minimal c++ for https://stackoverflow.com/questions/62447159/mixing-templates-with-stdenable-if-t-and-specialisation

main.cpp

#include <string>
#include <type_traits>

template<typename T, typename R> 
R do_foo(T bb)
{
  static_assert(std::is_same<T, void>::value && false, "No use here");   
}

template<typename T, typename R>
std::enable_if_t<std::is_same<R, std::string>::value, R> do_foo(T bb)
{
    return "Boots";
}

template<>
bool do_foo(int bb)
{
    return false;
}

int main()
{
    do_foo<std::string, std::string>(std::string());
    return 0;
}