Open Radar

 
Summary:
NSLayout Subclasses use a recursive type description:

```obj-c
@interface NSLayoutYAxisAnchor :
NSLayoutAnchor<NSLayoutYAxisAnchor *>
@end
```

This sort of recursive declaration in swift will just infinitely recurse and hang the compiler.

I'm trying to write a function that will take an axis anchor and return an anchor.  IE:

```swift
func anchorForAxis(axis: NSLayoutYAxisAnchor) -> NSLayoutAnchor<AnyObject> {
    return axis
}
```
This fails with the error:

Cannot convert return expression of type 'NSLayoutYAxisAnchor' to return type 'NSLayoutAnchor<AnyObject>'

This type of failure severely limits the usability of NSLayoutAnchor in swift.

This is being problematic in a library to provide operator overloads:

https://github.com/raizlabs/anchorage

Steps to Reproduce:
Attempt to return an NSLayoutAnchor of an NSLayoutYAxisAnchor. IE:

func anchorForAxis(axis: NSLayoutYAxisAnchor) -> NSLayoutAnchor<AnyObject> {
    return axis
}


Expected Results:
It should work.

Actual Results:
Cannot convert return expression of type 'NSLayoutYAxisAnchor' to return type 'NSLayoutAnchor<AnyObject>'


Version:
Xcode Version 8.0 beta (8S128d)

Notes:


Configuration:
iOS 10