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 build all the tests, compile ./tests/test_main.cpp including the root of the repository in the search path, e.g. :
g++ -std=c++20 ./tests/test_main.cpp -I .

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)