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.

Inizia con la riproduzione fornita in TypeScript Playground e confronta il suo comportamento con le diagnosi correlate 2448 e 2454. Determina se il compilatore può segnalare in modo corretto che someVar potrebbe non essere inizializzata attraverso la async closure, quindi valida qualsiasi diagnostica rispetto all’esempio e ai casi correlati esistenti.