How do template aliases affect template parameter deduction?

Question

In C++03, template parameter deduction does not occur in some contexts. For example:

template  struct B {};

template 
st         


        

Answer 1

Imagine this:

template  struct Foo { typedef   T type; }
template <> struct Foo     { typedef int type; }

template  using mytype = typename Foo::type;

template  void f(mytype);

Now if I want int n; f(n);, how could I decide whether I want T = int or T = char? The whole problem, which is unaffected by template aliases, is that you cannot deduce backwards to all the things that could possibly define something.