Bug in template parsing?

[Marcel Keller <M dot Keller at bristol dot ac dot uk>]

Hi,

Trying to compile the attached code with GCC 5.3.0 gives the error:

templ_bug.cpp: In function âvoid g()â:
templ_bug.cpp:15:12: error: expected primary-expression before â)â token
   T().f<t>();
            ^
templ_bug.cpp: In instantiation of âvoid g() [with T = A; int t = 0]â:
templ_bug.cpp:19:10:   required from here
templ_bug.cpp:15:8: error: invalid operands of types â<unresolved 
overloaded function type>â and âintâ to binary âoperator<â
   T().f<t>();
        ^

However, if I uncomment the commented line, it works fine. I cannot 
understand why this should make a difference. Is there a mistake in the 
code or a bug in GCC?

Best regards,
Marcel

#include <iostream>
using namespace std;

class A
{
public:
  template <int t> void f() { cout << "Hello world" << endl; }
};

//template <class T> void f();

template <class T, int t>
void g()
{
  T().f<t>();
}

int main() {
  g<A,0>();
}