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.
Unify the mutable iterators too. Switch the ListInsertion trait to use
method .insert_next() and .peek_next() for list mutation. .insert_next()
inserts an element into the list that will not appear in iteration, of
course; so the length of the iteration can not change during iteration.
Did not properly allow runs from the `other` list to be merged in. The
test case was using a wrong expected value.
Edited docs for merge so they explain more clearly what it does.
Also make sure insert_ordered is marked pub.
An iterator that allows mutating the list is very useful but needs care
to not be unsound. ListIteration exposes only insert_before (used for
insert_ordered) and peek_next so far.
This is an owned sendable linked list which allows insertion and
deletion at both ends, with fast traversal through iteration, and fast
append/prepend.
It is indended to replace the previous managed DList with exposed list
nodes. It does not match it feature by feature, but DList could grow
more methods if needed.
the `test/run-pass/class-trait-bounded-param.rs` test was xfailed and
written in an ancient dialect of Rust so I've just removed it
this also removes `to_vec` from DList because it's provided by
`std::iter::to_vec`
an Iterator implementation is added for OptVec but some transitional
internal iterator methods are still left
