[Feature] allow use `xxx is Type` with async function

Search Terms

Suggestion

Use Cases

Examples

export async function checkIPFS(ipfs): awaited ipfs is IIPFSPromiseApi
{
return true
}

if (await checkIPFS(ipfs))
{
// here will know ipfs is IIPFSPromiseApi
}

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Commencez par l’exemple TypeScript de l’issue et comparez le comportement demandé des type predicates asynchrones avec le comportement actuel du compilateur. Consultez les TypeScript design goals liés avant de décider si la syntaxe et le control-flow narrowing sont viables ; le travail est considéré comme terminé lorsque la proposition possède un comportement défini et accepté, ainsi que des tests couvrant l’exemple.