhs );
+```
+
+[horizontal]
+Effects:;; Releases the currently managed object and takes ownership of the object managed by `rhs`, if applicable.
+`rhs` is empty after move.
+
+### Null Assigment
+
+```cpp
+move_only_function& operator=( std::nullptr_t ) noexcept;
+```
+
+[horizontal]
+Effects:;; Releases the currently managed object, if applicable.
+
+### Callable Assignment
+
+```cpp
+template<class F> move_only_function& operator=( F&& f );
+```
+
+[horizontal]
+Effects:;; Releases the currently managed object and then does the equivalent of: `move_only_function(std::forward<F>(f)).swap(*this)`.
+
+## Utility
+
+### Null Equality
+
+```cpp
+friend bool operator==( move_only_function const& fn, std::nullptr_t ) noexcept;
+friend bool operator!=( move_only_function const& fn, std::nullptr_t ) noexcept;
+```
+
+[horizontal]
+Effects:;; Returns whether or not `fn` contains a target object.
+
+### Swap
+
+```cpp
+void swap( move_only_function& rhs ) noexcept;
+friend void swap( move_only_function& lhs, move_only_function& rhs ) noexcept;
+```
+
+[horizontal]
+Effects:;; Exchanges the managed objects.
+
+## Invocation
+
+### Boolean Conversion
+
+```cpp
+explicit operator bool() const noexcept;
+```
+
+[horizontal]
+Effects:;; Returns `true` if `*this` is managing an object, or `false` if `*this` is empty.
+
+### Call Operator
+
+```cpp
+R operator()( Args... args ) /* cv */ /* ref */ noexcept( /* noex */ );
+```
+
+[horizontal]
+Preconditions:;; `*this` currently manages an object.
+Effects:;; Invokes the underlying target object. Equivalent to:
++
+--
+```cpp
+return INVOKE<R>(static_cast<F inv-quals>(f), std::forward<Args>(args)...);
+```
+
+where `f` is the target object, and _inv-quals_ is defined by the standard:
+
+* If _ref_ is empty, let _inv-quals_ be _cv&_,
+* otherwise, let _inv-quals_ be _cv ref_.
+--

doc/compat/reference.adoc

@@ -7,6 +7,7 @@ https://www.boost.org/LICENSE_1_0.txt
 include::bind_back.adoc[]
 include::bind_front.adoc[]
 include::function_ref.adoc[]
+include::move_only_function.adoc[]
 include::integer_sequence.adoc[]
 include::invoke.adoc[]
 include::latch.adoc[]

include/boost/compat/type_traits.hpp

@@ -2,7 +2,7 @@
 #define BOOST_COMPAT_TYPE_TRAITS_HPP_INCLUDED
 
 // Copyright 2024 Peter Dimov
-// Copyright 2024 Christian Mazakas
+// Copyright 2024-2025 Christian Mazakas
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
 
@@ -11,10 +11,14 @@
 namespace boost {
 namespace compat {
 
+template<class T> using add_lvalue_reference_t = typename std::add_lvalue_reference<T>::type;
+template<class T> using add_rvalue_reference_t = typename std::add_rvalue_reference<T>::type;
+
 template<class T> using remove_const_t = typename std::remove_const<T>::type;
 template<class T> using remove_cv_t = typename std::remove_cv<T>::type;
 template<class T> using remove_reference_t = typename std::remove_reference<T>::type;
 template<class T> using remove_cvref_t = remove_cv_t< remove_reference_t<T> >;
+template<class T> using remove_pointer_t = typename std::remove_pointer<T>::type;
 
 template<class T> using decay_t = typename std::decay<T>::type;
 
@@ -35,6 +39,11 @@ template<class... T> using void_t = typename detail::make_void<T...>::type;
 
 template<class T> using add_const_t = typename std::add_const<T>::type;
 
+template<class T> struct type_identity
+{
+    using type = T;
+};
+
 } // namespace compat
 } // namespace boost
 

test/Jamfile

@@ -113,5 +113,7 @@ run function_ref_fn_noexcept_test.cpp ;
 run function_ref_mfn_noexcept_test.cpp ;
 run function_ref_obj_noexcept_test.cpp ;
 
+run move_only_function_test.cpp ;
+
 run to_array_lvalue_test.cpp ;
 run to_array_rvalue_test.cpp ;

test/move_only_function_test.cpp

@@ -0,0 +1,855 @@
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
+
+#if BOOST_WORKAROUND(BOOST_GCC, >= 7 * 10000 && BOOST_GCC < 8 * 10000)
+#   pragma GCC diagnostic push
+#   pragma GCC diagnostic ignored "-Wnoexcept-type"
+#endif
+
+#include <boost/compat/move_only_function.hpp>
+
+#include <boost/compat/invoke.hpp>
+
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+#include <functional>
+#include <memory>
+#include <type_traits>
+
+#if BOOST_WORKAROUND(BOOST_GCC, >= 13 * 10000)
+#   pragma GCC diagnostic push
+#   pragma GCC diagnostic ignored "-Wself-move"
+#elif defined(BOOST_CLANG)
+#   pragma clang diagnostic push
+#   pragma clang diagnostic ignored "-Wself-move"
+#endif
+
+using std::is_same;
+using std::is_constructible;
+using std::is_nothrow_constructible;
+
+using boost::compat::move_only_function;
+using boost::compat::in_place_type_t;
+// using std::move_only_function;
+// using std::in_place_type_t;
+using boost::compat::invoke_result_t;
+using boost::compat::is_invocable;
+using boost::compat::is_nothrow_invocable;
+
+template<class T>
+using add_const_t = typename std::add_const<T>::type;
+
+template<class T>
+constexpr add_const_t<T>& as_const_ref( T& t ) noexcept
+{
+    return t;
+}
+
+void func0() {}
+
+int func1()
+{
+    return 1;
+}
+
+int func2( int x )
+{
+    return x + 1;
+}
+
+int func3( std::unique_ptr<int> x )
+{
+    return *x + 1;
+}
+
+template<class T, class ...Args>
+std::unique_ptr<T> make_unique( Args&&... args )
+{
+    return std::unique_ptr<T>( new T( std::forward<Args>( args )... ) );
+}
+
+struct callable
+{
+    std::unique_ptr<int> p_ = make_unique<int>( 1 );
+
+    callable() = default;
+
+    callable( std::unique_ptr<int> p ): p_( std::move( p ) )
+    {
+    }
+
+    callable( std::initializer_list<int> il, int x, int y, int z )
+    {
+        int sum = 0;
+        for( auto const v : il )
+        {
+            sum += v;
+        }
+        sum += x;
+        sum += y;
+        sum += z;
+        p_ = make_unique<int>( sum );
+    }
+
+    callable( callable&& rhs ) noexcept
+    {
+        p_ = make_unique<int>( *rhs.p_ );
+    }
+
+    int operator()( int x )
+    {
+        return *p_ + x;
+    }
+};
+
+struct noex_callable
+{
+    std::unique_ptr<int> p_ = make_unique<int>( 1 );
+
+    noex_callable() = default;
+    noex_callable( noex_callable&& rhs ) noexcept
+    {
+        p_ = make_unique<int>( *rhs.p_ );
+    }
+
+    noex_callable( noex_callable const& )
+    {
+    }
+
+    int operator()( int x ) noexcept
+    {
+        return *p_ + x;
+    }
+};
+
+struct large_callable
+{
+    unsigned char padding[ 256 ] = {};
+    std::unique_ptr<int> p_ = make_unique<int>( 1 );
+
+    large_callable() = default;
+
+    large_callable( std::unique_ptr<int> p ): p_( std::move( p ) )
+    {
+    }
+
+    large_callable( large_callable&& rhs ) noexcept
+    {
+        p_ = make_unique<int>( *rhs.p_ );
+    }
+
+    int operator()( int x )
+    {
+        return *p_ + x;
+    }
+
+    int operator()( int x, int y )
+    {
+        return x + y;
+    }
+};
+
+struct person
+{
+    std::string name_;
+    int age_ = -1;
+    std::unique_ptr<int> p_ = make_unique<int>( 1 );
+
+    int age()
+    {
+        return age_;
+    }
+};
+
+static void test_call()
+{
+    {
+        move_only_function<int()> f1;
+        BOOST_TEST( !f1 );
+
+        move_only_function<int() const> f2;
+        BOOST_TEST( !f2 );
+    }
+
+    {
+        move_only_function<int()> f1( nullptr );
+        BOOST_TEST( !f1 );
+
+        move_only_function<int() const> f2( nullptr );
+        BOOST_TEST( !f2 );
+    }
+
+    {
+        move_only_function<void()> f1( func0 );
+        f1();
+        BOOST_TEST( f1 );
+
+        move_only_function<void() const> f2( func0 );
+        f2();
+        BOOST_TEST( f2 );
+    }
+
+    {
+        int ( *fp )() = [] { return 0; };
+
+        move_only_function<int()> f1( fp );
+        BOOST_TEST( f1 );
+        BOOST_TEST_EQ( f1(), 0 );
+        BOOST_TEST_EQ( std::move( f1() ), 0 );
+
+        move_only_function<int() const> f2( fp );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2(), 0 );
+        BOOST_TEST_EQ( std::move( f2() ), 0 );
+
+        fp = nullptr;
+        move_only_function<int() const> f3( fp );
+        BOOST_TEST_NOT( f3 );
+    }
+
+    {
+        struct declared;
+        enum class integer : int;
+
+        move_only_function<void(declared)> f1;
+        move_only_function<void(declared&)> f2;
+        move_only_function<void(declared&&)> f3;
+        move_only_function<void(integer)> f4;
+    }
+
+    {
+        move_only_function<int()> f1( func1 );
+        BOOST_TEST( f1 );
+        BOOST_TEST_EQ( f1(), 1 );
+        BOOST_TEST_EQ( std::move( f1() ), 1 );
+
+        move_only_function<int() const> f2( func1 );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2(), 1 );
+        BOOST_TEST_EQ( std::move( f2() ), 1 );
+    }
+
+    {
+        move_only_function<int( std::unique_ptr<int> )> fn( func3 );
+        BOOST_TEST_EQ( fn( make_unique<int>( 1 ) ), 2 );
+        BOOST_TEST_EQ( std::move( fn )( make_unique<int>( 1 ) ), 2 );
+
+        auto x = make_unique<int>( 1 );
+        BOOST_TEST( fn );
+        BOOST_TEST_EQ( fn( std::move( x ) ), 2 );
+    }
+
+    {
+        auto l = []() { return 1; };
+
+        move_only_function<int()> f1( l );
+        BOOST_TEST( f1 );
+        BOOST_TEST_EQ( f1(), 1 );
+        BOOST_TEST_EQ( std::move( f1 )(), 1 );
+
+        move_only_function<int() const> f2( l );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2(), 1 );
+        BOOST_TEST_EQ( as_const_ref( f2 )(), 1 );
+        BOOST_TEST_EQ( std::move( f2 )(), 1 );
+        BOOST_TEST_EQ( std::move( as_const_ref( f2 ) )(), 1 );
+    }
+
+    {
+        move_only_function<int()> f1( []() { return 1; } );
+        BOOST_TEST( f1 );
+        BOOST_TEST_EQ( f1(), 1 );
+        BOOST_TEST_EQ( std::move( f1 )(), 1 );
+
+        move_only_function<int() const> f2( []() { return 1; } );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2(), 1 );
+        BOOST_TEST_EQ( as_const_ref( f2 )(), 1 );
+        BOOST_TEST_EQ( std::move( f2 )(), 1 );
+        BOOST_TEST_EQ( std::move( as_const_ref( f2 ) )(), 1 );
+    }
+
+    {
+        auto l = []( int x ) { return x + 1; };
+
+        move_only_function<int( int )> f1( l );
+        BOOST_TEST( f1 );
+        BOOST_TEST_EQ( f1( 1 ), 2 );
+
+        move_only_function<int( int ) const> f2( l );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2( 1 ), 2 );
+    }
+
+    {
+        auto l = []( std::unique_ptr<int> x ) { return *x + 1; };
+        move_only_function<int( std::unique_ptr<int> )> f( std::move( l ) );
+        BOOST_TEST( f );
+        BOOST_TEST_EQ( f( make_unique<int>( 1 ) ), 2 );
+    }
+
+    {
+        auto p = make_unique<int>( 1 );
+        auto l = []( std::unique_ptr<int>& x ) { return *x + 1; };
+        move_only_function<int( std::unique_ptr<int>& )> f( l );
+        BOOST_TEST( f );
+        BOOST_TEST_EQ( f( p ), 2 );
+    }
+
+    {
+        int x = 1;
+        move_only_function<int( int )> f1( callable{} );
+        BOOST_TEST( f1 );
+        BOOST_TEST_EQ( f1( 1 ), 2);
+        BOOST_TEST_EQ( f1( x ), 2 );
+
+        int y = 2;
+        callable c;
+        move_only_function<int( int )> f2( std::move( c ) );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2( 2 ), 3 );
+        BOOST_TEST_EQ( f2( y ), 3 );
+    }
+
+    {
+        move_only_function<int( int, int )> f1( large_callable{} );
+        BOOST_TEST( f1 );
+        BOOST_TEST_EQ( f1( 1, 2 ), 3);
+
+        large_callable c;
+        move_only_function<int( int, int )> f2( std::move( c ) );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2( 1, 2 ), 3 );
+    }
+
+    {
+        move_only_function<int( int )> f1( in_place_type_t<callable>{}, make_unique<int>( 4321 ) );
+        BOOST_TEST_EQ( f1( 1234 ), 5555 );
+
+        move_only_function<int( int )> f2( in_place_type_t<large_callable>{}, make_unique<int>( 4321 ) );
+        BOOST_TEST_EQ( f2( 1234 ), 5555 );
+
+        move_only_function<int( int )> f3( in_place_type_t<int(*)( int )>{}, func2 );
+        BOOST_TEST_EQ( f3( 1233 ), 1234 );
+
+        move_only_function<int( int )> f4( in_place_type_t<int(*)( int )>{} );
+        BOOST_TEST( f4 != nullptr );
+
+        move_only_function<int( int )> f5( in_place_type_t<callable>{}, std::initializer_list<int>{ 1, 2, 3 }, 4, 5, 6 );
+        BOOST_TEST_EQ( f5( 7 ), 1 + 2 + 3 + 4 + 5 + 6 + 7 );
+    }
+
+    {
+        move_only_function<int()> f1( func1 );
+        move_only_function<int()> f2( std::move( f1 ) );
+
+        BOOST_TEST( !f1 );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2(), 1 );
+    }
+
+    {
+        move_only_function<int( int )> f1( callable{} );
+        move_only_function<int( int )> f2( std::move( f1 ) );
+
+        BOOST_TEST( !f1 );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2( 2 ), 3 );
+    }
+
+    {
+        move_only_function<int( int, int )> f1( large_callable{} );
+        move_only_function<int( int, int )> f2( std::move( f1 ) );
+
+        BOOST_TEST( !f1 );
+        BOOST_TEST( f2 );
+        BOOST_TEST_EQ( f2( 1, 2 ), 3 );
+    }
+
+    {
+        person p;
+        p.age_ = 35;
+
+        move_only_function<int( person& )> f1( &person::age_ );
+        BOOST_TEST_EQ( f1( p ), 35 );
+
+        p.age_ = 53;
+
+        move_only_function<int( person& )> f2( &person::age );
+        BOOST_TEST_EQ( f2( p ), 53 );
+
+        int person::*mp = nullptr;
+        move_only_function<int( person& )> f3( mp );
+        BOOST_TEST_NOT( f3 );
+
+        int (person::*mfp)() = nullptr;
+        move_only_function<int( person& )> f4( mfp );
+        BOOST_TEST_NOT( f4 );
+    }
+
+    {
+        struct tester
+        {
+            int operator()()
+            {
+                return 1;
+            }
+
+            int operator()() const
+            {
+                return 2;
+            }
+        };
+
+        tester t;
+
+        move_only_function<int()> f1( t );
+        move_only_function<int() const> f2( t );
+
+        BOOST_TEST_EQ( f1(), 1 );
+        BOOST_TEST_EQ( std::move( f1 )(), 1 );
+        BOOST_TEST_EQ( f2(), 2 );
+        BOOST_TEST_EQ( as_const_ref( f2 )(), 2 );
+        BOOST_TEST_EQ( std::move( as_const_ref( f2 ) )(), 2 );
+    }
+
+    {
+        struct tester
+        {
+            int operator()() noexcept
+            {
+                return 1;
+            }
+
+            int operator()() const noexcept
+            {
+                return 2;
+            }
+        };
+
+        tester t;
+
+        move_only_function<int() noexcept> f1( t );
+        move_only_function<int() const noexcept> f2( t );
+
+        BOOST_TEST_EQ( f1(), 1 );
+        BOOST_TEST_EQ( std::move( f1 )(), 1 );
+        BOOST_TEST_EQ( f2(), 2 );
+        BOOST_TEST_EQ( as_const_ref( f2 )(), 2 );
+        BOOST_TEST_EQ( std::move( as_const_ref( f2 ) )(), 2 );
+    }
+
+    {
+        struct tester
+        {
+            int operator()() &
+            {
+                return 1;
+            }
+
+            int operator()() &&
+            {
+                return 2;
+            }
+
+            int operator()() const&
+            {
+                return 3;
+            }
+
+            int operator()() const&&
+            {
+                return 4;
+            }
+        };
+
+        tester t;
+
+        move_only_function<int() &> f1( t );
+        move_only_function<int() &&> f2( t );
+        move_only_function<int() const&> f3( t );
+
+        BOOST_TEST_EQ( f1(), 1 );
+        BOOST_TEST_EQ( std::move( f2 )(), 2 );
+        BOOST_TEST_EQ( f3(), 3 );
+        BOOST_TEST_EQ( as_const_ref( f3 )(), 3 );
+
+#if !BOOST_WORKAROUND(BOOST_GCC, < 40900)
+
+        move_only_function<int() const&&> f4( t );
+        BOOST_TEST_EQ( std::move( f4 )(), 4 );
+        BOOST_TEST_EQ( std::move( as_const_ref( f4 ) )(), 4 );
+
+#endif
+    }
+
+    {
+        struct tester
+        {
+            int operator()() & noexcept
+            {
+                return 1;
+            }
+
+            int operator()() && noexcept
+            {
+                return 2;
+            }
+
+            int operator()() const& noexcept
+            {
+                return 3;
+            }
+
+            int operator()() const&& noexcept
+            {
+                return 4;
+            }
+        };
+
+        tester t;
+
+        move_only_function<int() &> f1( t );
+        move_only_function<int() &&> f2( t );
+        move_only_function<int() const&> f3( t );
+
+        BOOST_TEST_EQ( f1(), 1 );
+        BOOST_TEST_EQ( std::move( f2 )(), 2 );
+        BOOST_TEST_EQ( f3(), 3 );
+        BOOST_TEST_EQ( as_const_ref( f3 )(), 3 );
+
+#if !BOOST_WORKAROUND(BOOST_GCC, < 40900)
+
+        move_only_function<int() const&&> f4( t );
+        BOOST_TEST_EQ( std::move( f4 )(), 4 );
+        BOOST_TEST_EQ( std::move( as_const_ref( f4 ) )(), 4 );
+
+#endif
+    }
+
+    {
+        move_only_function<int( int )> f1( callable{} );
+        // f1 = std::move( f1 );
+        // BOOST_TEST_EQ( f1( 1233 ), 1234 );
+
+        move_only_function<int( int )> f2( large_callable{} );
+        f2 = std::move( f1 );
+        BOOST_TEST_EQ( f2( 1233 ), 1234 );
+        BOOST_TEST_NOT( f1 );
+
+        move_only_function<int( int )> f3( callable{} );
+        move_only_function<int( int )> f4( large_callable{} );
+        f3 = std::move( f4 );
+        BOOST_TEST_EQ( f3( 1233 ), 1234 );
+        BOOST_TEST_NOT( f4 );
+
+        move_only_function<int( int )> f5( callable{} );
+        f5 = nullptr;
+        BOOST_TEST_NOT( f5 );
+
+        move_only_function<int( int )> f6( large_callable{} );
+        f6 = nullptr;
+        BOOST_TEST_NOT( f6 );
+
+        move_only_function<int( int )> f7;
+        f7 = nullptr;
+        BOOST_TEST_NOT( f7 );
+
+        move_only_function<int( int )> f8( callable{} );
+        f8 = large_callable{};
+        BOOST_TEST_EQ( f8( 1233 ), 1234 );
+
+        move_only_function<int( int )> f9( large_callable{} );
+        f9 = callable{};
+        BOOST_TEST_EQ( f9( 1233 ), 1234 );
+
+        move_only_function<int( int )> f10;
+        f10 = callable{};
+        BOOST_TEST_EQ( f10( 1233 ), 1234 );
+
+        move_only_function<int( int )> f11;
+        f11 = large_callable{};
+        BOOST_TEST_EQ( f11( 1233 ), 1234 );
+    }
+
+    {
+        callable c1;
+        *c1.p_ = 1234;
+
+        large_callable c2;
+        *c2.p_ = 4321;
+
+        move_only_function<int( int )> f1( std::move( c1 ) );
+        move_only_function<int( int )> f2( std::move( c2 ) );
+
+        int x = 1;
+
+        BOOST_TEST_EQ( f1( x ), 1235 );
+        BOOST_TEST_EQ( f2( x ), 4322 );
+
+        swap( f1, f2 );
+
+        BOOST_TEST_EQ( f1( x ), 4322 );
+        BOOST_TEST_EQ( f2( x ), 1235 );
+
+        move_only_function<int( int )> f3( callable{} );
+        move_only_function<int( int )> f4;
+
+        swap( f3, f4 );
+        BOOST_TEST_NOT( f3 );
+        BOOST_TEST( f4 );
+
+        move_only_function<int( int )> f5;
+        move_only_function<int( int )> f6;
+
+        swap( f5, f6 );
+        BOOST_TEST_NOT( f5 );
+        BOOST_TEST_NOT( f6 );
+    }
+
+    {
+        struct throwing
+        {
+            static int x()
+            {
+                throw 1234;
+            }
+
+            int operator()()
+            {
+                throw 1234;
+            }
+        };
+
+        struct large_throwing
+        {
+            char padding[ 256 ] = {};
+
+            int operator()()
+            {
+                throw 1234;
+            }
+        };
+
+        move_only_function<int()> f1( &throwing::x );
+        move_only_function<int()> f2( throwing{} );
+        move_only_function<int()> f3( large_throwing{} );
+
+        BOOST_TEST_THROWS( f1(), int );
+        BOOST_TEST_THROWS( f2(), int );
+        BOOST_TEST_THROWS( f3(), int );
+    }
+}
+
+struct Q
+{
+    void operator()() const &;
+    void operator()() &&;
+};
+
+struct R
+{
+    void operator()() &;
+    void operator()() &&;
+};
+
+// These types are all small and nothrow move constructible
+struct F { void operator()(); };
+struct G { void operator()() const; };
+
+struct H
+{
+    H( int );
+    H( int, int ) noexcept;
+    void operator()() noexcept;
+};
+
+struct I
+{
+    I( int, const char* );
+    I( std::initializer_list<char> );
+    int operator()() const noexcept;
+};
+
+static void test_traits()
+{
+    // just copy the static assertions from libstdc++'s test suite, call.cc, cons.cc, conv.cc
+
+    // Check return types
+    BOOST_TEST_TRAIT_TRUE( ( is_same<void, invoke_result_t<move_only_function<void()>>> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_same<int, invoke_result_t<move_only_function<int()>>> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_same<int&, invoke_result_t<move_only_function<int&()>>> ) );
+
+    // With const qualifier
+    BOOST_TEST_TRAIT_FALSE( ( is_invocable< move_only_function<void()> const > ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_invocable< move_only_function<void()> const &> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const> > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const> &> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const> const > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const> const &> ) );
+
+    // With no ref-qualifier
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void()> > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void()> &> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const> > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const> &> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const> const > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const> const &> ) );
+
+    // With & ref-qualifier
+    BOOST_TEST_TRAIT_FALSE( ( is_invocable< move_only_function<void()&> > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void()&> &> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const&> > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const&> &> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const&> const > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const&> const &> ) );
+
+    // With && ref-qualifier
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void()&&> > ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_invocable< move_only_function<void()&&> &> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const&&> > ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_invocable< move_only_function<void() const&&> &> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_invocable< move_only_function<void() const&&> const > ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_invocable< move_only_function<void() const&&> const &> ) );
+
+    #if defined(__cpp_noexcept_function_type)
+
+    // With noexcept-specifier
+    BOOST_TEST_TRAIT_FALSE( ( is_nothrow_invocable< move_only_function<void()> > ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_nothrow_invocable< move_only_function<void() noexcept(false)> > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_invocable< move_only_function<void() noexcept> > ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_invocable< move_only_function<void()& noexcept>& > ) );
+
+    #endif
+
+    BOOST_TEST_TRAIT_TRUE( ( std::is_nothrow_default_constructible<move_only_function<void()>> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_constructible<move_only_function<void()>, std::nullptr_t> ) );
+    BOOST_TEST_TRAIT_TRUE( ( std::is_nothrow_move_constructible<move_only_function<void()>> ) );
+    BOOST_TEST_TRAIT_FALSE( ( std::is_copy_constructible<move_only_function<void()>> ) );
+
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, void()> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, void( & )()> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, void( * )()> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, int()> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, int( & )()> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, int( * )()> ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void()>, void( int )> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void(int)>, void( int )> ) );
+
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void( int )>, in_place_type_t<void(*)( int )>, void( int )> ) );
+
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, void() noexcept> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void() noexcept>, void() noexcept> ) );
+
+#if defined(__cpp_noexcept_function_type)
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void() noexcept>, void()> ) );
+#endif
+
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, Q> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void() const>, Q> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void() &>, Q> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void() const &>, Q> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void() &&>, Q> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void() const &&>, Q> ) );
+
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, R> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()&>, R> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()&&>, R> ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void() const>, R> ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void() const&>, R> ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void() const&&>, R> ) );
+
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_constructible<move_only_function<void()>, F> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_constructible<move_only_function<void()>, G> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_constructible<move_only_function<void() const>, G> ) );
+
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_constructible<move_only_function<void()>, H> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_constructible<move_only_function<void() noexcept>, H> ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_nothrow_constructible<move_only_function<void() noexcept >, in_place_type_t<H>, int> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_nothrow_constructible<move_only_function<void() noexcept>, in_place_type_t<H>, int, int> ) );
+
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, in_place_type_t<I>, int, const char*> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_constructible<move_only_function<void()>, in_place_type_t<I>, std::initializer_list<char>> ) );
+
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void()>, move_only_function<void() &>> ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void()>, move_only_function<void() &&>> ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void()&>, move_only_function<void() &&>> ) );
+    BOOST_TEST_TRAIT_FALSE( ( is_constructible<move_only_function<void() const>, move_only_function<void()>> ) );
+
+    using FuncType = int( int );
+
+    // Top level const qualifiers are ignored in function types, and decay
+    // is performed.
+    BOOST_TEST_TRAIT_TRUE( ( is_same<move_only_function<void( int const )>, move_only_function<void( int )>> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_same<move_only_function<void( int[ 2 ] )>, move_only_function<void( int* )>> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_same<move_only_function<void( int[] )>, move_only_function<void( int* )>> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_same<move_only_function<void(int const[ 5 ])>, move_only_function<void( int const* )>> ) );
+    BOOST_TEST_TRAIT_TRUE( ( is_same<move_only_function<void( FuncType )>, move_only_function<void( FuncType* )>> ) );
+}
+
+static void test_conv()
+{
+    {
+        noex_callable nt;
+
+        move_only_function<int( int ) noexcept> f1( std::move( nt ) );
+        move_only_function<int( int )> f2( std::move( f1 ) );
+        BOOST_TEST_EQ( f2( 1234 ), 1235 );
+    }
+
+    {
+        auto l = []( noex_callable const& c ) noexcept { return *c.p_ + 1234; };
+
+        noex_callable c;
+
+        move_only_function<int( noex_callable ) const noexcept> f1( l );
+        BOOST_TEST_EQ( f1( c ), 1235 );
+
+        move_only_function<int( noex_callable ) const> f2( std::move( f1 ) );
+        BOOST_TEST_EQ( f2( c ), 1235 );
+
+        move_only_function<int( noex_callable )> f3( std::move( f2 ) );
+        BOOST_TEST_EQ( f3( c ), 1235 );
+
+        move_only_function<int( noex_callable&& )> f4( std::move( f3 ) );
+        BOOST_TEST_EQ( f4( noex_callable{} ), 1235 );
+
+        move_only_function<int( noex_callable&& ) &&> f5( std::move( f4 ) );
+        BOOST_TEST_EQ( std::move( f5 )( noex_callable{} ), 1235 );
+
+        move_only_function<int( noex_callable&& )> f6( l );
+
+        move_only_function<int( noex_callable&& ) &> f7( std::move( f6 ) );
+        BOOST_TEST_EQ( f7( noex_callable{} ), 1235 );
+
+        // TODO: libstdc++ includes this test case but it seems like pedantically calling a `long(*)(Arg)` should
+        // be UB in the general sense. We need to confirm one way or another if this is something we need to support.
+        //
+        // move_only_function<int( noex_callable ) const noexcept> f8( l );
+        // move_only_function<long( noex_callable ) const noexcept> f9( std::move( f8 ) );
+        // BOOST_TEST_EQ( f9( noex_callable{} ), 1235 );
+    }
+
+    {
+        move_only_function<int( long ) const noexcept> e;
+        BOOST_TEST( e == nullptr );
+
+        move_only_function<int( long ) const> e2( std::move( e ) );
+        BOOST_TEST( e2 == nullptr );
+        e2 = std::move( e );
+        BOOST_TEST( e2 == nullptr );
+
+        move_only_function<int( long )> e3( std::move( e2 ) );
+        BOOST_TEST( e3 == nullptr );
+    }
+}
+
+int main()
+{
+    test_call();
+    test_traits();
+    test_conv();
+
+    return boost::report_errors();
+}