templates

One C++17 problem I come across every now and then is to determine whether a certain class or function template specialization exists - say, for example, whether std::swap<SomeType> or std::hash<SomeType> can be used. I like to have solutions for these kind of problems in a template-toolbox, usually just a header file living somewhere in my project. In this article I try to build solutions that are as general as possible to be part of such a toolbox.

I recently needed to trace some error related to C++17 class template argument deduction and came across some corner cases. In this article, I document what I learned, show some “paradox” cases (which have nice, clean solutions as per the standard) and demonstrate a suspected Clang bug.