sending closure parameter function used in top-level can't catch cross border.

[carlhung]

Description

sending closure parameter function used in top-level can't catch cross border.

Reproduction

public final class NonSendable {
  var value = 0
}

func f4(_ closure: sending @escaping () async -> Void) {
  Task.detached {
    await closure()
  }
}

do {
    let nonSendable = NonSendable()
    f4 {
      nonSendable.value = 0
        print(nonSendable.value)
      
    }
    // it should not be able to assign a new value.
    nonSendable.value = 0
    print(nonSendable.value)
}

Expected behavior

showing an error.

Environment

Swift version 6.0.1 (swift-6.0.1-RELEASE) Target: aarch64-unknown-linux-gnu

Additional information

No response

[jamieQ]

associated forum discussion: https://forums.swift.org/t/sending-closure/76780