http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0380r1.pdf

2019
http://llvm.org/devmtg/2019-04/slides/Poster-Lopez-Gomez-Adding_support_for_C++_contracts_to_Clang.pdf
https://habr.com/ru/post/443766/
Fahler - Programming with Contracts in C++20
    https://www.youtube.com/watch?v=0eLcSXPECa0
2018
https://www.fi.muni.cz/%7Extusil/cpp-contracts-1.html

https://github.com/arcosuc3m/clang-contracts