There are many cases in C++ where the type is unspecified (std::bind for example), or even is unutterable (lambdas, or unnamed structures). I think F-strings w

There are many cases in C++ where the type is unspecified (std::bind for example), or even is unutterable (lambdas, or unnamed structures). I think F-strings would be an example of the latter. You can always box of course (std::function, std::any at the limit), but it has a non-trivial cost.