Highlight unused symbols #15710
Description
I'd like to request an improvement to Typescript support: highlighting of unused symbols.
Refactoring and moving things around between files often leads to a lot of manual analysis, for example to find imports that are no longer in use.
This doesn't need to be a big, complex feature - I don't expect this to trawl through the entire codebase and figure out what is or isn't in use.
I'd be happy with just file-local highlighting - e.g. gray out variable and constant declarations if they aren't exported or used in any expression or statement anywhere in the file.