[quotes] False positive requiring backticks in types

[BBosman]

Repro

{
  "rules": {
    "quotes": ["error", "backtick", { "avoidEscape": true }]
  }
}

class MockObserver {
  public hasSubscribers: IBindingTargetObserver['hasSubscribers'];
}

Expected Result
No rule violations as those can't be backticks.

Actual Result
Violation of quotes.

Additional Info

Actually changing them to backticks gives a compiler error.

public hasSubscribers: IBindingTargetObserver[`hasSubscribers`];

Error: ']' expected

Versions

package	version
@typescript-eslint/eslint-plugin	1.12.0
@typescript-eslint/parser	1.12.0
TypeScript	3.5.3
ESLint	5.16.0
node	10.15.0
npm	6.10.2

[bradzacher]

See additional request for quotes rule in: #757