Is sort() stable in Swift 5?

[xwu (Xiaodi Wu)]

Assigning a dictionary without re-hashing

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. (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.)