Cannot invoke initializer for type 'Range' with an argument list of type '(Range)'

Question

After updating to Xcode 10 beta, which apparently comes with Swift 4.1.50, I\'m seeing the following error which I\'m not sure how to fix:

Cannot invo

Answer 1

Some background:

In Swift 3, additional range types were introduced, making a total of four (see for example Ole Begemann: Ranges in Swift 3):

Range, ClosedRange, CountableRange, CountableClosedRange

With the implementation of SE-0143 Conditional conformances in Swift 4.2, the “countable” variants are not separate types anymore, but (constrained) type aliases, for example

 public typealias CountableRange = Range
      where Bound.Stride : SignedInteger

and, as a consequence, various conversions between the different range types have been removed, such as the

init(_ other: Range)

initializer of struct Range. All theses changes are part of the [stdlib][WIP] Eliminate (Closed)CountableRange using conditional conformance (#13342) commit.

So that is the reason why

let range: Range = Range(start..

does not compile anymore.

How to fix

As you already figured out, this can be simply fixed as

let range: Range = start..

or just

let range = start..

without the type annotation.

Another option is to use a one sided range (introduced in Swift 4 with SE-0172 One-sided Ranges):

extension String {
    func index(of aString: String, startingFrom position: Int = 0) -> String.Index? {
        let start = index(startIndex, offsetBy: position)
        return self[start...].range(of: aString, options: .literal)?.lowerBound
    }
}

This works because the substring self[start...] shares its indices with the originating string self.