URL.init?(string: String) returns 'nil' when it shouldn't

Question

I'm experiencing an issue with the Foundation struct URL's string initializer. I'll post some code from the repl below:

Welcome to Apple Swift version 5.1 (swiftlang-1100.0.270.13 clang-1100.0.33.7).
Type :help for assistance.
  1> import Foundation
  2> let testString = "https://www.apple.com"
testString: String = "https://www.apple.com"
  3> let testUrl1 = URL(string: testString)
testUrl1: URL? = nil
  4> let testUrl2 = URL(string: "https://www.apple.com")
testUrl2: URL? = nil

I cannot think of why this is happening, if you look at the source for the initializer, located at https://github.com/apple/swift-corelibs-foundation/blob/master/Foundation/URL.swift#L495 you'll see this in the documentation:

/// Initialize with string.
///
/// Returns `nil` if a `URL` cannot be formed with the string (for example, if the string contains characters that are illegal in a URL, or is an empty string).

As far as I can tell though, the string I am testing with is a valid URL and the initializer shouldn't be returning nil. I have tried this on two different Macs and in a freshly installed virtual machine, and have gotten the same result in all of them. macOS 10.15, Xcode 11.1. Anyone have any insight into what might be wrong?

Answer 1

It would appear to be a REPL issue and existed in 11.0, too. But if you print(testUrl1), you’ll see it really is set.