[matt-edmondson]

The README teaches clone.Items.DeepCloneFrom(Items) for get-only collection properties. That pattern needs ICollection<T> or IDictionary<TKey, TValue>. Stack<T>, Queue<T>, ConcurrentStack<T> and ConcurrentQueue<T> implement neither, so it failed with CS1929. The workaround most people reach for, pushing each item of Undo.DeepClone(), compiles but reverses the stack.

This adds four in-place DeepCloneFrom overloads. Each one:

• snapshots source first, so x.DeepCloneFrom(x) leaves x unchanged (the DeepCloneFrom empties the destination when dest and source are the same collection instance #64 self-clone safety)
• clears dest and refills it with deep clones, keeping the source order: a stack still pops in the same order, and a queue still dequeues in the same order

Per-type details:

• Stack<T>: pushes the snapshot in reverse.
• ConcurrentStack<T>: builds the reversed clones first, then calls Clear and PushRange.
• ConcurrentQueue<T>: calls Clear on netstandard2.1 and .NET. netstandard2.0 has no Clear, so it drains with TryDequeue instead.

The remarks note that on the concurrent types, clear-and-refill isn't atomic.

ConcurrentBag<T> is left out on purpose. It has no defined order, and the issue lists it as optional.

The README's DeepCloneFrom table now lists the new receivers.

Tests

New InPlaceStackQueueTests:

• For each type, the clone pops or dequeues in the source order, every item is a distinct instance, and existing contents of dest are replaced.
• Self-clone leaves each of the four collections unchanged.
• A DeepCloneable with get-only Stack<T> and ConcurrentQueue<T> properties uses the README pattern, and its clone has the right order.

Validation:

• With the library change stashed, the test project fails to compile with CS1929 on all four receiver types.
• With the change, all 72 tests pass on net10.0.
• The library builds for netstandard2.0, netstandard2.1, net8.0, net9.0 and net10.0.

Fixes #114

---

Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud