[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.

从 issue 中的 TypeScript 示例开始，将其请求的 async type-predicate 行为与当前 compiler 的行为进行比较。在决定该语法和 control-flow narrowing 是否可行之前，先查看链接的 TypeScript design goals；完成的标准是 proposal 具有明确且已接受的行为，并且有覆盖该示例的 tests。