Add a "Export unused declaration" codefix

🔍 Search Terms

fix unused

✅ Viability Checklist

• 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, new syntax sugar for JS, etc.)
• This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

Add a "Export unused declaration" codefix.

📃 Motivating Example

Before:

function Foo () {

}

After (depends on module type):

export function Foo () {

}

💻 Use Cases

Sometime we may forget to export a declaration and hence the declaration is marked as unused.
To fix it, we have to back to export it manully, which is cumbersome.

Start from the motivating TypeScript example and determine how existing unused-declaration diagnostics and codefixes are implemented. The issue names no files, tests, or entry points, so identify the relevant diagnostic and codefix areas first; done means offering an "Export unused declaration" action that handles the stated module-type distinction without changing runtime behavior.