Bug in move assignment

[serges147]

Here is current code of the move assignment:

    auto operator=(Node&& other) noexcept -> Node&
    {
        moveFrom(other);
        return *this;
    }

The moveFrom private helper is built in assumption (with corresponding assert!) that this node is un-linked b/c it...

1. either never been linked - just being constructed (see move ctor)
2. or, were properly removed first from a tree, and now ready to be reassigned (see move assignment operator)

So, for the case # 2 (operator=(Node&&) there should be also conditional node removal (in case it's linked to a tree), like this:

    auto operator=(Node&& other) noexcept -> Node&
    {
        if (isLinked())
        {
            remove();
        }
        moveFrom(other);
        return *this;
    }

Such fix requires refactoring of Node::remove methods to make them non-static, and not requiring initial origin argument, so that method prototype will be like this:

    void remove() const noexcept
    {
        removeImpl(this);
    }
    void remove() noexcept
    {
        removeImpl(this);
        unlink();
    }

, and private static removeImpl will be very close to current algorithm with minor changes so that neither initial origin nor root knowledge is required (deduced from context instead).

[serges147]

Resolved by PR #17 - closing