debug deduced type?

Would it be possible to output what a deduced type looks like? 

E.g. for lambda, I'm thinking something like:

auto f = [f=4](char){};
using f_type = std::decay<decltype(f)>::type;

constexpr {
    compiler.debug($f_type);
}

Or for templates:

template <typename T>
void func() {
    constexpr {
        compiler.debug($T);
    }
}