g++ 4.7 doesn't have std::is_trivially_destructible

Add "cxxstd" json field. The "cxxstd" json field is being added to ea…

.github/workflows/ci.yml

@@ -0,0 +1,201 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - develop
+      - feature/**
+
+env:
+  UBSAN_OPTIONS: print_stacktrace=1
+
+jobs:
+  posix:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - toolset: gcc-4.7
+            cxxstd: "03,11"
+            os: ubuntu-16.04
+            install: g++-4.7
+          - toolset: gcc-4.8
+            cxxstd: "03,11"
+            os: ubuntu-16.04
+            install: g++-4.8
+          - toolset: gcc-4.9
+            cxxstd: "03,11"
+            os: ubuntu-16.04
+            install: g++-4.9
+          - toolset: gcc-5
+            cxxstd: "03,11,14,1z"
+            os: ubuntu-16.04
+          - toolset: gcc-6
+            cxxstd: "03,11,14,1z"
+            os: ubuntu-16.04
+            install: g++-6
+          - toolset: gcc-7
+            cxxstd: "03,11,14,17"
+            os: ubuntu-18.04
+          - toolset: gcc-8
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-18.04
+          - toolset: gcc-9
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-18.04
+          - toolset: gcc-10
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-18.04
+          - toolset: clang
+            compiler: clang++-3.5
+            cxxstd: "03,11,14"
+            os: ubuntu-16.04
+            install: clang-3.5
+          - toolset: clang
+            compiler: clang++-3.6
+            cxxstd: "03,11,14"
+            os: ubuntu-16.04
+            install: clang-3.6
+          - toolset: clang
+            compiler: clang++-3.7
+            cxxstd: "03,11,14"
+            os: ubuntu-16.04
+            install: clang-3.7
+          - toolset: clang
+            compiler: clang++-3.8
+            cxxstd: "03,11,14"
+            os: ubuntu-16.04
+            install: clang-3.8
+          - toolset: clang
+            compiler: clang++-3.9
+            cxxstd: "03,11,14"
+            os: ubuntu-16.04
+            install: clang-3.9
+          - toolset: clang
+            compiler: clang++-4.0
+            cxxstd: "03,11,14"
+            os: ubuntu-16.04
+            install: clang-4.0
+          - toolset: clang
+            compiler: clang++-5.0
+            cxxstd: "03,11,14,1z"
+            os: ubuntu-16.04
+            install: clang-5.0
+          - toolset: clang
+            compiler: clang++-6.0
+            cxxstd: "03,11,14,17"
+            os: ubuntu-18.04
+          - toolset: clang
+            compiler: clang++-7
+            cxxstd: "03,11,14,17"
+            os: ubuntu-18.04
+            install: clang-7
+          - toolset: clang
+            compiler: clang++-8
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-20.04
+          - toolset: clang
+            compiler: clang++-9
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-20.04
+          - toolset: clang
+            compiler: clang++-10
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-20.04
+          - toolset: clang
+            cxxstd: "03,11,14,17,2a"
+            os: macos-10.15
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install packages
+        if: matrix.install
+        run: sudo apt install ${{matrix.install}}
+
+      - name: Setup Boost
+        run: |
+          echo GITHUB_REPOSITORY: $GITHUB_REPOSITORY
+          LIBRARY=${GITHUB_REPOSITORY#*/}
+          echo LIBRARY: $LIBRARY
+          echo "LIBRARY=$LIBRARY" >> $GITHUB_ENV
+          echo GITHUB_BASE_REF: $GITHUB_BASE_REF
+          echo GITHUB_REF: $GITHUB_REF
+          REF=${GITHUB_BASE_REF:-$GITHUB_REF}
+          REF=${REF#refs/heads/}
+          echo REF: $REF
+          BOOST_BRANCH=develop && [ "$REF" == "master" ] && BOOST_BRANCH=master || true
+          echo BOOST_BRANCH: $BOOST_BRANCH
+          cd ..
+          git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          cp -r $GITHUB_WORKSPACE/* libs/$LIBRARY
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" $LIBRARY
+          ./bootstrap.sh
+          ./b2 -d0 headers
+
+      - name: Create user-config.jam
+        if: matrix.compiler
+        run: |
+          echo "using ${{matrix.toolset}} : : ${{matrix.compiler}} ;" > ~/user-config.jam
+
+      - name: Run tests
+        run: |
+          cd ../boost-root
+          ./b2 -j3 libs/$LIBRARY/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} variant=debug,release
+
+  windows:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - toolset: msvc-14.1
+            cxxstd: "14,17,latest"
+            addrmd: 32,64
+            os: windows-2016
+          - toolset: msvc-14.2
+            cxxstd: "14,17,latest"
+            addrmd: 32,64
+            os: windows-2019
+          - toolset: gcc
+            cxxstd: "03,11,14,17,2a"
+            addrmd: 64
+            os: windows-2019
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup Boost
+        shell: cmd
+        run: |
+          echo GITHUB_REPOSITORY: %GITHUB_REPOSITORY%
+          for /f %%i in ("%GITHUB_REPOSITORY%") do set LIBRARY=%%~nxi
+          echo LIBRARY: %LIBRARY%
+          echo LIBRARY=%LIBRARY%>>%GITHUB_ENV%
+          echo GITHUB_BASE_REF: %GITHUB_BASE_REF%
+          echo GITHUB_REF: %GITHUB_REF%
+          if "%GITHUB_BASE_REF%" == "" set GITHUB_BASE_REF=%GITHUB_REF%
+          set BOOST_BRANCH=develop
+          for /f %%i in ("%GITHUB_BASE_REF%") do if "%%~nxi" == "master" set BOOST_BRANCH=master
+          echo BOOST_BRANCH: %BOOST_BRANCH%
+          cd ..
+          git clone -b %BOOST_BRANCH% --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          xcopy /s /e /q %GITHUB_WORKSPACE% libs\%LIBRARY%\
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" %LIBRARY%
+          cmd /c bootstrap
+          b2 -d0 headers
+
+      - name: Run tests
+        shell: cmd
+        run: |
+          cd ../boost-root
+          b2 -j3 libs/%LIBRARY%/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} address-model=${{matrix.addrmd}} variant=debug,release

.travis.yml

@@ -4,8 +4,6 @@
 
 language: cpp
 
-sudo: false
-
 dist: xenial
 
 branches:
@@ -25,8 +23,14 @@ matrix:
 
   include:
     - os: linux
-      compiler: g++
-      env: TOOLSET=gcc COMPILER=g++ CXXSTD=11
+      compiler: g++-4.8
+      env: TOOLSET=gcc COMPILER=g++-4.8 CXXSTD=11
+      addons:
+        apt:
+          packages:
+            - g++-4.8
+          sources:
+            - ubuntu-toolchain-r-test
 
     - os: linux
       compiler: g++-4.9
@@ -88,6 +92,17 @@ matrix:
           sources:
             - ubuntu-toolchain-r-test
 
+    - os: linux
+      dist: bionic
+      compiler: g++-10
+      env: TOOLSET=gcc COMPILER=g++-10 CXXSTD=11,14,17,2a
+      addons:
+        apt:
+          packages:
+            - g++-10
+          sources:
+            - ubuntu-toolchain-r-test
+
     - os: linux
       compiler: g++-8
       env: UBSAN=1 TOOLSET=gcc COMPILER=g++-8 CXXSTD=11,14,17,2a UBSAN_OPTIONS=print_stacktrace=1 LINKFLAGS=-fuse-ld=gold
@@ -98,6 +113,11 @@ matrix:
           sources:
             - ubuntu-toolchain-r-test
 
+    - os: linux
+      dist: trusty
+      compiler: clang++
+      env: DIST=trusty TOOLSET=clang COMPILER=clang++ CXXSTD=11,14,1z
+
     - os: linux
       compiler: clang++-3.5
       env: TOOLSET=clang COMPILER=clang++-3.5 CXXSTD=11,14,1z
@@ -214,6 +234,19 @@ matrix:
             - sourceline: 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-9 main'
               key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
 
+    - os: linux
+      dist: xenial
+      compiler: clang++-10
+      env: TOOLSET=clang COMPILER=clang++-10 CXXSTD=11,14,17,2a
+      addons:
+        apt:
+          packages:
+            - clang-10
+          sources:
+            - ubuntu-toolchain-r-test
+            - sourceline: 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-10 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+
     - os: linux
       compiler: clang++-8
       env: UBSAN=1 TOOLSET=clang COMPILER=clang++-8 CXXSTD=11,14,17,2a UBSAN_OPTIONS=print_stacktrace=1
@@ -259,7 +292,6 @@ matrix:
         - ctest --output-on-failure -R boost_variant2
 
     - os: linux
-      compiler: g++
       env: CMAKE_SUBDIR_TEST=1
       install:
         - BOOST_BRANCH=develop && [ "$TRAVIS_BRANCH" == "master" ] && BOOST_BRANCH=master || true
@@ -276,8 +308,9 @@ matrix:
     - os: linux
       env: CMAKE_INSTALL_TEST=1
       script:
+        - pip install --user cmake
         - mkdir __build__ && cd __build__
-        - cmake -DBOOST_ENABLE_CMAKE=1 -DBoost_VERBOSE=1 -DBOOST_INCLUDE_LIBRARIES="variant2;config;mp11" -DCMAKE_INSTALL_PREFIX=~/.local ..
+        - cmake -DBOOST_ENABLE_CMAKE=1 -DBoost_VERBOSE=1 -DBOOST_INCLUDE_LIBRARIES=variant2 -DCMAKE_INSTALL_PREFIX=~/.local ..
         - cmake --build . --target install
         - cd ../libs/variant2/test/cmake_install_test && mkdir __build__ && cd __build__
         - cmake -DCMAKE_INSTALL_PREFIX=~/.local ..

CMakeLists.txt

@@ -17,13 +17,6 @@ target_link_libraries(boost_variant2
     Boost::mp11
 )
 
-if(BOOST_SUPERPROJECT_VERSION)
-
-  include(BoostInstall)
-  boost_install(TARGETS boost_variant2 HEADER_DIRECTORY include/)
-
-endif()
-
 if(BUILD_TESTING)
 
   add_subdirectory(test)

appveyor.yml

@@ -1,4 +1,4 @@
-# Copyright 2016-2018 Peter Dimov
+# Copyright 2016-2020 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
 
@@ -21,6 +21,14 @@ environment:
       TOOLSET: msvc-14.1
       ADDRMD: 32,64
       CXXSTD: 14,17
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      TOOLSET: clang-win
+      ADDRMD: 64
+      CXXSTD: 14,17
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      TOOLSET: msvc-14.2
+      ADDRMD: 32,64
+      CXXSTD: 14,17
 
 install:
   - set BOOST_BRANCH=develop
@@ -28,8 +36,6 @@ install:
   - cd ..
   - git clone -b %BOOST_BRANCH% --depth 1 https://github.com/boostorg/boost.git boost-root
   - cd boost-root
-  - git submodule update --init tools/build
-  - git submodule update --init libs/config
   - git submodule update --init tools/boostdep
   - xcopy /s /e /q %APPVEYOR_BUILD_FOLDER% libs\variant2\
   - python tools/boostdep/depinst/depinst.py variant2
@@ -41,4 +47,4 @@ build: off
 test_script:
   - if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
   - if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
-  - b2 libs/variant2/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release
+  - b2 -j3 libs/variant2/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release

doc/variant2/changelog.adoc

@@ -1,5 +1,5 @@
 ////
-Copyright 2019 Peter Dimov
+Copyright 2019, 2020 Peter Dimov
 
 Distributed under the Boost Software License, Version 1.0.
 
@@ -11,6 +11,19 @@ http://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix: changelog_
 
+## Changes in 1.74.0
+
+* Added support for derived types in `visit`
+* Improved compilation performance for many (hundreds of) alternatives.
+* Added support for `visit<R>`
+
+## Changes in 1.73.0
+
+* Added support for `std::hash`, `boost::hash`.
+* `variant<T...>` is now trivial when all types in `T...` are trivial.
+  This improves performance by enabling it to be passed to, and returned
+  from, functions in registers.
+
 ## Changes in 1.71.0
 
 After the Boost formal review, the implementation has been

doc/variant2/design.adoc

@@ -169,8 +169,6 @@ The main differences between this implementation and `std::variant` are:
   `variant<int, float>` is provided as the member function `subset<U...>`.
   (This operation can throw if the current state of the variant cannot be
   represented.)
-* `variant<T...>` is not (yet) trivial when all contained types are trivial,
-   as mandated by {cpp}17.
 * The {cpp}20 additions and changes to `std::variant` have not yet been
   implemented.
 

doc/variant2/reference.adoc

@@ -134,7 +134,7 @@ template<class... T>
 
 // visit
 
-template<class F, class... V>
+template<class R = /*unspecified*/, class F, class... V>
   constexpr /*see below*/ visit(F&& f, V&&... v);
 
 // monostate
@@ -838,7 +838,7 @@ Returns: ::
 ### visit
 
 ```
-template<class F, class... V>
+template<class R = /*unspecified*/, class F, class... V>
   constexpr /*see below*/ visit(F&& f, V&&... v);
 ```
 [none]
@@ -846,6 +846,10 @@ template<class F, class... V>
 +
 Returns: :: `std::forward<F>(f)(get<I>(std::forward<V>(v))...)`, where
   `I...` is `v.index()...`.
+Remarks: :: If `R` is given explicitly, as in `visit<int>`, the return
+  type is `R`. Otherwise, it's deduced from `F`. All possible applications
+  of `F` to the variant alternatives must have the same return type for
+  this deduction to succeed.
 
 ### swap
 

include/boost/variant2/variant.hpp

@@ -18,12 +18,14 @@
 #endif
 #include <boost/config.hpp>
 #include <boost/detail/workaround.hpp>
+#include <boost/cstdint.hpp>
 #include <cstddef>
 #include <type_traits>
 #include <exception>
 #include <cassert>
 #include <initializer_list>
 #include <utility>
+#include <functional> // std::hash
 
 //
 
@@ -502,11 +504,23 @@ using std::is_trivially_move_assignable;
 
 #endif
 
+#if defined( BOOST_LIBSTDCXX_VERSION ) && BOOST_LIBSTDCXX_VERSION < 40800
+
+template<class T> struct is_trivially_destructible: std::has_trivial_destructor<T>
+{
+};
+
+#else
+
+using std::is_trivially_destructible;
+
+#endif
+
 // variant_storage
 
 template<class D, class... T> union variant_storage_impl;
 
-template<class... T> using variant_storage = variant_storage_impl<mp11::mp_all<std::is_trivially_destructible<T>...>, T...>;
+template<class... T> using variant_storage = variant_storage_impl<mp11::mp_all<detail::is_trivially_destructible<T>...>, T...>;
 
 template<class D> union variant_storage_impl<D>
 {
@@ -547,6 +561,88 @@ template<class T1, class... T> union variant_storage_impl<mp11::mp_false, T1, T.
     template<std::size_t I> constexpr mp11::mp_at_c<mp11::mp_list<T...>, I-1> const& get( mp11::mp_size_t<I> ) const noexcept { return rest_.get( mp11::mp_size_t<I-1>() ); }
 };
 
+template<class T0, class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8, class T9, class... T> union variant_storage_impl<mp11::mp_false, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T...>
+{
+    T0 t0_;
+    T1 t1_;
+    T2 t2_;
+    T3 t3_;
+    T4 t4_;
+    T5 t5_;
+    T6 t6_;
+    T7 t7_;
+    T8 t8_;
+    T9 t9_;
+
+    variant_storage<T...> rest_;
+
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): t0_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<1>, A&&... a ): t1_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<2>, A&&... a ): t2_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<3>, A&&... a ): t3_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<4>, A&&... a ): t4_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<5>, A&&... a ): t5_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<6>, A&&... a ): t6_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<7>, A&&... a ): t7_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<8>, A&&... a ): t8_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<9>, A&&... a ): t9_( std::forward<A>(a)... ) {}
+
+    template<std::size_t I, class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-10>(), std::forward<A>(a)... ) {}
+
+    ~variant_storage_impl()
+    {
+    }
+
+    template<class... A> void emplace( mp11::mp_size_t<0>, A&&... a ) { ::new( &t0_ ) T0( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<1>, A&&... a ) { ::new( &t1_ ) T1( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<2>, A&&... a ) { ::new( &t2_ ) T2( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<3>, A&&... a ) { ::new( &t3_ ) T3( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<4>, A&&... a ) { ::new( &t4_ ) T4( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<5>, A&&... a ) { ::new( &t5_ ) T5( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<6>, A&&... a ) { ::new( &t6_ ) T6( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<7>, A&&... a ) { ::new( &t7_ ) T7( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<8>, A&&... a ) { ::new( &t8_ ) T8( std::forward<A>(a)... ); }
+    template<class... A> void emplace( mp11::mp_size_t<9>, A&&... a ) { ::new( &t9_ ) T9( std::forward<A>(a)... ); }
+
+    template<std::size_t I, class... A> void emplace( mp11::mp_size_t<I>, A&&... a )
+    {
+        rest_.emplace( mp11::mp_size_t<I-10>(), std::forward<A>(a)... );
+    }
+
+    BOOST_CXX14_CONSTEXPR T0& get( mp11::mp_size_t<0> ) noexcept { return t0_; }
+    constexpr T0 const& get( mp11::mp_size_t<0> ) const noexcept { return t0_; }
+
+    BOOST_CXX14_CONSTEXPR T1& get( mp11::mp_size_t<1> ) noexcept { return t1_; }
+    constexpr T1 const& get( mp11::mp_size_t<1> ) const noexcept { return t1_; }
+
+    BOOST_CXX14_CONSTEXPR T2& get( mp11::mp_size_t<2> ) noexcept { return t2_; }
+    constexpr T2 const& get( mp11::mp_size_t<2> ) const noexcept { return t2_; }
+
+    BOOST_CXX14_CONSTEXPR T3& get( mp11::mp_size_t<3> ) noexcept { return t3_; }
+    constexpr T3 const& get( mp11::mp_size_t<3> ) const noexcept { return t3_; }
+
+    BOOST_CXX14_CONSTEXPR T4& get( mp11::mp_size_t<4> ) noexcept { return t4_; }
+    constexpr T4 const& get( mp11::mp_size_t<4> ) const noexcept { return t4_; }
+
+    BOOST_CXX14_CONSTEXPR T5& get( mp11::mp_size_t<5> ) noexcept { return t5_; }
+    constexpr T5 const& get( mp11::mp_size_t<5> ) const noexcept { return t5_; }
+
+    BOOST_CXX14_CONSTEXPR T6& get( mp11::mp_size_t<6> ) noexcept { return t6_; }
+    constexpr T6 const& get( mp11::mp_size_t<6> ) const noexcept { return t6_; }
+
+    BOOST_CXX14_CONSTEXPR T7& get( mp11::mp_size_t<7> ) noexcept { return t7_; }
+    constexpr T7 const& get( mp11::mp_size_t<7> ) const noexcept { return t7_; }
+
+    BOOST_CXX14_CONSTEXPR T8& get( mp11::mp_size_t<8> ) noexcept { return t8_; }
+    constexpr T8 const& get( mp11::mp_size_t<8> ) const noexcept { return t8_; }
+
+    BOOST_CXX14_CONSTEXPR T9& get( mp11::mp_size_t<9> ) noexcept { return t9_; }
+    constexpr T9 const& get( mp11::mp_size_t<9> ) const noexcept { return t9_; }
+
+    template<std::size_t I> BOOST_CXX14_CONSTEXPR mp11::mp_at_c<mp11::mp_list<T...>, I-10>& get( mp11::mp_size_t<I> ) noexcept { return rest_.get( mp11::mp_size_t<I-10>() ); }
+    template<std::size_t I> constexpr mp11::mp_at_c<mp11::mp_list<T...>, I-10> const& get( mp11::mp_size_t<I> ) const noexcept { return rest_.get( mp11::mp_size_t<I-10>() ); }
+};
+
 // all trivially destructible
 template<class T1, class... T> union variant_storage_impl<mp11::mp_true, T1, T...>
 {
@@ -588,6 +684,105 @@ template<class T1, class... T> union variant_storage_impl<mp11::mp_true, T1, T..
     template<std::size_t I> constexpr mp11::mp_at_c<mp11::mp_list<T...>, I-1> const& get( mp11::mp_size_t<I> ) const noexcept { return rest_.get( mp11::mp_size_t<I-1>() ); }
 };
 
+template<class T0, class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8, class T9, class... T> union variant_storage_impl<mp11::mp_true, T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T...>
+{
+    T0 t0_;
+    T1 t1_;
+    T2 t2_;
+    T3 t3_;
+    T4 t4_;
+    T5 t5_;
+    T6 t6_;
+    T7 t7_;
+    T8 t8_;
+    T9 t9_;
+
+    variant_storage<T...> rest_;
+
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): t0_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<1>, A&&... a ): t1_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<2>, A&&... a ): t2_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<3>, A&&... a ): t3_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<4>, A&&... a ): t4_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<5>, A&&... a ): t5_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<6>, A&&... a ): t6_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<7>, A&&... a ): t7_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<8>, A&&... a ): t8_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<9>, A&&... a ): t9_( std::forward<A>(a)... ) {}
+
+    template<std::size_t I, class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-10>(), std::forward<A>(a)... ) {}
+
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<0>, A&&... a ) { ::new( &t0_ ) T0( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<1>, A&&... a ) { ::new( &t1_ ) T1( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<2>, A&&... a ) { ::new( &t2_ ) T2( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<3>, A&&... a ) { ::new( &t3_ ) T3( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<4>, A&&... a ) { ::new( &t4_ ) T4( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<5>, A&&... a ) { ::new( &t5_ ) T5( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<6>, A&&... a ) { ::new( &t6_ ) T6( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<7>, A&&... a ) { ::new( &t7_ ) T7( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<8>, A&&... a ) { ::new( &t8_ ) T8( std::forward<A>(a)... ); }
+    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<9>, A&&... a ) { ::new( &t9_ ) T9( std::forward<A>(a)... ); }
+
+    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<I>, A&&... a )
+    {
+        rest_.emplace( mp11::mp_size_t<I-10>(), std::forward<A>(a)... );
+    }
+
+    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_true, mp11::mp_size_t<I>, A&&... a )
+    {
+        *this = variant_storage_impl( mp11::mp_size_t<I>(), std::forward<A>(a)... );
+    }
+
+    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<I>, A&&... a )
+    {
+        this->emplace_impl( mp11::mp_all<
+            detail::is_trivially_move_assignable<T0>,
+            detail::is_trivially_move_assignable<T1>,
+            detail::is_trivially_move_assignable<T2>,
+            detail::is_trivially_move_assignable<T3>,
+            detail::is_trivially_move_assignable<T4>,
+            detail::is_trivially_move_assignable<T5>,
+            detail::is_trivially_move_assignable<T6>,
+            detail::is_trivially_move_assignable<T7>,
+            detail::is_trivially_move_assignable<T8>,
+            detail::is_trivially_move_assignable<T9>,
+            detail::is_trivially_move_assignable<T>...>(), mp11::mp_size_t<I>(), std::forward<A>(a)... );
+    }
+
+    BOOST_CXX14_CONSTEXPR T0& get( mp11::mp_size_t<0> ) noexcept { return t0_; }
+    constexpr T0 const& get( mp11::mp_size_t<0> ) const noexcept { return t0_; }
+
+    BOOST_CXX14_CONSTEXPR T1& get( mp11::mp_size_t<1> ) noexcept { return t1_; }
+    constexpr T1 const& get( mp11::mp_size_t<1> ) const noexcept { return t1_; }
+
+    BOOST_CXX14_CONSTEXPR T2& get( mp11::mp_size_t<2> ) noexcept { return t2_; }
+    constexpr T2 const& get( mp11::mp_size_t<2> ) const noexcept { return t2_; }
+
+    BOOST_CXX14_CONSTEXPR T3& get( mp11::mp_size_t<3> ) noexcept { return t3_; }
+    constexpr T3 const& get( mp11::mp_size_t<3> ) const noexcept { return t3_; }
+
+    BOOST_CXX14_CONSTEXPR T4& get( mp11::mp_size_t<4> ) noexcept { return t4_; }
+    constexpr T4 const& get( mp11::mp_size_t<4> ) const noexcept { return t4_; }
+
+    BOOST_CXX14_CONSTEXPR T5& get( mp11::mp_size_t<5> ) noexcept { return t5_; }
+    constexpr T5 const& get( mp11::mp_size_t<5> ) const noexcept { return t5_; }
+
+    BOOST_CXX14_CONSTEXPR T6& get( mp11::mp_size_t<6> ) noexcept { return t6_; }
+    constexpr T6 const& get( mp11::mp_size_t<6> ) const noexcept { return t6_; }
+
+    BOOST_CXX14_CONSTEXPR T7& get( mp11::mp_size_t<7> ) noexcept { return t7_; }
+    constexpr T7 const& get( mp11::mp_size_t<7> ) const noexcept { return t7_; }
+
+    BOOST_CXX14_CONSTEXPR T8& get( mp11::mp_size_t<8> ) noexcept { return t8_; }
+    constexpr T8 const& get( mp11::mp_size_t<8> ) const noexcept { return t8_; }
+
+    BOOST_CXX14_CONSTEXPR T9& get( mp11::mp_size_t<9> ) noexcept { return t9_; }
+    constexpr T9 const& get( mp11::mp_size_t<9> ) const noexcept { return t9_; }
+
+    template<std::size_t I> BOOST_CXX14_CONSTEXPR mp11::mp_at_c<mp11::mp_list<T...>, I-10>& get( mp11::mp_size_t<I> ) noexcept { return rest_.get( mp11::mp_size_t<I-10>() ); }
+    template<std::size_t I> constexpr mp11::mp_at_c<mp11::mp_list<T...>, I-10> const& get( mp11::mp_size_t<I> ) const noexcept { return rest_.get( mp11::mp_size_t<I-10>() ); }
+};
+
 // resolve_overload_*
 
 template<class... T> struct overload;
@@ -624,7 +819,7 @@ template<class U, class... T> using resolve_overload_index = mp11::mp_find<mp11:
 // variant_base
 
 template<bool is_trivially_destructible, bool is_single_buffered, class... T> struct variant_base_impl;
-template<class... T> using variant_base = variant_base_impl<mp11::mp_all<std::is_trivially_destructible<T>...>::value, mp11::mp_all<std::is_nothrow_move_constructible<T>...>::value, T...>;
+template<class... T> using variant_base = variant_base_impl<mp11::mp_all<detail::is_trivially_destructible<T>...>::value, mp11::mp_all<std::is_nothrow_move_constructible<T>...>::value, T...>;
 
 struct none {};
 
@@ -1050,20 +1245,317 @@ template<class T> struct is_nothrow_swappable: mp11::mp_valid<det2::is_nothrow_s
 
 #endif
 
+// variant_cc_base
+
+template<bool CopyConstructible, bool TriviallyCopyConstructible, class... T> struct variant_cc_base_impl;
+
+template<class... T> using variant_cc_base = variant_cc_base_impl<
+    mp11::mp_all<std::is_copy_constructible<T>...>::value,
+    mp11::mp_all<detail::is_trivially_copy_constructible<T>...>::value,
+    T...>;
+
+template<class... T> struct variant_cc_base_impl<true, true, T...>: public variant_base<T...>
+{
+    using variant_base = detail::variant_base<T...>;
+    using variant_base::variant_base;
+
+    variant_cc_base_impl() = default;
+    variant_cc_base_impl( variant_cc_base_impl const& ) = default;
+    variant_cc_base_impl( variant_cc_base_impl && ) = default;
+    variant_cc_base_impl& operator=( variant_cc_base_impl const& ) = default;
+    variant_cc_base_impl& operator=( variant_cc_base_impl && ) = default;
+};
+
+template<bool B, class... T> struct variant_cc_base_impl<false, B, T...>: public variant_base<T...>
+{
+    using variant_base = detail::variant_base<T...>;
+    using variant_base::variant_base;
+
+    variant_cc_base_impl() = default;
+    variant_cc_base_impl( variant_cc_base_impl const& ) = delete;
+    variant_cc_base_impl( variant_cc_base_impl && ) = default;
+    variant_cc_base_impl& operator=( variant_cc_base_impl const& ) = default;
+    variant_cc_base_impl& operator=( variant_cc_base_impl && ) = default;
+};
+
+template<class... T> struct variant_cc_base_impl<true, false, T...>: public variant_base<T...>
+{
+    using variant_base = detail::variant_base<T...>;
+    using variant_base::variant_base;
+
+public:
+
+    // constructors
+
+    variant_cc_base_impl() = default;
+
+    // copy constructor
+
+private:
+
+    struct L1
+    {
+        variant_base * this_;
+        variant_base const & r;
+
+        template<class I> void operator()( I i ) const
+        {
+            this_->_replace( i, r._get_impl( i ) );
+        }
+    };
+
+public:
+
+    variant_cc_base_impl( variant_cc_base_impl const& r )
+        noexcept( mp11::mp_all<std::is_nothrow_copy_constructible<T>...>::value )
+        : variant_base()
+    {
+        mp11::mp_with_index<sizeof...(T)>( r.index(), L1{ this, r } );
+    }
+
+    // move constructor
+
+    variant_cc_base_impl( variant_cc_base_impl && ) = default;
+
+    // assignment
+
+    variant_cc_base_impl& operator=( variant_cc_base_impl const & ) = default;
+    variant_cc_base_impl& operator=( variant_cc_base_impl && ) = default;
+};
+
+// variant_ca_base
+
+template<bool CopyAssignable, bool TriviallyCopyAssignable, class... T> struct variant_ca_base_impl;
+
+template<class... T> using variant_ca_base = variant_ca_base_impl<
+    mp11::mp_all<std::is_copy_constructible<T>..., std::is_copy_assignable<T>...>::value,
+    mp11::mp_all<detail::is_trivially_destructible<T>..., detail::is_trivially_copy_constructible<T>..., detail::is_trivially_copy_assignable<T>...>::value,
+    T...>;
+
+template<class... T> struct variant_ca_base_impl<true, true, T...>: public variant_cc_base<T...>
+{
+    using variant_base = detail::variant_cc_base<T...>;
+    using variant_base::variant_base;
+
+    variant_ca_base_impl() = default;
+    variant_ca_base_impl( variant_ca_base_impl const& ) = default;
+    variant_ca_base_impl( variant_ca_base_impl && ) = default;
+    variant_ca_base_impl& operator=( variant_ca_base_impl const& ) = default;
+    variant_ca_base_impl& operator=( variant_ca_base_impl && ) = default;
+};
+
+template<bool B, class... T> struct variant_ca_base_impl<false, B, T...>: public variant_cc_base<T...>
+{
+    using variant_base = detail::variant_cc_base<T...>;
+    using variant_base::variant_base;
+
+    variant_ca_base_impl() = default;
+    variant_ca_base_impl( variant_ca_base_impl const& ) = default;
+    variant_ca_base_impl( variant_ca_base_impl && ) = default;
+    variant_ca_base_impl& operator=( variant_ca_base_impl const& ) = delete;
+    variant_ca_base_impl& operator=( variant_ca_base_impl && ) = default;
+};
+
+template<class... T> struct variant_ca_base_impl<true, false, T...>: public variant_cc_base<T...>
+{
+    using variant_base = detail::variant_cc_base<T...>;
+    using variant_base::variant_base;
+
+public:
+
+    // constructors
+
+    variant_ca_base_impl() = default;
+    variant_ca_base_impl( variant_ca_base_impl const& ) = default;
+    variant_ca_base_impl( variant_ca_base_impl && ) = default;
+
+    // copy assignment
+
+private:
+
+    struct L3
+    {
+        variant_base * this_;
+        variant_base const & r;
+
+        template<class I> void operator()( I i ) const
+        {
+            this_->template emplace<I::value>( r._get_impl( i ) );
+        }
+    };
+
+public:
+
+    BOOST_CXX14_CONSTEXPR variant_ca_base_impl& operator=( variant_ca_base_impl const & r )
+        noexcept( mp11::mp_all<std::is_nothrow_copy_constructible<T>...>::value )
+    {
+        mp11::mp_with_index<sizeof...(T)>( r.index(), L3{ this, r } );
+        return *this;
+    }
+
+    // move assignment
+
+    variant_ca_base_impl& operator=( variant_ca_base_impl && ) = default;
+};
+
+// variant_mc_base
+
+template<bool MoveConstructible, bool TriviallyMoveConstructible, class... T> struct variant_mc_base_impl;
+
+template<class... T> using variant_mc_base = variant_mc_base_impl<
+    mp11::mp_all<std::is_move_constructible<T>...>::value,
+    mp11::mp_all<detail::is_trivially_move_constructible<T>...>::value,
+    T...>;
+
+template<class... T> struct variant_mc_base_impl<true, true, T...>: public variant_ca_base<T...>
+{
+    using variant_base = detail::variant_ca_base<T...>;
+    using variant_base::variant_base;
+
+    variant_mc_base_impl() = default;
+    variant_mc_base_impl( variant_mc_base_impl const& ) = default;
+    variant_mc_base_impl( variant_mc_base_impl && ) = default;
+    variant_mc_base_impl& operator=( variant_mc_base_impl const& ) = default;
+    variant_mc_base_impl& operator=( variant_mc_base_impl && ) = default;
+};
+
+template<bool B, class... T> struct variant_mc_base_impl<false, B, T...>: public variant_ca_base<T...>
+{
+    using variant_base = detail::variant_ca_base<T...>;
+    using variant_base::variant_base;
+
+    variant_mc_base_impl() = default;
+    variant_mc_base_impl( variant_mc_base_impl const& ) = default;
+    variant_mc_base_impl( variant_mc_base_impl && ) = delete;
+    variant_mc_base_impl& operator=( variant_mc_base_impl const& ) = default;
+    variant_mc_base_impl& operator=( variant_mc_base_impl && ) = default;
+};
+
+template<class... T> struct variant_mc_base_impl<true, false, T...>: public variant_ca_base<T...>
+{
+    using variant_base = detail::variant_ca_base<T...>;
+    using variant_base::variant_base;
+
+public:
+
+    // constructors
+
+    variant_mc_base_impl() = default;
+    variant_mc_base_impl( variant_mc_base_impl const& ) = default;
+
+    // move constructor
+
+private:
+
+    struct L2
+    {
+        variant_base * this_;
+        variant_base & r;
+
+        template<class I> void operator()( I i ) const
+        {
+            this_->_replace( i, std::move( r._get_impl( i ) ) );
+        }
+    };
+
+public:
+
+    variant_mc_base_impl( variant_mc_base_impl && r )
+        noexcept( mp11::mp_all<std::is_nothrow_move_constructible<T>...>::value )
+    {
+        mp11::mp_with_index<sizeof...(T)>( r.index(), L2{ this, r } );
+    }
+
+    // assignment
+
+    variant_mc_base_impl& operator=( variant_mc_base_impl const & ) = default;
+    variant_mc_base_impl& operator=( variant_mc_base_impl && ) = default;
+};
+
+// variant_ma_base
+
+template<bool MoveAssignable, bool TriviallyMoveAssignable, class... T> struct variant_ma_base_impl;
+
+template<class... T> using variant_ma_base = variant_ma_base_impl<
+    mp11::mp_all<std::is_move_constructible<T>..., std::is_move_assignable<T>...>::value,
+    mp11::mp_all<detail::is_trivially_destructible<T>..., detail::is_trivially_move_constructible<T>..., detail::is_trivially_move_assignable<T>...>::value,
+    T...>;
+
+template<class... T> struct variant_ma_base_impl<true, true, T...>: public variant_mc_base<T...>
+{
+    using variant_base = detail::variant_mc_base<T...>;
+    using variant_base::variant_base;
+
+    variant_ma_base_impl() = default;
+    variant_ma_base_impl( variant_ma_base_impl const& ) = default;
+    variant_ma_base_impl( variant_ma_base_impl && ) = default;
+    variant_ma_base_impl& operator=( variant_ma_base_impl const& ) = default;
+    variant_ma_base_impl& operator=( variant_ma_base_impl && ) = default;
+};
+
+template<bool B, class... T> struct variant_ma_base_impl<false, B, T...>: public variant_mc_base<T...>
+{
+    using variant_base = detail::variant_mc_base<T...>;
+    using variant_base::variant_base;
+
+    variant_ma_base_impl() = default;
+    variant_ma_base_impl( variant_ma_base_impl const& ) = default;
+    variant_ma_base_impl( variant_ma_base_impl && ) = default;
+    variant_ma_base_impl& operator=( variant_ma_base_impl const& ) = default;
+    variant_ma_base_impl& operator=( variant_ma_base_impl && ) = delete;
+};
+
+template<class... T> struct variant_ma_base_impl<true, false, T...>: public variant_mc_base<T...>
+{
+    using variant_base = detail::variant_mc_base<T...>;
+    using variant_base::variant_base;
+
+public:
+
+    // constructors
+
+    variant_ma_base_impl() = default;
+    variant_ma_base_impl( variant_ma_base_impl const& ) = default;
+    variant_ma_base_impl( variant_ma_base_impl && ) = default;
+
+    // copy assignment
+
+    variant_ma_base_impl& operator=( variant_ma_base_impl const & ) = default;
+
+    // move assignment
+
+private:
+
+    struct L4
+    {
+        variant_base * this_;
+        variant_base & r;
+
+        template<class I> void operator()( I i ) const
+        {
+            this_->template emplace<I::value>( std::move( r._get_impl( i ) ) );
+        }
+    };
+
+public:
+
+    variant_ma_base_impl& operator=( variant_ma_base_impl && r )
+        noexcept( mp11::mp_all<std::is_nothrow_move_constructible<T>...>::value )
+    {
+        mp11::mp_with_index<sizeof...(T)>( r.index(), L4{ this, r } );
+        return *this;
+    }
+};
+
 } // namespace detail
 
 // variant
 
-template<class... T> class variant: private detail::variant_base<T...>
+template<class... T> class variant: private detail::variant_ma_base<T...>
 {
 private:
 
-    using variant_base = detail::variant_base<T...>;
-
-private:
-
-    variant( variant const volatile& r ) = delete;
-    variant& operator=( variant const volatile& r ) = delete;
+    using variant_base = detail::variant_ma_base<T...>;
 
 public:
 
@@ -1076,71 +1568,8 @@ public:
     {
     }
 
-    template<class E1 = void,
-        class E2 = mp11::mp_if<mp11::mp_all<detail::is_trivially_copy_constructible<T>...>, E1>
-    >
-    constexpr variant( variant const& r ) noexcept
-        : variant_base( static_cast<variant_base const&>(r) )
-    {
-    }
-
-private:
-
-    struct L1
-    {
-        variant_base * this_;
-        variant const & r;
-
-        template<class I> void operator()( I i ) const
-        {
-            this_->_replace( i, r._get_impl( i ) );
-        }
-    };
-
-public:
-
-    template<class E1 = void,
-        class E2 = mp11::mp_if<mp11::mp_not<mp11::mp_all<detail::is_trivially_copy_constructible<T>...>>, E1>,
-        class E3 = mp11::mp_if<mp11::mp_all<std::is_copy_constructible<T>...>, E1>
-    >
-    variant( variant const& r )
-        noexcept( mp11::mp_all<std::is_nothrow_copy_constructible<T>...>::value )
-    {
-        mp11::mp_with_index<sizeof...(T)>( r.index(), L1{ this, r } );
-    }
-
-    template<class E1 = void,
-        class E2 = mp11::mp_if<mp11::mp_all<detail::is_trivially_move_constructible<T>...>, E1>
-    >
-    constexpr variant( variant && r ) noexcept
-        : variant_base( static_cast<variant_base&&>(r) )
-    {
-    }
-
-private:
-
-    struct L2
-    {
-        variant_base * this_;
-        variant & r;
-
-        template<class I> void operator()( I i ) const
-        {
-            this_->_replace( i, std::move( r._get_impl( i ) ) );
-        }
-    };
-
-public:
-
-    template<class E1 = void,
-        class E2 = mp11::mp_if<mp11::mp_not<mp11::mp_all<detail::is_trivially_move_constructible<T>...>>, E1>,
-        class E3 = mp11::mp_if<mp11::mp_all<std::is_move_constructible<T>...>, E1>
-    >
-    variant( variant && r )
-        noexcept( mp11::mp_all<std::is_nothrow_move_constructible<T>...>::value )
-    {
-        mp11::mp_with_index<sizeof...(T)>( r.index(), L2{ this, r } );
-    }
+    // variant( variant const& ) = default;
+    // variant( variant && ) = default;
 
     template<class U,
         class Ud = typename std::decay<U>::type,
@@ -1175,75 +1604,9 @@ public:
     }
 
     // assignment
-    template<class E1 = void,
-        class E2 = mp11::mp_if<mp11::mp_all<std::is_trivially_destructible<T>..., detail::is_trivially_copy_constructible<T>..., detail::is_trivially_copy_assignable<T>...>, E1>
-    >
-    BOOST_CXX14_CONSTEXPR variant& operator=( variant const & r ) noexcept
-    {
-        static_cast<variant_base&>( *this ) = static_cast<variant_base const&>( r );
-        return *this;
-    }
 
-private:
-
-    struct L3
-    {
-        variant * this_;
-        variant const & r;
-
-        template<class I> void operator()( I i ) const
-        {
-            this_->variant_base::template emplace<I::value>( r._get_impl( i ) );
-        }
-    };
-
-public:
-
-    template<class E1 = void,
-        class E2 = mp11::mp_if<mp11::mp_not<mp11::mp_all<std::is_trivially_destructible<T>..., detail::is_trivially_copy_constructible<T>..., detail::is_trivially_copy_assignable<T>...>>, E1>,
-        class E3 = mp11::mp_if<mp11::mp_all<std::is_copy_constructible<T>..., std::is_copy_assignable<T>...>, E1>
-    >
-    BOOST_CXX14_CONSTEXPR variant& operator=( variant const & r )
-        noexcept( mp11::mp_all<std::is_nothrow_copy_constructible<T>...>::value )
-    {
-        mp11::mp_with_index<sizeof...(T)>( r.index(), L3{ this, r } );
-        return *this;
-    }
-
-    template<class E1 = void,
-        class E2 = mp11::mp_if<mp11::mp_all<std::is_trivially_destructible<T>..., detail::is_trivially_move_constructible<T>..., detail::is_trivially_move_assignable<T>...>, E1>
-    >
-    BOOST_CXX14_CONSTEXPR variant& operator=( variant && r ) noexcept
-    {
-        static_cast<variant_base&>( *this ) = static_cast<variant_base&&>( r );
-        return *this;
-    }
-
-private:
-
-    struct L4
-    {
-        variant * this_;
-        variant & r;
-
-        template<class I> void operator()( I i ) const
-        {
-            this_->variant_base::template emplace<I::value>( std::move( r._get_impl( i ) ) );
-        }
-    };
-
-public:
-
-    template<class E1 = void,
-        class E2 = mp11::mp_if<mp11::mp_not<mp11::mp_all<std::is_trivially_destructible<T>..., detail::is_trivially_move_constructible<T>..., detail::is_trivially_move_assignable<T>...>>, E1>,
-        class E3 = mp11::mp_if<mp11::mp_all<std::is_move_constructible<T>..., std::is_move_assignable<T>...>, E1>
-    >
-    variant& operator=( variant && r )
-        noexcept( mp11::mp_all<std::is_nothrow_move_constructible<T>...>::value )
-    {
-        mp11::mp_with_index<sizeof...(T)>( r.index(), L4{ this, r } );
-        return *this;
-    }
+    // variant& operator=( variant const& ) = default;
+    // variant& operator=( variant && ) = default;
 
     template<class U,
         class E1 = typename std::enable_if<!std::is_same<typename std::decay<U>::type, variant>::value>::type,
@@ -1598,6 +1961,25 @@ namespace detail
 
 template<class T> using remove_cv_ref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
 
+template<class... T> variant<T...> const & extract_variant_base_( variant<T...> const & );
+
+#if BOOST_WORKAROUND( BOOST_MSVC, < 1930 )
+
+template<class V> struct extract_vbase_impl
+{
+    using type = decltype( extract_variant_base_( std::declval<V>() ) );
+};
+
+template<class V> using extract_variant_base = remove_cv_ref_t< typename extract_vbase_impl<V>::type >;
+
+#else
+
+template<class V> using extract_variant_base = remove_cv_ref_t< decltype( extract_variant_base_( std::declval<V>() ) ) >;
+
+#endif
+
+template<class V> using variant_base_size = variant_size< extract_variant_base<V> >;
+
 template<class T, class U> struct copy_cv_ref
 {
     using type = T;
@@ -1637,13 +2019,28 @@ template<class F> struct Qret
 
 template<class L> using front_if_same = mp11::mp_if<mp11::mp_apply<mp11::mp_same, L>, mp11::mp_front<L>>;
 
-template<class V> using apply_cv_ref = mp11::mp_product<copy_cv_ref_t, remove_cv_ref_t<V>, mp11::mp_list<V>>;
+template<class V> using apply_cv_ref = mp11::mp_product<copy_cv_ref_t, extract_variant_base<V>, mp11::mp_list<V>>;
 
-template<class F, class... V> using Vret = front_if_same<mp11::mp_product_q<Qret<F>, apply_cv_ref<V>...>>;
+struct deduced {};
+
+#if !BOOST_WORKAROUND( BOOST_MSVC, < 1920 )
+
+template<class R, class F, class... V> using Vret = mp11::mp_eval_if_not< std::is_same<R, deduced>, R, front_if_same, mp11::mp_product_q<Qret<F>, apply_cv_ref<V>...> >;
+
+#else
+
+template<class R, class F, class... V> struct Vret_impl
+{
+    using type = mp11::mp_eval_if_not< std::is_same<R, deduced>, R, front_if_same, mp11::mp_product_q<Qret<F>, apply_cv_ref<V>...> >;
+};
+
+template<class R, class F, class... V> using Vret = typename Vret_impl<R, F, V...>::type;
+
+#endif
 
 } // namespace detail
 
-template<class F> constexpr auto visit( F&& f ) -> decltype(std::forward<F>(f)())
+template<class R = detail::deduced, class F> constexpr auto visit( F&& f ) -> detail::Vret<R, F>
 {
     return std::forward<F>(f)();
 }
@@ -1651,12 +2048,12 @@ template<class F> constexpr auto visit( F&& f ) -> decltype(std::forward<F>(f)()
 namespace detail
 {
 
-template<class F, class V1> struct visit_L1
+template<class R, class F, class V1> struct visit_L1
 {
     F&& f;
     V1&& v1;
 
-    template<class I> auto operator()( I ) const -> Vret<F, V1>
+    template<class I> auto operator()( I ) const -> Vret<R, F, V1>
     {
         return std::forward<F>(f)( unsafe_get<I::value>( std::forward<V1>(v1) ) );
     }
@@ -1664,9 +2061,9 @@ template<class F, class V1> struct visit_L1
 
 } // namespace detail
 
-template<class F, class V1> constexpr auto visit( F&& f, V1&& v1 ) -> detail::Vret<F, V1>
+template<class R = detail::deduced, class F, class V1> constexpr auto visit( F&& f, V1&& v1 ) -> detail::Vret<R, F, V1>
 {
-    return mp11::mp_with_index<variant_size<V1>>( v1.index(), detail::visit_L1<F, V1>{ std::forward<F>(f), std::forward<V1>(v1) } );
+    return mp11::mp_with_index<detail::variant_base_size<V1>>( v1.index(), detail::visit_L1<R, F, V1>{ std::forward<F>(f), std::forward<V1>(v1) } );
 }
 
 #if defined(BOOST_NO_CXX14_GENERIC_LAMBDAS) || BOOST_WORKAROUND( BOOST_MSVC, < 1920 )
@@ -1690,31 +2087,31 @@ template<class F, class A> bind_front_<F, A> bind_front( F&& f, A&& a )
     return bind_front_<F, A>{ std::forward<F>(f), std::forward<A>(a) };
 }
 
-template<class F, class V1, class V2> struct visit_L2
+template<class R, class F, class V1, class V2> struct visit_L2
 {
     F&& f;
 
     V1&& v1;
     V2&& v2;
 
-    template<class I> auto operator()( I ) const -> Vret<F, V1, V2>
+    template<class I> auto operator()( I ) const -> Vret<R, F, V1, V2>
     {
         auto f2 = bind_front( std::forward<F>(f), unsafe_get<I::value>( std::forward<V1>(v1) ) );
-        return visit( f2, std::forward<V2>(v2) );
+        return visit<R>( f2, std::forward<V2>(v2) );
     }
 };
 
 } // namespace detail
 
-template<class F, class V1, class V2> constexpr auto visit( F&& f, V1&& v1, V2&& v2 ) -> detail::Vret<F, V1, V2>
+template<class R = detail::deduced, class F, class V1, class V2> constexpr auto visit( F&& f, V1&& v1, V2&& v2 ) -> detail::Vret<R, F, V1, V2>
 {
-    return mp11::mp_with_index<variant_size<V1>>( v1.index(), detail::visit_L2<F, V1, V2>{ std::forward<F>(f), std::forward<V1>(v1), std::forward<V2>(v2) } );
+    return mp11::mp_with_index<detail::variant_base_size<V1>>( v1.index(), detail::visit_L2<R, F, V1, V2>{ std::forward<F>(f), std::forward<V1>(v1), std::forward<V2>(v2) } );
 }
 
 namespace detail
 {
 
-template<class F, class V1, class V2, class V3> struct visit_L3
+template<class R, class F, class V1, class V2, class V3> struct visit_L3
 {
     F&& f;
 
@@ -1722,24 +2119,24 @@ template<class F, class V1, class V2, class V3> struct visit_L3
     V2&& v2;
     V3&& v3;
 
-    template<class I> auto operator()( I ) const -> Vret<F, V1, V2, V3>
+    template<class I> auto operator()( I ) const -> Vret<R, F, V1, V2, V3>
     {
         auto f2 = bind_front( std::forward<F>(f), unsafe_get<I::value>( std::forward<V1>(v1) ) );
-        return visit( f2, std::forward<V2>(v2), std::forward<V3>(v3) );
+        return visit<R>( f2, std::forward<V2>(v2), std::forward<V3>(v3) );
     }
 };
 
 } // namespace detail
 
-template<class F, class V1, class V2, class V3> constexpr auto visit( F&& f, V1&& v1, V2&& v2, V3&& v3 ) -> detail::Vret<F, V1, V2, V3>
+template<class R = detail::deduced, class F, class V1, class V2, class V3> constexpr auto visit( F&& f, V1&& v1, V2&& v2, V3&& v3 ) -> detail::Vret<R, F, V1, V2, V3>
 {
-    return mp11::mp_with_index<variant_size<V1>>( v1.index(), detail::visit_L3<F, V1, V2, V3>{ std::forward<F>(f), std::forward<V1>(v1), std::forward<V2>(v2), std::forward<V3>(v3) } );
+    return mp11::mp_with_index<detail::variant_base_size<V1>>( v1.index(), detail::visit_L3<R, F, V1, V2, V3>{ std::forward<F>(f), std::forward<V1>(v1), std::forward<V2>(v2), std::forward<V3>(v3) } );
 }
 
 namespace detail
 {
 
-template<class F, class V1, class V2, class V3, class V4> struct visit_L4
+template<class R, class F, class V1, class V2, class V3, class V4> struct visit_L4
 {
     F&& f;
 
@@ -1748,28 +2145,28 @@ template<class F, class V1, class V2, class V3, class V4> struct visit_L4
     V3&& v3;
     V4&& v4;
 
-    template<class I> auto operator()( I ) const -> Vret<F, V1, V2, V3, V4>
+    template<class I> auto operator()( I ) const -> Vret<R, F, V1, V2, V3, V4>
     {
         auto f2 = bind_front( std::forward<F>(f), unsafe_get<I::value>( std::forward<V1>(v1) ) );
-        return visit( f2, std::forward<V2>(v2), std::forward<V3>(v3), std::forward<V4>(v4) );
+        return visit<R>( f2, std::forward<V2>(v2), std::forward<V3>(v3), std::forward<V4>(v4) );
     }
 };
 
 } // namespace detail
 
-template<class F, class V1, class V2, class V3, class V4> constexpr auto visit( F&& f, V1&& v1, V2&& v2, V3&& v3, V4&& v4 ) -> detail::Vret<F, V1, V2, V3, V4>
+template<class R = detail::deduced, class F, class V1, class V2, class V3, class V4> constexpr auto visit( F&& f, V1&& v1, V2&& v2, V3&& v3, V4&& v4 ) -> detail::Vret<R, F, V1, V2, V3, V4>
 {
-    return mp11::mp_with_index<variant_size<V1>>( v1.index(), detail::visit_L4<F, V1, V2, V3, V4>{ std::forward<F>(f), std::forward<V1>(v1), std::forward<V2>(v2), std::forward<V3>(v3), std::forward<V4>(v4) } );
+    return mp11::mp_with_index<detail::variant_base_size<V1>>( v1.index(), detail::visit_L4<R, F, V1, V2, V3, V4>{ std::forward<F>(f), std::forward<V1>(v1), std::forward<V2>(v2), std::forward<V3>(v3), std::forward<V4>(v4) } );
 }
 
 #else
 
-template<class F, class V1, class V2, class... V> constexpr auto visit( F&& f, V1&& v1, V2&& v2, V&&... v ) -> detail::Vret<F, V1, V2, V...>
+template<class R = detail::deduced, class F, class V1, class V2, class... V> constexpr auto visit( F&& f, V1&& v1, V2&& v2, V&&... v ) -> detail::Vret<R, F, V1, V2, V...>
 {
-    return mp11::mp_with_index<variant_size<V1>>( v1.index(), [&]( auto I ){
+    return mp11::mp_with_index<detail::variant_base_size<V1>>( v1.index(), [&]( auto I ){
 
         auto f2 = [&]( auto&&... a ){ return std::forward<F>(f)( detail::unsafe_get<I.value>( std::forward<V1>(v1) ), std::forward<decltype(a)>(a)... ); };
-        return visit( f2, std::forward<V2>(v2), std::forward<V>(v)... );
+        return visit<R>( f2, std::forward<V2>(v2), std::forward<V>(v)... );
 
     });
 }
@@ -1785,9 +2182,92 @@ void swap( variant<T...> & v, variant<T...> & w )
     v.swap( w );
 }
 
+// hashing support
+
+namespace detail
+{
+
+template<class V> struct hash_value_L
+{
+    V const & v;
+
+    template<class I> std::size_t operator()( I ) const
+    {
+        boost::ulong_long_type hv = ( boost::ulong_long_type( 0xCBF29CE4 ) << 32 ) + 0x84222325;
+        boost::ulong_long_type const prime = ( boost::ulong_long_type( 0x00000100 ) << 32 ) + 0x000001B3;
+
+        // index
+
+        hv ^= I::value;
+        hv *= prime;
+
+        // value
+
+        auto const & t = unsafe_get<I::value>( v );
+
+        hv ^= std::hash<remove_cv_ref_t<decltype(t)>>()( t );
+        hv *= prime;
+
+        return static_cast<std::size_t>( hv );
+    }
+};
+
+} // namespace detail
+
+inline std::size_t hash_value( monostate const & )
+{
+    return 0xA7EE4757u;
+}
+
+template<class... T> std::size_t hash_value( variant<T...> const & v )
+{
+    return mp11::mp_with_index<sizeof...(T)>( v.index(), detail::hash_value_L< variant<T...> >{ v } );
+}
+
+namespace detail
+{
+
+template<class T> using is_hash_enabled = std::is_default_constructible< std::hash<typename std::remove_const<T>::type> >;
+
+template<class V, bool E = mp11::mp_all_of<V, is_hash_enabled>::value> struct std_hash_impl;
+
+template<class V> struct std_hash_impl<V, false>
+{
+    std_hash_impl() = delete;
+    std_hash_impl( std_hash_impl const& ) = delete;
+    std_hash_impl& operator=( std_hash_impl const& ) = delete;
+};
+
+template<class V> struct std_hash_impl<V, true>
+{
+    std::size_t operator()( V const & v ) const
+    {
+        return hash_value( v );
+    }
+};
+
+} // namespace detail
+
 } // namespace variant2
 } // namespace boost
 
+namespace std
+{
+
+template<class... T> struct hash< ::boost::variant2::variant<T...> >: public ::boost::variant2::detail::std_hash_impl< ::boost::variant2::variant<T...> >
+{
+};
+
+template<> struct hash< ::boost::variant2::monostate >
+{
+    std::size_t operator()( ::boost::variant2::monostate const & v ) const
+    {
+        return hash_value( v );
+    }
+};
+
+} // namespace std
+
 #if defined(_MSC_VER) && _MSC_VER < 1910
 # pragma warning( pop )
 #endif

meta/libraries.json

@@ -5,10 +5,11 @@
         "Peter Dimov"
     ],
     "maintainers": [
-        "Peter Dimov <pdimov -at- pdimov.com>"
+        "Peter Dimov <pdimov -at- gmail.com>"
     ],
     "description": "A never-valueless, strong guarantee implementation of std::variant.",
     "category": [
         "Containers", "Data"
-    ]
+    ],
+    "cxxstd": "11"
 }

test/CMakeLists.txt

@@ -6,6 +6,6 @@ include(BoostTestJamfile OPTIONAL RESULT_VARIABLE HAVE_BOOST_TEST)
 
 if(HAVE_BOOST_TEST)
 
-boost_test_jamfile(FILE Jamfile LINK_LIBRARIES Boost::variant2 Boost::core)
+boost_test_jamfile(FILE Jamfile LINK_LIBRARIES Boost::variant2 Boost::core Boost::container_hash)
 
 endif()

test/Jamfile

@@ -12,7 +12,7 @@ import ../../config/checks/config : requires ;
 project
   : default-build
 
-    <warnings>all
+    <warnings>extra
 
   : requirements
 
@@ -29,16 +29,16 @@ run variant_size.cpp ;
 run variant_alternative.cpp ;
 
 run variant_holds_alternative.cpp ;
-compile variant_holds_alternative_cx.cpp ;
+compile variant_holds_alternative_cx.cpp : <toolset>msvc-14.0:<build>no ;
 
 run variant_get_by_index.cpp ;
-compile variant_get_by_index_cx.cpp ;
+compile variant_get_by_index_cx.cpp : <toolset>msvc-14.0:<build>no ;
 
 run variant_get_by_type.cpp ;
-compile variant_get_by_type_cx.cpp ;
+compile variant_get_by_type_cx.cpp : <toolset>msvc-14.0:<build>no ;
 
 run variant_default_construct.cpp ;
-compile variant_default_construct_cx.cpp ;
+compile variant_default_construct_cx.cpp : <toolset>msvc-14.0:<build>no ;
 
 run variant_copy_construct.cpp ;
 compile variant_copy_construct_cx.cpp : <toolset>msvc-14.0:<build>no ;
@@ -47,13 +47,13 @@ run variant_move_construct.cpp ;
 compile variant_move_construct_cx.cpp : [ requires cxx14_constexpr ] ;
 
 run variant_value_construct.cpp ;
-compile variant_value_construct_cx.cpp ;
+compile variant_value_construct_cx.cpp : <toolset>msvc-14.0:<build>no ;
 
 run variant_in_place_index_construct.cpp ;
-compile variant_in_place_index_construct_cx.cpp ;
+compile variant_in_place_index_construct_cx.cpp : <toolset>msvc-14.0:<build>no ;
 
 run variant_in_place_type_construct.cpp ;
-compile variant_in_place_type_construct_cx.cpp ;
+compile variant_in_place_type_construct_cx.cpp : <toolset>msvc-14.0:<build>no ;
 
 run variant_copy_assign.cpp ;
 compile variant_copy_assign_cx.cpp : [ requires cxx14_constexpr ] ;
@@ -99,9 +99,23 @@ local NX =
     ;
 
 run variant_get_by_index.cpp throw_exception.cpp : : : $(NX) : variant_get_by_index_nx ;
-compile variant_get_by_index_cx.cpp : $(NX) : variant_get_by_index_cx_nx ;
+compile variant_get_by_index_cx.cpp : $(NX) <toolset>msvc-14.0:<build>no : variant_get_by_index_cx_nx ;
 
 run variant_get_by_type.cpp throw_exception.cpp : : : $(NX) : variant_get_by_type_nx ;
-compile variant_get_by_type_cx.cpp : $(NX) : variant_get_by_type_cx_nx ;
+compile variant_get_by_type_cx.cpp : $(NX) <toolset>msvc-14.0:<build>no : variant_get_by_type_cx_nx ;
 
 run variant_subset.cpp throw_exception.cpp : : : $(NX) : variant_subset_nx ;
+
+run variant_hash.cpp ;
+
+run variant_trivial.cpp ;
+run variant_special.cpp ;
+
+run variant_visit_derived.cpp ;
+
+run variant_many_types.cpp ;
+
+run variant_visit_r.cpp : : :
+    <toolset>gcc,<target-os>windows:<variant>release
+    <toolset>gcc,<target-os>cygwin:<variant>release
+    ;

test/variant_copy_construct.cpp

@@ -9,6 +9,8 @@
 #include <boost/variant2/variant.hpp>
 #include <boost/core/lightweight_test.hpp>
 #include <boost/core/lightweight_test_trait.hpp>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
 #include <type_traits>
 #include <utility>
 #include <string>
@@ -48,12 +50,21 @@ struct Y
     Y( Y const& ) = delete;
 };
 
+struct D
+{
+    ~D() {}
+};
+
+inline bool operator==( D, D ) { return true; }
+
 template<class V> static void test( V const & v )
 {
     V v2( v );
 
     BOOST_TEST_EQ( v.index(), v2.index() );
     BOOST_TEST( v == v2 );
+
+    BOOST_TEST_TRAIT_TRUE((std::is_copy_constructible<V>));
 }
 
 int main()
@@ -115,6 +126,12 @@ int main()
         test( v );
     }
 
+#if !BOOST_WORKAROUND( __GNUC__, < 5 )
+
+    test( variant<D>() );
+
+#endif
+
     {
         BOOST_TEST_TRAIT_TRUE((std::is_nothrow_copy_constructible<variant<int>>));
         BOOST_TEST_TRAIT_TRUE((std::is_nothrow_copy_constructible<variant<int const>>));

test/variant_emplace_index.cpp

@@ -57,6 +57,60 @@ STATIC_ASSERT( !std::is_nothrow_move_constructible<X2>::value );
 STATIC_ASSERT( !std::is_nothrow_copy_assignable<X2>::value );
 STATIC_ASSERT( !std::is_nothrow_move_assignable<X2>::value );
 
+struct Y1
+{
+    int v = 1;
+
+    Y1() = default;
+    Y1(Y1 const&) = delete;
+    Y1(Y1&&) = delete;
+};
+
+STATIC_ASSERT( !std::is_copy_constructible<Y1>::value );
+STATIC_ASSERT( !std::is_move_constructible<Y1>::value );
+
+struct Y2
+{
+    int v = 2;
+
+    Y2() = default;
+    Y2(Y2 const&) = delete;
+    Y2(Y2&&) = delete;
+};
+
+STATIC_ASSERT( !std::is_copy_constructible<Y2>::value );
+STATIC_ASSERT( !std::is_move_constructible<Y2>::value );
+
+struct Z1
+{
+    static int instances;
+
+    int v = 1;
+
+    Z1() { ++instances; }
+    ~Z1() { --instances; }
+
+    Z1(Z1 const&) = delete;
+    Z1(Z1&&) = delete;
+};
+
+int Z1::instances = 0;
+
+struct Z2
+{
+    static int instances;
+
+    int v = 2;
+
+    Z2() { ++instances; }
+    ~Z2() { --instances; }
+
+    Z2(Z2 const&) = delete;
+    Z2(Z2&&) = delete;
+};
+
+int Z2::instances = 0;
+
 int main()
 {
     {
@@ -177,5 +231,62 @@ int main()
         BOOST_TEST_EQ( get<0>(v).v, 4 );
     }
 
+    {
+        variant<Y1, Y2> v;
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+    }
+
+    {
+        variant<Z1, Z2> v;
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+        BOOST_TEST_EQ( Z1::instances, 1 );
+        BOOST_TEST_EQ( Z2::instances, 0 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+        BOOST_TEST_EQ( Z1::instances, 1 );
+        BOOST_TEST_EQ( Z2::instances, 0 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+        BOOST_TEST_EQ( Z1::instances, 0 );
+        BOOST_TEST_EQ( Z2::instances, 1 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+        BOOST_TEST_EQ( Z1::instances, 0 );
+        BOOST_TEST_EQ( Z2::instances, 1 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+        BOOST_TEST_EQ( Z1::instances, 1 );
+        BOOST_TEST_EQ( Z2::instances, 0 );
+    }
+
+    BOOST_TEST_EQ( Z1::instances, 0 );
+    BOOST_TEST_EQ( Z2::instances, 0 );
+
     return boost::report_errors();
 }

test/variant_get_by_index.cpp

@@ -6,6 +6,12 @@
 // See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt
 
+#if defined( __clang__ ) && defined( __has_warning )
+# if __has_warning( "-Wdeprecated-volatile" )
+#  pragma clang diagnostic ignored "-Wdeprecated-volatile"
+# endif
+#endif
+
 #include <boost/variant2/variant.hpp>
 #include <boost/core/lightweight_test.hpp>
 #include <boost/core/lightweight_test_trait.hpp>

test/variant_get_by_type.cpp

@@ -6,6 +6,12 @@
 // See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt
 
+#if defined( __clang__ ) && defined( __has_warning )
+# if __has_warning( "-Wdeprecated-volatile" )
+#  pragma clang diagnostic ignored "-Wdeprecated-volatile"
+# endif
+#endif
+
 #include <boost/variant2/variant.hpp>
 #include <boost/core/lightweight_test.hpp>
 #include <boost/core/lightweight_test_trait.hpp>

test/variant_hash.cpp

@@ -0,0 +1,73 @@
+
+// Copyright 2020 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#if defined(_MSC_VER)
+# pragma warning( disable: 4244 ) // conversion from int to float, possible loss of data
+#endif
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/container_hash/hash.hpp>
+#include <boost/config/workaround.hpp>
+
+using namespace boost::variant2;
+
+template<template<class...> class Hash, class T1, class T2, class T3> void test()
+{
+    variant<T1, T2, T3> v1( in_place_index_t<0>{} );
+    std::size_t h1 = Hash<decltype(v1)>()( v1 );
+
+    variant<T1, T2, T3> v2( in_place_index_t<1>{} );
+    std::size_t h2 = Hash<decltype(v2)>()( v2 );
+
+    variant<T1, T2, T3> v3( in_place_index_t<2>{} );
+    std::size_t h3 = Hash<decltype(v3)>()( v3 );
+
+    BOOST_TEST_NE( h1, h2 );
+    BOOST_TEST_NE( h1, h3 );
+    BOOST_TEST_NE( h2, h3 );
+}
+
+template<template<class...> class Hash, class T> void test2()
+{
+    variant<T> v1( 0 );
+    std::size_t h1 = Hash<decltype(v1)>()( v1 );
+
+    variant<T> v2( 1 );
+    std::size_t h2 = Hash<decltype(v2)>()( v2 );
+
+    variant<T> v3( 2 );
+    std::size_t h3 = Hash<decltype(v3)>()( v3 );
+
+    BOOST_TEST_NE( h1, h2 );
+    BOOST_TEST_NE( h1, h3 );
+    BOOST_TEST_NE( h2, h3 );
+}
+
+struct X {};
+
+int main()
+{
+    test<std::hash, monostate, monostate, monostate>();
+    test<std::hash, int, int, float>();
+
+    test<boost::hash, monostate, monostate, monostate>();
+    test<boost::hash, int, int, float>();
+
+    test2<std::hash, int>();
+    test2<std::hash, float>();
+
+    test2<boost::hash, int>();
+    test2<boost::hash, float>();
+
+#if !BOOST_WORKAROUND(BOOST_MSVC, < 1910) && ( !defined(_LIBCPP_STD_VER) || _LIBCPP_STD_VER > 11 )
+
+    BOOST_TEST_TRAIT_FALSE(( detail::is_hash_enabled<X> ));
+
+#endif
+
+    return boost::report_errors();
+}

test/variant_in_place_index_construct_cx.cpp

@@ -7,11 +7,8 @@
 // http://www.boost.org/LICENSE_1_0.txt
 
 #include <boost/variant2/variant.hpp>
-#include <boost/core/lightweight_test.hpp>
-#include <boost/core/lightweight_test_trait.hpp>
-#include <type_traits>
-#include <utility>
-#include <string>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
 
 using namespace boost::variant2;
 
@@ -108,9 +105,17 @@ int main()
         STATIC_ASSERT( v.index() == 4 );
     }
 
+#if BOOST_WORKAROUND(BOOST_GCC, >= 100000 && BOOST_GCC < 100200)
+
+    // no idea why this fails on g++ 10
+
+#else
+
     {
         constexpr variant<int, int, float, float, X, X> v( in_place_index_t<5>{}, 0, 0 );
 
         STATIC_ASSERT( v.index() == 5 );
     }
+
+#endif
 }

test/variant_in_place_type_construct_cx.cpp

@@ -7,6 +7,8 @@
 // http://www.boost.org/LICENSE_1_0.txt
 
 #include <boost/variant2/variant.hpp>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
 
 using namespace boost::variant2;
 
@@ -100,6 +102,12 @@ int main()
         STATIC_ASSERT( holds_alternative<X>(v) );
     }
 
+#if BOOST_WORKAROUND(BOOST_GCC, >= 100000 && BOOST_GCC < 100200)
+
+    // no idea why this fails on g++ 10
+
+#else
+
     {
         constexpr variant<int, int, float, float, X> v( in_place_type_t<X>{}, 0, 0 );
 
@@ -107,4 +115,6 @@ int main()
 
         STATIC_ASSERT( holds_alternative<X>(v) );
     }
+
+#endif
 }

test/variant_many_types.cpp

@@ -0,0 +1,109 @@
+
+// Copyright 2020 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if defined(_MSC_VER)
+# pragma warning( disable: 4503 ) // decorated name length exceeded
+#endif
+
+#include <boost/variant2/variant.hpp>
+#include <boost/mp11.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+using namespace boost::mp11;
+
+template<class I> struct X
+{
+    static int const value = I::value;
+    int v_;
+};
+
+template<class I> int const X<I>::value;
+
+template<class I> struct Y
+{
+    static int const value = I::value;
+    int v_;
+
+    Y() = default;
+    Y( Y const& ) = default;
+
+    explicit Y( int v ): v_( v ) {}
+
+    Y& operator=( Y const& ) noexcept = default;
+
+    Y& operator=( Y&& r ) noexcept
+    {
+        v_ = r.v_;
+        return *this;
+    }
+};
+
+template<class I> int const Y<I>::value;
+
+template<class I> struct Z
+{
+    static int const value = I::value;
+    int v_;
+
+    ~Z() {}
+};
+
+template<class I> int const Z<I>::value;
+
+template<class V> struct F1
+{
+    template<class T> void operator()( T ) const
+    {
+        int const i = T::value;
+
+        T t{ i * 2 };
+
+        using boost::variant2::get;
+
+        {
+            V v( t );
+
+            BOOST_TEST_EQ( v.index(), i );
+            BOOST_TEST_EQ( get<i>( v ).v_, t.v_ );
+            BOOST_TEST_EQ( get<T>( v ).v_, t.v_ );
+        }
+
+        {
+            V const v( t );
+
+            BOOST_TEST_EQ( v.index(), i );
+            BOOST_TEST_EQ( get<i>( v ).v_, t.v_ );
+            BOOST_TEST_EQ( get<T>( v ).v_, t.v_ );
+        }
+
+        {
+            V v;
+
+            v = t;
+
+            BOOST_TEST_EQ( v.index(), i );
+            BOOST_TEST_EQ( get<i>( v ).v_, t.v_ );
+            BOOST_TEST_EQ( get<T>( v ).v_, t.v_ );
+        }
+    }
+};
+
+template<class V> void test()
+{
+    mp_for_each<V>( F1<V>() );
+}
+
+int main()
+{
+    int const N = 32;
+
+    using V = mp_rename<mp_iota_c<N>, boost::variant2::variant>;
+
+    test< mp_transform<X, V> >();
+    test< mp_transform<Y, V> >();
+    test< mp_transform<Z, V> >();
+
+    return boost::report_errors();
+}

test/variant_special.cpp

@@ -0,0 +1,103 @@
+// Copyright 2020 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if defined(_MSC_VER) && _MSC_VER < 1910
+# pragma warning(disable: 4503) // decorated name length exceeded
+#endif
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
+
+#include <boost/mp11.hpp>
+using namespace boost::mp11;
+
+//
+
+using namespace boost::variant2;
+
+struct D
+{
+    ~D() noexcept {}
+};
+
+struct CC1
+{
+    CC1( CC1 const& ) {}
+};
+
+struct CC2
+{
+    CC2( CC2 const& ) = delete;
+};
+
+struct MC1
+{
+    MC1( MC1 && ) {}
+};
+
+struct MC2
+{
+    MC2( MC2 && ) = delete;
+};
+
+struct CA1
+{
+    CA1& operator=( CA1 const& ) { return *this; }
+};
+
+struct CA2
+{
+    CA2& operator=( CA2 const& ) = delete;
+};
+
+struct MA1
+{
+    MA1& operator=( MA1 && ) { return *this; }
+};
+
+struct MA2
+{
+    MA2& operator=( MA2 && ) = delete;
+};
+
+struct test
+{
+    template<class... T> void operator()( mp_list<T...> ) const noexcept
+    {
+        using U = mp_inherit<T...>;
+
+#if !BOOST_WORKAROUND( __GNUC__, < 5 )
+
+        BOOST_TEST_EQ( std::is_copy_constructible<variant<U>>::value, std::is_copy_constructible<U>::value );
+        BOOST_TEST_EQ( std::is_nothrow_copy_constructible<variant<U>>::value, std::is_nothrow_copy_constructible<U>::value );
+
+#endif
+
+#if !BOOST_WORKAROUND(BOOST_MSVC, < 1910)
+
+        BOOST_TEST_EQ( std::is_move_constructible<variant<U>>::value, std::is_move_constructible<U>::value );
+
+#else
+
+        BOOST_TEST_GE( std::is_move_constructible<variant<U>>::value, std::is_move_constructible<U>::value );
+
+#endif
+
+        BOOST_TEST_EQ( std::is_nothrow_move_constructible<variant<U>>::value, std::is_nothrow_move_constructible<U>::value );
+
+        BOOST_TEST_EQ( std::is_copy_assignable<variant<U>>::value, std::is_copy_constructible<U>::value && std::is_copy_assignable<U>::value );
+        BOOST_TEST_EQ( std::is_nothrow_copy_assignable<variant<U>>::value, std::is_nothrow_copy_constructible<U>::value && std::is_copy_assignable<U>::value );
+
+        BOOST_TEST_EQ( std::is_move_assignable<variant<U>>::value, std::is_move_constructible<U>::value && std::is_move_assignable<U>::value );
+        BOOST_TEST_EQ( std::is_nothrow_move_assignable<variant<U>>::value, std::is_nothrow_move_constructible<U>::value && std::is_move_assignable<U>::value );
+    }
+};
+
+int main()
+{
+    mp_for_each< mp_power_set< mp_list<D, CC1, CC2, MC1, MC2, CA1, CA2, MA1, MA2> > >( test() );
+    return boost::report_errors();
+}

test/variant_trivial.cpp

@@ -0,0 +1,95 @@
+// Copyright 2020 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if defined(_MSC_VER) && _MSC_VER < 1910
+# pragma warning(disable: 4503) // decorated name length exceeded
+#endif
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
+
+#include <boost/mp11.hpp>
+using namespace boost::mp11;
+
+//
+
+struct D
+{
+    ~D() noexcept {}
+};
+
+struct CC1
+{
+    CC1( CC1 const& ) noexcept {}
+};
+
+struct CC2
+{
+    CC2( CC2 const& ) = delete;
+};
+
+struct MC1
+{
+    MC1( MC1 && ) noexcept {}
+};
+
+struct MC2
+{
+    MC2( MC2 && ) = delete;
+};
+
+struct CA1
+{
+    CA1& operator=( CA1 const& ) noexcept { return *this; }
+};
+
+struct CA2
+{
+    CA2& operator=( CA2 const& ) = delete;
+};
+
+struct MA1
+{
+    MA1& operator=( MA1 && ) noexcept { return *this; }
+};
+
+struct MA2
+{
+    MA2& operator=( MA2 && ) = delete;
+};
+
+using namespace boost::variant2;
+namespace v2d = boost::variant2::detail;
+
+struct test
+{
+    template<class... T> void operator()( mp_list<T...> ) const noexcept
+    {
+        using U = mp_inherit<T...>;
+
+#if !BOOST_WORKAROUND( __GNUC__, < 5 )
+
+        BOOST_TEST_EQ( v2d::is_trivially_copy_constructible<variant<U>>::value, v2d::is_trivially_copy_constructible<U>::value );
+        BOOST_TEST_EQ( v2d::is_trivially_copy_assignable<variant<U>>::value, std::is_trivially_destructible<U>::value && v2d::is_trivially_copy_constructible<U>::value && v2d::is_trivially_copy_assignable<U>::value );
+
+#endif
+
+        BOOST_TEST_EQ( std::is_trivially_destructible<variant<U>>::value, std::is_trivially_destructible<U>::value );
+
+#if !BOOST_WORKAROUND(BOOST_LIBSTDCXX_VERSION, < 50000)
+
+        BOOST_TEST_EQ( v2d::is_trivially_move_constructible<variant<U>>::value, v2d::is_trivially_move_constructible<U>::value );
+        BOOST_TEST_EQ( v2d::is_trivially_move_assignable<variant<U>>::value, std::is_trivially_destructible<U>::value && v2d::is_trivially_move_constructible<U>::value && v2d::is_trivially_move_assignable<U>::value );
+
+#endif
+    }
+};
+
+int main()
+{
+    mp_for_each< mp_power_set< mp_list<D, CC1, CC2, MC1, MC2, CA1, CA2, MA1, MA2> > >( test() );
+    return boost::report_errors();
+}

test/variant_visit.cpp

@@ -37,6 +37,10 @@ struct F
 
 int main()
 {
+    {
+        BOOST_TEST_EQ( (visit( []{ return 5; } )), 5 );
+    }
+
     {
         variant<int> v( 1 );
 

test/variant_visit_derived.cpp

@@ -0,0 +1,57 @@
+
+// Copyright 2017, 2020 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if defined(_MSC_VER)
+# pragma warning( disable: 4244 ) // conversion from float to int, possible loss of data
+#endif
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
+#include <utility>
+
+struct X: boost::variant2::variant<int, float>
+{
+#if BOOST_WORKAROUND( BOOST_MSVC, < 1930 )
+
+    template<class T> explicit X( T&& t ): variant( std::forward<T>( t ) ) {};
+
+#else
+
+    using variant::variant;
+
+#endif
+};
+
+template<class... T> struct Y: boost::variant2::variant<T...>
+{
+    using boost::variant2::variant<T...>::variant;
+};
+
+int main()
+{
+    {
+        X v1( 1 );
+        X const v2( 3.14f );
+
+        BOOST_TEST_EQ( (visit( []( int x1, float x2 ){ return (int)(x1 * 1000) + (int)(x2 * 100); }, v1, v2 )), 1314 );
+
+        visit( []( int x1, float x2 ){ BOOST_TEST_EQ( x1, 1 ); BOOST_TEST_EQ( x2, 3.14f ); }, v1, v2 );
+        visit( []( int x1, float x2 ){ BOOST_TEST_EQ( x1, 1 ); BOOST_TEST_EQ( x2, 3.14f ); }, std::move(v1), std::move(v2) );
+    }
+
+    {
+        Y<int, float> v1( 1 );
+        Y<int, float> const v2( 3.14f );
+
+        BOOST_TEST_EQ( (visit( []( int x1, float x2 ){ return (int)(x1 * 1000) + (int)(x2 * 100); }, v1, v2 )), 1314 );
+
+        visit( []( int x1, float x2 ){ BOOST_TEST_EQ( x1, 1 ); BOOST_TEST_EQ( x2, 3.14f ); }, v1, v2 );
+        visit( []( int x1, float x2 ){ BOOST_TEST_EQ( x1, 1 ); BOOST_TEST_EQ( x2, 3.14f ); }, std::move(v1), std::move(v2) );
+    }
+
+    return boost::report_errors();
+}

test/variant_visit_r.cpp

@@ -0,0 +1,98 @@
+
+// Copyright 2017 Peter Dimov.
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+#if defined(_MSC_VER)
+# pragma warning( disable: 4244 ) // conversion from float to int, possible loss of data
+#endif
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+using namespace boost::variant2;
+
+struct F1
+{
+    template<class T1> T1 operator()( T1 t1 ) const
+    {
+        return t1;
+    }
+};
+
+struct F2
+{
+    template<class T1, class T2> auto operator()( T1 t1, T2 t2 ) const -> decltype( t1 + t2 )
+    {
+        return t1 + t2;
+    }
+};
+
+struct F3
+{
+    template<class T1, class T2, class T3> auto operator()( T1 t1, T2 t2, T3 t3 ) const -> decltype( t1 + t2 + t3 )
+    {
+        return t1 + t2 + t3;
+    }
+};
+
+struct F4
+{
+    template<class T1, class T2, class T3, class T4> auto operator()( T1 t1, T2 t2, T3 t3, T4 t4 ) const -> decltype( t1 + t2 + t3 + t4 )
+    {
+        return t1 + t2 + t3 + t4;
+    }
+};
+
+int main()
+{
+    {
+        BOOST_TEST_EQ( (visit<int>( []{ return 3.14f; } )), 3 );
+    }
+
+    {
+        variant<int, float> v( 1 );
+
+        BOOST_TEST_EQ( visit<int>( F1(), v ), 1 );
+        BOOST_TEST_EQ( visit<float>( F1(), v ), 1.0f );
+    }
+
+    {
+        variant<int, float> const v( 3.14f );
+
+        BOOST_TEST_EQ( visit<int>( F1(), v ), 3 );
+        BOOST_TEST_EQ( visit<float>( F1(), v ), 3.14f );
+    }
+
+    {
+        variant<int, float> v1( 1 );
+        variant<int, float> const v2( 3.14f );
+
+        BOOST_TEST_EQ( visit<int>( F2(), v1, v2 ), 4 );
+        BOOST_TEST_EQ( visit<float>( F2(), v1, v2 ), 1 + 3.14f );
+    }
+
+    {
+        variant<int, float, double> v1( 1 );
+        variant<int, float, double> const v2( 3.14f );
+        variant<int, float, double> v3( 6.28 );
+
+        BOOST_TEST_EQ( visit<int>( F3(), v1, v2, v3 ), 10 );
+        BOOST_TEST_EQ( visit<float>( F3(), v1, v2, v3 ), static_cast<float>( 1 + 3.14f + 6.28 ) );
+    }
+
+    {
+        variant<int, float, double, char> v1( 1 );
+        variant<int, float, double, char> const v2( 3.14f );
+        variant<int, float, double, char> v3( 6.28 );
+        variant<int, float, double, char> const v4( 'A' );
+
+        BOOST_TEST_EQ( visit<int>( F4(), v1, v2, v3, v4 ), 10 + 'A' );
+        BOOST_TEST_EQ( visit<float>( F4(), v1, v2, v3, v4 ), static_cast<float>( 1 + 3.14f + 6.28 + 'A' ) );
+    }
+
+    return boost::report_errors();
+}