Compiler error when comparing values of enum type?

class MyClass 
{
    enum MyEnum {
        case FirstCase
        case SecondCase
        case ThirdCase
    }

    var state:MyEnum!

    func myMethod ()
    {
        if state! == MyEnum.FirstCase {
            // Do something
        }
    }
}

I get the compiler error pointing at the if statement::

Binary operator '==' cannot be applied to two 'MyClass.MyEnum' operands

If instead, I use a switch statement, there is no problem:

switch state! {
    // Also, why do I need `!` if state is already an 
    // implicitly unwrapped optional? Is it because optionals also 
    // are internally enums, and the compiler gets confused?

case .FirstCase:
    // do something...

default:
    // (do nothing)
    break
}

However, the switch statement feels too verbose: I just want to do something for .FirstCase, and nothing otherwise. An if statement makes more sense.

What's going on with enums and == ?