Confusing Template error

Question

I\'ve been playing with clang a while, and I stumbled upon \"test/SemaTemplate/dependent-template-recover.cpp\" (in the clang distribution) which is supposed to provide hint

Answer 1

Excerpt from C++ Templates

The .template Construct A very similar problem was discovered after the introduction of typename. Consider the following example using the standard bitset type:

template 
void printBitset (std::bitset const& bs) 
{ 
    std::cout << bs.template to_string, 
                                       allocator >(); 
} 

The strange construct in this example is .template. Without that extra use of template, the compiler does not know that the less-than token (<) that follows is not really "less than" but the beginning of a template argument list. Note that this is a problem only if the construct before the period depends on a template parameter. In our example, the parameter bs depends on the template parameter N.

In conclusion, the .template notation (and similar notations such as ->template) should be used only inside templates and only if they follow something that depends on a template parameter.