(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?
···
On Jun 29, 2016, at 12:34 PM, Dave Abrahams <dabrahams@apple.com> wrote:
on Wed Jun 29 2016, David Sweeris <davesweeris-AT-mac.com> wrote:
Would adding a "init(_: T.self) {...}" solve that issue?
? I don't see how.
Sent from my iPhone
On Jun 29, 2016, at 01:54, Dave Abrahams via swift-evolution <swift-evolution@swift.org> wrote:
My worry is that people will write
MemoryLayout(Int.self).size
when they mean
MemoryLayout<Int>.size
(often because for some reason they don't like angle brackets).
I prefer to make the uncommon case much harder to write.
--
Dave
- Dave Sweeris
