Unexpected compiler error when passing function as parameter to rethrows function

[Wouter01]

Description

When passing a function as a parameter to a rethrows function instead of providing a closure, an unexpected compiler error is thrown, stating that the function call can throw, which is not the case. Calling the same function from within a closure is ok. The error does not seem to occur when @MainActor attribute is removed from the function. This error does not occur on Swift 5.10.

Reproduction

@MainActor
func doSomethingOne() {
    func test(_ tab: Int) {}

    [1,2,3].forEach(test) // Call can throw, but it is not marked with 'try' and the error is not handled
                          // Call is to 'rethrows' function, but argument function can throw
}

@MainActor
func doSomethingTwo() {
    func test(_ tab: Int) {}

    for i in [1,2,3] {
        test(i) // OK
    }
}

func doSomethingThree() {
    func test(_ tab: Int) {}

    [1,2,3].forEach(test)  // OK
}

Expected behavior

The code compiles

Environment

swift-driver version: 1.109.2 Apple Swift version 6.0 (swiftlang-6.0.0.3.300 clang-1600.0.20.10)
Target: arm64-apple-macosx15.0

Additional information

Edit: This only seems to occur when Swift 6 language mode is enabled

[nh7a]

This is still the case with Xcode 16 beta 3.

swift-driver version: 1.111.2 Apple Swift version 6.0 (swiftlang-6.0.0.5.15 clang-1600.0.22.6)

[DagAgren]

Seeing the same issue. Also, at least in my case changing it to [1,2,3].forEach { test($0) } also makes the error go away, so this seems like a clear bug.

[AdamCmiel]

Seeing the same behavior building on ce29eca81a5