[no-unused-vars] False positive with parameter decorators with default values

[robin-pham]

Repro

{
  "rules": {
    "@typescript-eslint/no-unused-vars": [
      "error",
      {
        "vars": "all",
        "args": "none"
      }
    ]
  }
}

const log = function(target: Object, method: string, index: number): void {
  console.log('decorating %s[%d]', method, index);
};

class Test {
  public sum(a: number, @log b: number = 7): number {
    return a + b;
  }
}

Expected Result

No violation of unused-vars is reported.

Actual Result

It complains that log is assigned a value but never used.

Additional Info

Note: the rule works fine if there is no default value.

Versions
Tried on two sets of versions:

package	version
@typescript-eslint/eslint-plugin	2.21.0
@typescript-eslint/parser	2.21.0
TypeScript	3.3.3333
ESLint	6.8.0
node	12.14.1
npm	6.13.4

and

package	version
@typescript-eslint/eslint-plugin	1.4.2
@typescript-eslint/parser	1.4.2
TypeScript	3.3.3333
ESLint	5.15.1
node	12.14.1
npm	6.13.4

[bradzacher]

please try switching to our no-unused-vars-experimental rule, it will work in this case.

[robin-pham]

gotcha, tried it out and it works!

sadly though our codebase uses options in no-unused-vars that don't exist in no-unused-vars-experimental :(.

thanks for the quick reply!

[bradzacher]

Options like what?
Potentially could be built into the new rule.

[bradzacher]

Merging into #1856