Cannot read property 'parent' of undefined when using enums without export

[paolostyle]

Not quite sure if this is the proper package to report an issue but anyway...

What code were you trying to parse?

enum CellType {
  // it's irrelevant what's inside (I think?)
  String = 'string',
  Number = 'number'
}

// some functions later on

What did you expect to happen?
Nothing.

What actually happened?
This kind of error:

TypeError: Cannot read property 'parent' of undefined
Occurred while linting C:\src\src\utils\excelExport.ts:1
    at variable.defs.some.def (C:\src\node_modules\eslint\lib\rules\no-unused-vars.js:184:54)
    at Array.some (<anonymous>)
    at hasRestSpreadSibling (C:\src\node_modules\eslint\lib\rules\no-unused-vars.js:182:38)
    at collectUnusedVariables (C:\src\node_modules\eslint\lib\rules\no-unused-vars.js:578:80)
    at collectUnusedVariables (C:\src\node_modules\eslint\lib\rules\no-unused-vars.js:585:17)
    at Program:exit (C:\src\node_modules\eslint\lib\rules\no-unused-vars.js:630:36)
    at listeners.(anonymous function).forEach.listener (C:\src\node_modules\eslint\lib\util\safe-emitter.js:45:58)
    at Array.forEach (<anonymous>)
    at Object.emit (C:\src\node_modules\eslint\lib\util\safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (C:\src\node_modules\eslint\lib\util\node-event-generator.js:251:26)
Process finished with exit code -1

Everything is okay if I use export enum CellType. I'm extending recommended config so no-unused-vars from eslint should be disabled.

{
'@typescript-eslint/no-unused-vars': [
      'error',
      {
        vars: 'all',
        args: 'after-used',
        ignoreRestSiblings: true
      }
    ]
}

Versions

package	version
@typescript-eslint/parser	1.5.0
TypeScript	3.3.3333
ESLint	5.15.3
node	10.13.0
npm	6.4.1