swl::optional

A standard conforming C++20 implementation of std::optional.

C++20 came with new features that makes the implementation of std::optional (and other types based on unions) a lot simpler to write, faster to compile, and more debugger-friendly (ever crawled through all the std::optional base classes in your IDE debugger?).
So if you're using optionala lot in C++20, switching to this implementation is free cookies.

Testing

The tests were adapted from TartanLlama's optional with some bits from the LLVM repo. Kudos to them.
To run the tests :
mkdir ./test_out
cd test_out
cmake ../
ctest --build-and-test ../ ./ --build-generator "Unix Makefiles" (replace "Unix Makefiles" as needed)
make test

Tested compilers

• GCC 11+
• GCC 10+ (the early 10.X versions have a bug in std::construct_at, which prevent to use it in a constexpr context, hence the tests might not compile)
• Clang will not fully work as its implementation of C++20 is still incomplete (Clang 12+ will work for trivially destructible type)