Factor out internal methods to pop/push list nodes so that .merge() and .rotate_to_front(), .rotate_to_back() (new methods) can be implemented without allocating nodes.
With that, some cleanup changes to DList use of Option, and adding a missing Encodable implementation.
SmallIntSet is equivalent to BitvSet but with 64 times the memory
overhead. There's no reason for it to exist.
SmallIntSet's overhead should really only be 8 times, but for some
reason, `sys::size_of::<Option<()>>() == 8`, not 1.
Switched Bitv and BitvSet to external iterators. They still use some internal iterators internally (ha).
Derived clone for all Bitv types.
Removed indirection in BitvVariant. It previously held a unique pointer to the appropriate Bitv struct, even though those structs are the size of a pointer themselves. BitvVariant is the same size (16 bytes) as it was previously.
.peek_next() needs to check the element counter just like the .next()
and .next_back() iterators do.
Also clarify .insert_next() doc w.r.t double ended iteration.
Made the `iter` and `mut_iter` methods on SmallIntMap and SmallIntSet return double-ended-iterators. These iterators now implement `size_hint`.
Also the iterator tests only tested dense maps/sets, which aren't very useful. So they were changed to iterate over sparse maps/sets.
Fixes#7721
Factor out internal methods for pop/push ~Node<T>, This allows moving
nodes instead of destructuring and allocating new.
Make use of this in .merge() so that it requires no allocations when
merging two DList.
Implement method .cycle() that repeats an iterator endlessly
Implement Clone for simple iterators (without closures), including VecIterator.
> The theory is simple, the immutable iterators simply hold state
> variables (indicies or pointers) into frozen containers. We can freely
> clone these iterators, just like we can clone borrowed pointers.
Updated all users of HashMap, HashSet ::consume() to use
.consume_iter().
Since .consume_iter() takes the map or set by value, it needs awkward
extra code to in librusti's use of @mut HashMap, where the map value can
not be directly moved out.
Addresses issue #7719
