TypeScript doesn't error on late definition/initialization of variables from outside an async closure.

TypeScript Version: 4.0-beta and Nightly (as of writing)

Search Terms: async closure variable initialization

Code

async function doSomething(): Promise<void> {
    const x = setTimeout(() => {
        const a = someVar + 1;
    }, 5000)

    await doSomethingSlowly();

    const someVar = 5;
}

Expected behavior:
There should be an error on const a = someVar + 1; since someVar may not have been initialized.

Actual behavior:
No error/warning with any settings that I could find.

Playground Link: link

Related Issues:

Comments
I see folks hit this every so often and it feels like something the TypeScript compiler could help warn against, in a similar way that 2448 and 2454 error.

提供された TypeScript Playground の再現例から始め、関連する診断 2448 および 2454 と動作を比較してください。async closure をまたいで someVar が未初期化である可能性をコンパイラーが健全に報告できるかどうかを判断し、その後、例および既存の関連ケースに照らして診断を検証してください。