Detect Typescript in Javascript editors opened and inform developer, that he is writing different syntax and it will silently fail (probably)

It would be super helpful to have something like:

Warning: TypeScript syntax detected in .jsx file. 
Would you like to:
[ ] Rename to .tsx
[ ] Remove TypeScript syntax
[ ] Ignore warning

This kind of UX improvement could save developers (especially those transitioning between JS and TS projects) a lot of time and frustration. It seems like a relatively straightforward detection that could help a lot of people!

VSCode already does similar helpful suggestions for other cases (like offering to create files that don't exist when you import them), so this would fit right in with that philosophy.

What it would solve?

It's the classic .jsx vs .tsx gotcha! 😄

This is such a common issue that even experienced developers run into it regularly. The file extension makes all the difference because:

• .jsx files are treated as regular JavaScript/React files
• .tsx files are treated as TypeScript/React files

So TypeScript typing just "silently fails" to work in .jsx files without any obvious error message about why the types aren't working.

It's one of those "spend an hour debugging only to realize it's a file extension" moments that every developer has experienced!

• .CJS -> .TS, .JS -> .TS, .JSX -> .TSX

(Similar functionality could be created for CSS -> SCSS, ... .)

The issue names no files, tests, or entry points. Start by locating where editor diagnostics or language-service suggestions are implemented, then determine how syntax detection and rename, removal, or ignore actions would fit; done means the proposed warning works for the listed extensions without disrupting valid JavaScript.