id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
7378	lookup_one_property fails if property tag not found	Andreas Hehn <hehn@…>	Douglas Gregor	"{{{boost::lookup_one_property<PropertyList,Tag>::found}}} does not compile if {{{Tag}}} is not found in the {{{PropertyList}}}.

The problem originates from the {{{lookup(...)}}} function definition in the template specialization
{{{
  template <typename Tag, typename T, typename Base, typename PropName>
  struct lookup_one_property_internal<boost::property<Tag, T, Base>, PropName>: lookup_one_property_internal<Base, PropName> {
    private:
    typedef lookup_one_property_internal<Base, PropName> base_type;
    public:
    template <typename PL>
    static typename enable_if<is_same<PL, boost::property<Tag, T, Base> >, typename base_type::type&>::type
    lookup(PL& prop, const PropName& tag)
}}}
which requires the base class to provide a {{{type}}} member.

If the tag is not found the unspecialized template
{{{
    template <typename PList, typename PropName, typename Enable = void>
    struct lookup_one_property_internal {BOOST_STATIC_CONSTANT(bool, found = false);};
}}}
will be instantiated as Base where the compiler can't find any {{{type}}} member."	Bugs	closed	To Be Determined	graph	Boost 1.52.0	Problem	fixed	lookup_one_property property_value