Array<T> not Encodable - error at runtime, not compile time?

Using Swift
1

Hi,

This error makes perfect sense, but I’m surprised it's a runtime error. I expected it at compile time. Am I doing something wrong? Is this on the type system to-do list?

  let c = JSONEncoder()
  struct Foo { … }
  let fs: [Foo] = [ Foo(...) ]
  let data = try! c.encode(fs) // Didn’t think this would compile

The runtime error is: fatal error: Array<Foo> does not conform to Encodable because Foo does not conform to Encodable.

Rob

2

Hi Robert,

When the conditional conformance feature arrives in Swift, it will allow us to express `extension Array : Encodable where Element : Encodable` and `extension Array : Decodable where Element : Decodable`.
At the moment, this isn’t possible, so `Array` is unconditionally `Codable` and the failure happens at runtime. This will be a compile-time error in a future version of Swift.

— Itai

···

On 26 Oct 2017, at 9:47, Robert Nikander via swift-users wrote:

Hi,

This error makes perfect sense, but I’m surprised it's a runtime error. I expected it at compile time. Am I doing something wrong? Is this on the type system to-do list?

  let c = JSONEncoder()
  struct Foo { … }
  let fs: [Foo] = [ Foo(...) ]
  let data = try! c.encode(fs) // Didn’t think this would compile

The runtime error is: fatal error: Array<Foo> does not conform to Encodable because Foo does not conform to Encodable.

Rob_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users

3

Makes sense. Thanks!

···

On Oct 26, 2017, at 1:01 PM, Itai Ferber <iferber@apple.com> wrote:

Hi Robert,

When the conditional conformance feature arrives in Swift, it will allow us to express extension Array : Encodable where Element : Encodable and extension Array : Decodable where Element : Decodable.
At the moment, this isn’t possible, so Array is unconditionally Codable and the failure happens at runtime. This will be a compile-time error in a future version of Swift.

— Itai

On 26 Oct 2017, at 9:47, Robert Nikander via swift-users wrote:

Hi,

This error makes perfect sense, but I’m surprised it's a runtime error. I expected it at compile time. Am I doing something wrong? Is this on the type system to-do list?

let c = JSONEncoder()
struct Foo { … }
let fs: [Foo] = [ Foo(...) ]
let data = try! c.encode(fs) // Didn’t think this would compile

The runtime error is: fatal error: Array<Foo> does not conform to Encodable because Foo does not conform to Encodable.

Rob_______________________________________________
swift-users mailing list
swift-users@swift.org <mailto:swift-users@swift.org>
https://lists.swift.org/mailman/listinfo/swift-users