Kill compiler with this one weird trick

File.swift

import UIKit

class ViewController: UIViewController {

  private var a1: Int!
  private var a2: Int!
  private var a3: Int!
  private var a4: Int!
  private var a5: Int!
  private var a6: Int!
  private var a7: Int!
  private var a8: Int!
  private var a9: Int!
  private var a10: Int!
  private var a11: Int!
  private var a12: Int!
  private var a13: Int!
  private var a14: Int!
  private var a15: Int!

  private var aas: [Int?] {
    return [
      a1,
      a2,
      a3,
      a4,
      a5,
      a6,
      a7,
// Uncommenting these results in indefinite compilation
//      a8,
//      a9,
//      a10,
//      a11,
//      a12,
//      a13,
//      a14,
//      a15,
    ]
  }
}