C++17 std::variant not behaving as expected with custom visitor and nested variants
I've tried everything I can think of but I tried several approaches but none seem to work. I'm working on a personal project and I'm working on a C++17 project where I'm using `std::variant` to create a type-safe union of multiple types. However, I'm working with unexpected behavior when applying a custom visitor to a nested `std::variant`. Here's a simplified version of my code: ```cpp #include <iostream> #include <variant> #include <string> using namespace std; struct Visitor { void operator()(int i) const { cout << "Integer: " << i << endl; } void operator()(const string& s) const { cout << "String: " << s << endl; } }; int main() { using nested_variant = std::variant<int, std::variant<std::string, double>>; nested_variant nv = std::variant<std::string, double>{"Hello"}; Visitor visitor; std::visit(visitor, nv); return 0; } ``` In this case, I expect the output to be `String: Hello`, but I am getting an behavior: ``` behavior: no matching function for call to 'std::visit' ... ``` It seems that the visitor is not able to handle the nested variant correctly. I've tried creating separate visitors for the nested variant, but that leads to additional complexity. I'm also unsure if my use of `std::variant` is optimal here, especially with the nesting. Could someone provide guidance on how to correctly implement visiting for nested variants or if there's a better design pattern I should consider for handling these types? Any insights would be greatly appreciated! I'd really appreciate any guidance on this. I'm developing on Debian with C++. Am I missing something obvious?