duplicates:

• SR-1486 @available with override causing :0: error

Issue Description:

This simple bit of code:

class MyView: UIView {
    override var insetsLayoutMarginsFromSafeArea: Bool
    {
        didSet { print(insetsLayoutMarginsFromSafeArea) }
    }
}

written in a project whose IPHONEOS_DEPLOYMENT_TARGET is less than 11.0 makes the Swift compiler return <unknown>:0: error: 'insetsLayoutMarginsFromSafeArea' is only available on iOS 11.0 or newer.
Adding an @available(iOS 11, *) decorator to the override doesn't help.

AFAICT, there is no workaround to make the compiler happy.