Here are the story. I updated my library yesterday and found some of bugs with Swift 5.
These are the part of code that reproduce the problem.
public protocol ScalarProtocol: ScalarMultiplicative where Self == Scalar {
}
public protocol ScalarMultiplicative : AdditiveArithmetic {
associatedtype Scalar : ScalarProtocol
}
public protocol MapReduceArithmetic : ScalarMultiplicative, Collection where Element : ScalarMultiplicative, Scalar == Element.Scalar {
func map(_ transform: (Element) -> Element) -> Self
func reduce<Result>(_ initialResult: Result, _ nextPartialResult: (Result, Element) -> Result) -> Result
func reduce<Result>(into initialResult: Result, _ updateAccumulatingResult: (inout Result, Element) -> ()) -> Result
}
extension Collection where Self : MapReduceArithmetic {
public func reduce<Result>(_ initialResult: Result, _ nextPartialResult: (Result, Element) -> Result) -> Result {
return self.reduce(into: initialResult) { $0 = nextPartialResult($0, $1) }
}
}
The protocol MapReduceArithmetic is an implementation details and provide a default operators implementation. You can found the example in here.
https://github.com/SusanDoggie/Doggie/blob/swift-5/Sources/Doggie/Maths/Arithmetic.swift
However, if i create a new protocol base on MapReduceArithmetic and limiting with Element == Scalar.
The compiler is going wrong.
public protocol Tensor : MapReduceArithmetic where Scalar : BinaryFloatingPoint, Element == Scalar, Index == Int {
var magnitude: Scalar { get set }
}
extension Tensor {
public var magnitude: Scalar {
return self.reduce(0) { $0 + $1 * $1 }.squareRoot()
}
}
Is that bugs of compiler? If yes, i will file this bug later.
also i reported other bugs which may related to this.
https://bugs.swift.org/browse/SR-10022
https://bugs.swift.org/browse/SR-10023