Task created from a method with an isolated parameter breaks actor isolation

[dfed]

Description
A Task created from a method that executes within the isolated context of a passed-in actor should inherit the execution context of the passed-in actor, but does not.

Steps to reproduce
The following code fails to compile:

func execute<ActorType: Actor>(
    on isolatedActor: isolated ActorType,
    task: @Sendable (isolated ActorType) -> Void)
{
    // Compiler correctly allows this task to execute synchronously.
    task(isolatedActor)
    // Start a task that inherits the current execution context (i.e. that of the isolatedActor)
    Task {
        // BUG: compiler insists that we must `await` the `task`, meaning that this Task is not executing in the isolatedActor's execution context
        task(isolatedActor) // Compiler error: Expression is 'async' but is not marked with 'await'
    }
}

Here's a screenshot of the same code with the inlined compiler error for folk who like Xcode's syntax hilighting:

Expected behavior
I would expect the above code to compile without modification.

Per the Task documentation, a not-detached Task "inherits the priority and actor context of the caller", meaning that a Task created in an isolated ActorType method should execute within the isolated context of the passed-in actor.

Environment

• Swift compiler version info

I was able to reproduce this issue on the following swift compiler versions (I did not try other versions):

swift-driver version: 1.62.15 Apple Swift version 5.7.1 (swiftlang-5.7.1.135.3 clang-1400.0.29.51)
Target: arm64-apple-macosx13.0

swift-driver version: 1.62.15 Apple Swift version 5.7.2 (swiftlang-5.7.2.135.5 clang-1400.0.29.51)
Target: arm64-apple-macosx13.0

• Xcode version info

I was able to reproduce this issue on the following Xcode versions (I did not try other versions):

Xcode 14.1
Build version 14B47b

Xcode 14.2
Build version 14C18

• Deployment target:

.macOS(.v10_15),
.iOS(.v13),
.tvOS(.v13),
.watchOS(.v6),

Additional context

This bug report was first posted as a question in the Swift forums.

Unlike #62503 and #62505, I have not found a way to force the compiler to execute the Task above in the expected execution context.

[ktoso]

Thanks for the report!

Linked to rdar://103337121