Closed
Description
Describe the bug
Code utilizing Sequence and Iterator protocols that worked in previous versions of Swift no longer type-checks in 5.7 snapshots.
Steps To Reproduce
Try to build WasmTransformer with Xcode 14.0 beta 5.
Expected behavior
This code type-checks and builds as it did Swift 5.5/5.6
Screenshots
Environment (please fill out the following information)
- OS: macOS 12.5 and Ubuntu 20.04
- Xcode Version/Tag/Branch: 14.0 beta 5 (14A5294e), also reproducible on Linux with
swiftlang/swift:nightly-5.7-focalimage and6fa8c6b08e85hash.
Additional context
Here's the code snippet (not self-contained, but I hope it helps to pinpoint the issue) that causes these new errors:
public protocol VectorSectionReader: Sequence where Element == Result<Item, Error> {
associatedtype Item
var count: UInt32 { get }
mutating func read() throws -> Item
}
public struct VectorSectionIterator<Reader: VectorSectionReader>: IteratorProtocol {
private(set) var reader: Reader
private(set) var left: UInt32
init(reader: Reader, count: UInt32) {
self.reader = reader
self.left = count
}
private var end: Bool = false
public mutating func next() -> Reader.Element? {
guard !end else { return nil }
guard left != 0 else { return nil }
let result = Result(catching: { try reader.read() })
left -= 1
switch result {
case .success: return result
case .failure:
end = true
return result
}
}
}
extension VectorSectionReader {
__consuming public func makeIterator() -> VectorSectionIterator<Self> {
VectorSectionIterator(reader: self, count: count)
}
public func collect() throws -> [Item] {
var items: [Item] = []
items.reserveCapacity(Int(count))
for result in self {
try items.append(result.get())
}
return items
}
}