class/fun templates + decltype/decltype(auto) + one screen program = CRASH

[edwdmkrv]

This example causes https://cppinsights.io/ 's crash with different ways depending on how many lines in main() are commented. It is impossible to uncomment even a single line in main() without causing a crash.
The code compiles and works at least here.
The origin of the code is mentioned here, the first link in the article (which is translated by Google). I just removed "using namespace std;" from the original code, and corrected the affected part of the code by adding "std::" prefix where necessary.