Borders not covering background - swift

Question

I've got a UILabel is using a border the same color as a background which it is half obscuring, to create a nice visual effect. However the problem is that there is still a tiny, yet noticeable, sliver of the label's background color on the OUTSIDE of the border.
The border is not covering the whole label!
Changing the border width doesn't change anything either, sadly.
Here's a picture of what's going on, enlarged so you can see it:
And my code follows:
iconLbl.frame = CGRectMake(theWidth/2-20, bottomView.frame.minY-20, 40, 40)
iconLbl.font = UIFont.fontAwesomeOfSize(23)
iconLbl.text = String.fontAwesomeIconWithName(.Info)
iconLbl.layer.masksToBounds = true
iconLbl.layer.cornerRadius = iconLbl.frame.size.width/2
iconLbl.layer.borderWidth = 5
iconLbl.layer.borderColor = topBackgroundColor.CGColor
iconLbl.backgroundColor = UIColor.cyanColor()
iconLbl.textColor = UIColor.whiteColor()
Is there something I'm missing?
Or am I going to have to figure out another to achieve this effect?
Thanks!
EDIT:
List of things I've tried so far!
Changing layer.borderWidth
Fussing around with clipsToBounds/MasksToBounds
Playing around the the layer.frame
Playing around with an integral frame
EDIT 2:
No fix was found! I used a workaround by extending this method on to my UIViewController
func makeFakeBorder(inputView:UIView,width:CGFloat,color:UIColor) -> UIView {
let fakeBorder = UIView()
fakeBorder.frame = CGRectMake(inputView.frame.origin.x-width, inputView.frame.origin.y-width, inputView.frame.size.width+width*2, inputView.frame.size.height+width*2)
fakeBorder.backgroundColor = color
fakeBorder.clipsToBounds = true
fakeBorder.layer.cornerRadius = fakeBorder.frame.size.width/2
fakeBorder.addSubview(inputView)
inputView.center = CGPointMake(fakeBorder.frame.size.width/2, fakeBorder.frame.size.height/2)
return fakeBorder
}

Answer 1

I believe this is the way a border is drawn to a layer in iOS. In the document it says:
When this value is greater than 0.0, the layer draws a border using the current borderColor value. The border is drawn inset from the receiver’s bounds by the value specified in this property. It is composited above the receiver’s contents and sublayers and includes the effects of the cornerRadius property.
One way to fix this is to apply a mask to a view's layer, but I found out that even if so we still can see a teeny tiny line around the view when doing snapshot tests. So to fix it more, I put this code to layoutSubviews
class MyView: UIView {
override func layoutSubviews() {
super.layoutSubviews()
let maskInset: CGFloat = 1
// Extends the layer's frame.
layer.frame = layer.frame.inset(dx: -maskInset, dy: -maskInset)
// Increase the border width
layer.borderWidth = layer.borderWidth + maskInset
layer.cornerRadius = bounds.height / 2
layer.maskToBounds = true
// Create a circle shape layer with true bounds.
let mask = CAShapeLayer()
mask.path = UIBezierPath(ovalIn: bounds.inset(dx: maskInset, dy: maskInset)).cgPath
layer.mask = mask
}
}
CALayer's mask