Assigning a dictionary without re-hashing

[lorentey (Karoy Lorentey)]

@xwu

Can we formalize this guarantee?

Absolutely. This is a (semantic) API change, so I expect it'll require going through Swift Evolution. I've been collecting other ill-defined aspects of the stdlib -- perhaps we have a large enough batch of these now to be worth the expense of a small proposal.

Regression in Set with Swift 5.5

That would be an excellent idea! Are you volunteering to write it up? So right now we have: Sequence.sorted(), .sorted(by:), MutableCollection.sort(), .sort(by:) should document that the sort algorithm is stable. (Starting from Swift x.y) Set.union(_:), Set.intersection(_:), and Set.formIntersection(_:) (all overloads) should document that members of the result that appear in both inputs are taken from self. (Interestingly, formUnion already has this guarantee.) (Starting from Swift 5.6) A…

(Edit: unifying and documenting the expected behavior of base properties on mutable slices could also be part of this, although that one also requires actual behavioral changes in some obscure corners of the stdlib.)