gistfile1.swift

import Cocoa

class GeneralThing<S> {
	var stuff: S?

	func doIt() {
		if let s = stuff {
			doWithStuff(s)
		}
	}

	func doWithStuff(stuff: S) -> S {
		return stuff
	}
}

class SpecificThing<T>: GeneralThing<Int> {
	override func doWithStuff(stuff: Int) -> Int {
		println("\(stuff + 1)")
		return stuff + 1
	}
}

let t = SpecificThing<Int>()
t.stuff = 1
t.doIt()

Line 18:

Execution was interrupted, reason: EXC_BAD_ACCESS

This still an issue in Swift 2.0?

Checked that in swift 2.0 playground, all works as excpected