c++ - template argument deduction/substitution failed, when using std::function and std::bind

I have a compile error when using std::function in a templated member function, the following code is a simple example:

#include 
#include 
using std::function;
using std::bind;
using std::shared_ptr;

class Test {

public:
     template 
     void setCallback(function cb); 
};

template 
void Test::setCallback(function cb)
{
    // do nothing
}


class TestA {
public:
    void testa(int a, int b) {   }
};


int main()
{
    TestA testA;

    Test test;
    test.setCallback(bind(&TestA::testa, &testA, std::placeholders::_1, std::placeholders::_2));
    return 0;
}

And come with the following compile error:

testtemplate.cpp: In function ‘int main()’:

testtemplate.cpp:29:92: error: no matching function for call to
‘Test::setCallback(std::_Bind_helper)(int, int),
TestA, const std::_Placeholder<1>&, const
std::_Placeholder<2>&>::type)’

testtemplate.cpp:29:92: note: candidate is: testtemplate.cpp:10:7:
note: template void Test::setCallback(std::function)

testtemplate.cpp:10:7: note: template argument

deduction/substitution failed:

testtemplate.cpp:29:92: note: ‘std::_Bind(TestA*, std::_Placeholder<1>,
std::_Placeholder<2>)>’ is not derived from ‘std::function’

I'm using C++11 and g++ 4.7

Answer

To figure out the problem let separate statements:

auto f = bind(&TestA::testa, &testA, _1, _2); // OK
test.setCallback(f);                          // <<--- Error is here

setCallback needs to know type of T and it can't deduce it from f, so give it a type

test.setCallback(f); // TYPE: int, float, a class, ...