on Wed Jun 29 2016, David Sweeris <davesweeris-AT-mac.com> wrote:
> (While I was typing this up, I realized that the exact usage you’re
> worried about, “MemoryLayout(Int.self).size” won’t compile, since
> `MemoryLayout` currently doesn’t have instance properties. If you’re
> worried about someone incorrectly typing out
> “MemoryLayout(Int.self).dynamicType.size”, though…)
>
> I made a rather critical typo in my earlier reply. It should’ve been
> “init(_: T.Type)”, instead of “init(_: T.self)”, which is to say this:
> extension MemoryLayout { // assuming `MemoryLayout<T>` is already defined as
> proposed
> public init(_ : T.Type) {} // makes it so that `MemoryLayout(T.self)`
> still has the correct type for `T`
> }
>
> Here are the results of some quick playgrounding in the WWDC Xcode 8 beta:
> // without `init(_ : T.Type)` defined
> MemoryLayout<Int8>.size // 1, correct
> MemoryLayout(Int8.self).dynamicType.size // 8, almost certainly wrong
> //MemoryLayout(Int8).dynamicType.size // error
> MemoryLayout(0 as Int8).dynamicType.size // 1, correct
> MemoryLayout<Int8.Type>.size // 8, correct
> MemoryLayout(Int8.Type.self).dynamicType.size // 8, correct, but is oddly
> worded
> //MemoryLayout(Int8.Type).dynamicType.size // error
>
> // with `init(_ : T.Type)` defined
> MemoryLayout<Int8>.size // 1, correct
> MemoryLayout(Int8.self).dynamicType.size // 1, almost certainly correct
> MemoryLayout(Int8).dynamicType.size // 1, almost certainly correct
> MemoryLayout(0 as Int8).dynamicType.size // 1, correct
> MemoryLayout<Int8.Type>.size // 8, correct
> MemoryLayout(Int8.Type.self).dynamicType.size // 8, correct, but is oddly
> worded
> MemoryLayout(Int8.Type).dynamicType.size // 8, correct
>
> The only value that changes (aside from the errors) is the one “typo” that
> you were worried about.
>
> Do this change your mind?
No; it's too tricky. In your design MemoryLayout(x) now has two
different meanings depending on the type of x.
--
Dave
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