[no-unused-vars] False positive on function parameter decorator with default value

[LandazuriPaul]

Reproduction

I noticed that when the @typescript-eslint/no-unused-vars) rule is enabled (either warn or error mode) :

{
  "rules": {
    "@typescript-eslint/no-unused-vars": ["warn"]
  }
}

it triggers a false positive for function parameter decorators when the parameter for which it's used has a default value.

For example, in the following code case:

import { Controller, Get, Query } from '@nestjs/common';
import { AppService } from './app.service';

@Controller()
export class AppController {
  constructor(private readonly appService: AppService) {}

  @Get()
  getHello(@Query('foo') foo = 'bar'): string {
    console.log(foo);
    return this.appService.getHello();
  }
}

the Query decorator will be marked as unused (Line 1). But if we remove the default 'bar' value, then there is no more false positive.

Expected Result

The linter shouldn't raise a warning/error on such circumstances.

Actual Result

The linter raises a warning/error.

Additional Info

I've created a reproduction repository with the above example.

Versions

package	version
@typescript-eslint/eslint-plugin	3.9.0
@typescript-eslint/parser	3.9.0
TypeScript	3.9.7
ESLint	7.6.0
node	12.18.3
npm	6.14.6

[bradzacher]

#1856

Please use the search.

[LandazuriPaul]

@bradzacher Thank you for pointing to the original issue.

I did « use the search », and didn't find it as it's quite meta and didn't appear for what I was looking for...

EDIT: I just found #1649 which has been merged into #1856 and which was the exact same issue. Sorry for the duplicate.