How to get CGContext's Error in Swift

I'm trying to convert an CGImage to MTLTexture, and for this, I'm using this code:

let width = cgimage.width
let height = cgimage.height
let channels = cgimage.bitsPerPixel / cgimage.bitsPerComponent


let colorSpace = cgimage.colorSpace!


let bitsPerComponent = cgimage.bitsPerComponent


let bytesPerComponent = cgimage.bitsPerComponent / 8
let bytesPerPixel = cgimage.bitsPerPixel / 8


let bytesPerRow = width * bytesPerPixel
let options = CGImageAlphaInfo.premultipliedLast.rawValue


var pixelValues = [UInt8](repeating: 0, count: width * height * channels)


let contextRef = CGContext(data: &pixelValues, width: width, height: height,
                        bitsPerComponent: bitsPerComponent,
                        bytesPerRow: bytesPerRow,
                        space: colorSpace, bitmapInfo: options)


contextRef?.draw(cgimage, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(width), height: CGFloat(height)))

My problem is that CGContext is extremely finicky, and it just returns nil without any explanation if some of it's obscure options are not perfectly set, for example in bitmapInfo.

Now, I've seen some tutorials online in ObjC where it was using CGContextRef which provided errors with nice, detailed explanation.

However in Swift, it's just an empty nil, without any warning lines or anything. This is just extremely hard to develop anything like this, I'm pretty much just guessing in the dark.

For example, I'm trying to figure out, why does this function work with

UInt8

UInt16

Float