Issue Description:

Hi,

I have the following code that throws a compilation error.

Overview

• I have an async let p1 statement

• Then I have 2 statements that await on p1

• Removing one of those 2 awaits removes the error

Compilation error:
Immutable value 'p1' may only be initialized once

Tested on:

• Xcode Version 13.0 beta (13A5155e)

• iOS project that supports only iOS 15.0

• macOS Big Sur (11.4)

Code:

import Foundation

func f1() {
    async {
        async let p1 = computePrice() //Immutable value 'p1' may only be initialized once
        print(await p1)
        let k = await p1
    }
}

func computePrice() async -> Int {
    await withCheckedContinuation { continuation in
        DispatchQueue.main.asyncAfter(deadline: .now() + 4) {
            continuation.resume(returning: 10)
        }
    }
}

It looks like a bug, let me know if I am missing something. Thanks.