MPark.Variant is an implementation of C++17 std::variant for C++11/14/17.

The implementation is based on my implementation of std::variant for libc++ and is continuously tested against libc++'s std::variant test suite.

New Features

• #56: Replaced the visitation mechanism to be switch-based.
  • Blog post: Variant Visitation V2
  • Thank you @quicknir for the contribution and collaboration on this effort!
• Improved visitor same return type error message:

error: static_assert failed due to requirement 'expected<int>::template but_got<double>()'
    "`visit` requires the visitor to have a single return type"

• Improved visitor exhaustiveness error message:

error: static_assert failed due to requirement
    'visitor<add_ints>::template does not handle<const int &, const int &>()'
    "`visit` requires the visitor to be exhaustive"

Bug Fixes

• Relational operators must return a type implicitly convertible to bool.
• #34: Support for pointers to incomplete types
• #41: Crash under MSVC (VS 2015 update 3)
• Visual Studio 2017 related issues:
  • #48: Fails to compile with MSVC 19.15
  • #49: Disable MPARK_CPP14_CONSTEXPR for MSVC <= 19.15
  • #55: Compilation failed in Visual Studio 2017
  • #57: Use constexpr compiler bug workaround for VS2017 version 15.9