[Concurrency] Non-Sendable value can be accessed from Global-Actor-isolated Task And normal Task

[kntkymt]

Description

Non-Sendable value can be accessed from Global-Actor-isolated Task And normal Task concurrently.

Reproduction

the following code can be complied with no error/warning on swift 6 mode

final class Counter {
    var count = 0
}

@MainActor
func f() {
    let c = Counter()

    Task {
        c.count += 1
        print(c.count)
    }

    Task.detached {
        c.count += 1
        print(c.count)
    }
}

Expected behavior

should not be compiled. since c would be concurrently accessed from Task and Task.detached.

Environment

$ swiftc --version

swift-driver version: 1.115 Apple Swift version 6.0 (swiftlang-6.0.0.9.10 clang-1600.0.26.2)
Target: arm64-apple-macosx14.0

Additional information

it seems that let c won't be sent into MainActor's region when capturing Task { }

final class Counter {
    var count = 0
}

@MainActor
func f() {
    // [(c), {(), MainActor}]
    let c = Counter()

    // should be: [{(c), MainActor}]
    // actual: [(c), {(), MainActor}]?
    Task {
        c.count += 1
        print(c.count)
    }

    // should be Conflict: [{(c), task}, {(c), MainActor}]
    // actual: [{(c), task}, {(), MainActor}]?
    Task.detached {
        c.count += 1
        print(c.count)
    }
}