Construction of class creates unexpected function pointer [duplicate] - c++

Question

My issue is best demonstrated by the following code:
#include <fstream>
#include <iterator>
class Bar
{
public: template <class Iterator> Bar(Iterator first, Iterator last) {}
};
void foo(const Bar& bar) { }
int main(int argc, char** argv)
{
std::ifstream file("file.txt");
Bar bar(std::istream_iterator<char>(file), std::istream_iterator<char>());
foo(bar); // error C2664: 'foo' : cannot convert parameter 1 from 'Bar (__cdecl *)(std::istream_iterator<_Ty>,std::istream_iterator<_Ty> (__cdecl *)(void))' to 'const Bar &'
// with
// [
// _Ty=char
// ]
// Reason: cannot convert from 'overloaded-function' to 'const Bar'
// No constructor could take the source type, or constructor overload resolution was ambiguous
return 0;
};
Here are some similar instantiations of bar that don't cause the same ambiguity:
Bar bar = Bar(std::istream_iterator<char>(file), std::istream_iterator<char>());
and
std::istream_iterator<char> start(file);
std::istream_iterator<char> end;
Bar bar(start, end);
My question is, what is it about the first declaration of bar that causes it to be misinterpreted?
note: I'm testing with Visual Studio 2010 (10.0.30319.1)

Answer 1

ArunMu gets partial credit, it is indeed an example of Most Vexing Parse, but that term was coined in Meyer's Effective STL (Chapter 1, Item 6) not Exceptional C++.
It is being interpreted as a function pointer (the (__cdecl *) portion of the error is a dead give away), and apparently the C++ standard requires it to be interpreted that way. Does anyone have a chapter/verse citation for that?
There is also a another solution to provide a disambiguation. Adding an additional set of parenthesis around each parameter works too:
Bar bar( (std::istream_iterator<char>(file)), (std::istream_iterator<char>()) );
It's also worth pointing out that the issue is unrelated to the templates, as I had originally thought.

Answer 2

I think it is related to "C++ most vexing parse" that you will find in Meyer's Effective STL book.
Bar bar(std::istream_iterator&lt char &gt(file), std::istream_iterator &lt char &gt());
Is being considered as a **function declaration.**
due to which in foo(bar); you are sending a function pointer instead :)
Doing like below will have no error:
Bar bar = Bar(//your arguments here);
foo(bar);