According to std-specify-language-standard-version for VS2017 -
By default, /std:c++14 is specified, which disables language and standard library features found in later versions of the C++ language standard. Use /std:c++17 to enable C++17 standard-specific features and behavior. To explicitly enable the currently implemented compiler and standard library features proposed for the next draft standard, use /std:c++latest. All C++20 features require /std:c++latest; when the implementation is complete, a new /std:c++20 option will be enabled.