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.

Comienza con la reproducción proporcionada en TypeScript Playground y compara su comportamiento con los diagnósticos relacionados 2448 y 2454. Determina si el compilador puede informar de forma sólida que someVar podría no estar inicializada a través de la async closure y, después, valida cualquier diagnóstico con el ejemplo y los casos relacionados existentes.