SendableRegex.swift

/// A guaranteed-sendable regex type.
struct SendableRegex<Output>: RegexComponent, @unchecked Sendable {
  let regex: Regex<Output>
  init?(_ re: some RegexComponent<Output>) {
    if nil == re.regex._literalPattern { return nil }
    self.regex = re.regex
  }
}


// Usage:

import RegexBuilder

let simpleRegex = #/a+b*c/#
let complexRegex = Regex {
    OneOrMore { "a" }
    ZeroOrMore { "b" }
    TryCapture {
        OneOrMore(.digit)
    } transform: {
        Int($0)
    }
}

let sendableRegex = SendableRegex(simpleRegex)      // ok
let nonSendableRegex = SendableRegex(complexRegex)  // nil