Don't suggest converting custom promise-like returning function to async ones

Search Terms

async converted function

Suggestion

Do not suggest that a function is converted to async if its return value is explicitly set to something that is not the global Promise type.

Use Cases

If using a package that provides an extended version of promises (for instance cancellable promises) then the transformation is wrong to occur.

Examples

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.