Regex is not Sendable

[svanimpe]

Description

I was surprised to learn that Regex is not Sendable. The code below doesn't compile with Swift 6.

Reproduction

struct Parser {
    private static let number = /\d+/
}

Expected behavior

I would expect this to just work. Regex is a value type. Why would it have shared mutable state?

Environment

swift-driver version: 1.115 Apple Swift version 6.0.2 (swiftlang-6.0.2.1.2 clang-1600.0.26.4)
Target: x86_64-apple-macosx15.0

Additional information

No response