[swift-evolution] struct subtyping

James Campbell james at supmenow.com
Thu Mar 24 10:52:53 CDT 2016

Would love a way of extending an existing struct as a new type but it not
being related to the struct it extends.

Sort of like a mixin but for structs, so I could have:

struct Object {
let identifier: String

struct User: Object {


struct Tree: Object {

The last two structs get the identifier property "mixed" in but are unique
types :)


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On Thu, Mar 24, 2016 at 2:16 PM, Tino Heth via swift-evolution <
swift-evolution at swift.org> wrote:

> > Could we accomplish something similar to `newtype` by making the
> `typealias` declaration more powerful?
> It's the first thing I tried, but afair someone from the Core Team opposed
> extending typealias - and I had to agree that an "alias" should be just a
> synonym.
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