Comparing a variable of optional enum type with two particular cases in an if statement

I define a Swift enumeration as follows:

enum Direction {
    case up
    case down
    case left
    case right
}

Then I create and initiate a variable of this type:

var direction: Direction = .up

and a variable of the respective optional type:

var optionalDirection: Direction? = .up

Now I want to check against particular cases in the condition of an if statement:

---

1. Compare optional with a single case ✅

if optionalDirection == .up {
    print("Optional direction is 'up'.")
}

prints:

Optional direction is 'up'.

---

2. Compare non-optional with two cases ✅

if direction == .down || direction == .up {
    print("Direction is vertical.")
}

prints:

Direction is vertical.

---

3. Compare optional with two cases ❌

However,

if optionalDirection == .down || optionalDirection == .up {
    print("Optional direction is vertical.")
}

throws an error:

error: invalid character in source file
error: expected '{' after 'if' condition

---

Why does example 3 fail?

Is there a way to fix it without using the rather unintuitive pattern matching syntax (if case ...)?