id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
4910	ambiguity of operator<< in display_expr	Maxim Yanchenko <Maxim.Yanchenko@…>	Eric Niebler	"from here:
http://cpp-next.com/archive/2010/09/expressive-c-playing-with-syntax/comment-page-1/#comment-1134

{{{#!c++
struct A {};
struct B:A {};
std::ostream& operator<<( std::ostream& out, const A& ) { return out << ""this is A!""; }
}}}
If you do

{{{#!C++
proto::display_expr( map( A(), 1 ) );
}}}

it works, but if you do

{{{#!cpp
proto::display_expr( map( B(), 1 ) );
}}}

it doesn't compile due to ambiguity introduced by `hidden_detail_::operator<<` that does this nice typeid output.

The patch for `boost/proto/debug.hpp` against 1.44.0 (works for me) and last revision 66440 (not tried to compile, just by analogy) is attached."	Patches	closed	To Be Determined	proto	Boost Development Trunk	Problem	fixed