Invalid Redeclaration of function in Swift - function

Question

I'm trying to write some helper functions and am getting an 'Invalid Redeclaration' error of some similar methods. If anyone can explain why these methods collide I would be very thankful.
func CGRectModify(rect: CGRect, x: CGFloat) -> CGRect {
return CGRectMake(x, rect.origin.y, rect.size.width, rect.size.height)
}
func CGRectModify(rect: CGRect, y: CGFloat) -> CGRect {
return CGRectMake(rect.origin.x, y, rect.size.width, rect.size.height)
}
func CGRectModify(rect: CGRect, width: CGFloat) -> CGRect {
return CGRectMake(rect.origin.x, rect.origin.y, width, rect.size.height)
}
func CGRectModify(rect: CGRect, height: CGFloat) -> CGRect {
return CGRectMake(rect.origin.x, rect.origin.y, rect.size.width, height)
}
I would think that because the second parameter has a different external name, the method would be understood to have a different signature. It seems that is not the case.
I've been using Apple's doc for reference, but in the section of Local and External Parameter Names for Methods I could not find my answer. Any input is much appreciated.

Answer 1

The rule of "automatic external parameter names" for functions are different from methods.
Swift applies different rules depends on the type of callables.
Functions/Closures → document
No "automatic external parameter names" are performed.
func f(x:Int, y:Int) { /* ... */ }
let c = { (x:Int, y:Int) -> Void in /* ... */ }
f(1, 2)
c(1, 2)
Initializers → document
"automatic external parameter names" are the default for every parameters.
class Foo {
init(x:Int, y:Int) { /* ... */ }
}
let foo = Foo(x: 1, y: 2)
Methods → document
"automatic external parameter names" except for the first parameter.
extension Foo {
func bar(x:Int, y:Int) { /* ... */ }
}
foo.bar(1, y:2)
Subscript → document missing?
No "automatic external parameter names" are performed.
extension Foo {
subscript(x:Int, y:Int) -> Void {
get { /* ... */ }
}
}
foo[1, 2]
And a special rule for ...
Default Values
func fz(x:Int, y:Int, z:Int = 1) { /* ... */ }
fz(1, 1, z: 1)
Of course you can override these default behaviors using:
_ name:Type: disable "automatic external parameter names"
#name:Type: force "automatic external parameter names"
externalName internalName:Type: explicit external name

Answer 2

This actually looks like a bug in the documentation. In the section I originally linked to, Local and External Parameter Names for Methods the follow explanation is written.
This default behavior effectively treats the method as if you had written a hash symbol (#) before the numberOfTimes parameter:
func incrementBy(amount: Int, #numberOfTimes: Int) {
count += amount * numberOfTimes
}
This is not the case. When I do add the hash symbol (#) to my second parameter, the compiler error does not occur.
func CGRectModify(rect: CGRect, #height: CGFloat) -> CGRect {
return CGRectMake(rect.origin.x, rect.origin.y, rect.size.width, height)
}