[swift-evolution] [Discussion] Seal `T.Type` into `Type<T>`

Adrian Zubarev adrian.zubarev at devandartist.com
Wed Jul 13 07:02:26 CDT 2016

This isn’t a full proposal (yet). We still can change things. I didn’t consider everything and can’t to that on my own. Feedback is welcome.

To answer your question, we still need the metatype to access initializer and static member of that type. If we’d drop T.Type completely, we’d lose functionality to do so.

protocol A {

func foo<T : A>(metatype: T.Type) -> T {
    return metatype.init()
The downside of this proposal is the bottleneck property to access that functionality, otherwise adding Hashable or other things like size (MemoryLayout) won’t be possible without serious compiler magic. So do I believe.

func foo<T : A>(type: Type<T>) -> T {
    return type.metatype.init()
This is huge tradeoff, but it’s worth considering if the community can life with that.

Furthermore as already been mentioned in this thread, we might consider to extend Type<T> to add reflection functionality to it. (If we’d decide to go in that direction.)

Adrian Zubarev
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Am 13. Juli 2016 um 13:15:02, Anton Zhilin (antonyzhilin at gmail.com) schrieb:

Why can't we drop metatypes T.Type with your proposal? Do they bring some extra capabilities over Type<T> struct? 
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