How to call a templated function if it exists, and something else otherwise?

Question

I want to do something like

template 
void foo(const T& t) {
   IF bar(t) would compile
      bar(t);
   ELSE
      baz(t);
}

Answer 1

Are you not able to use full specialisation here (or overloading) on foo. By say having the function template call bar but for certain types fully specialise it to call baz?