id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
11993	Add a default constructor to intrusive unordered_set and unordered_multiset	anonymous	Ion Gaztañaga	"All the constructors of intrusive `unordered_set` and `unordered_multiset` require a `bucket_traits`. It is currently not possible to instantiate an `unordered_set` without having allocated some buckets.

It would be useful to add a default constructor to `unordered_set` and `unordered_multiset`. That would allow to create hash containers that allocate buckets lazily at the first element insertion.

That would also allow this kind of pattern:
{{{#!c++
unordered_set<MyType, ...> v;
if (some_condition) {
  v = some_collection();
} else {
  v = some_other_collection();
}
}}}

Bonus if the const methods of a default-constructed unordered_set/unordered_multiset can be called and behave as an empty collection (in particular `empty`, `size`, `begin`/`cbegin`, `end`/`cend`, `count`, `find` and `equal_range`)."	Feature Requests	closed	To Be Determined	intrusive	Boost 1.60.0	Problem	wontfix