Issue Description:

What

A crash happens in the package code when used as a Swift Package Manager dependency.

This only happens only in Xcode 11.2 beta 1 & beta 2. The same code / project works well in Xcode 11.0 and Xcode 11.1. So I believe it is a regression of either Swift compiler or Swift Package Manager (or build system).

It says EXC_BAD_INSTRUCTION but there is no other clue. I have no idea on the reason.

How

Sample repo:

https://github.com/onevcat/Kingfisher-Crash

It is a SwiftUI project, with Kingfisher imported by Swift Package Manager. The ContentView just uses KFImage to load an image from Internet.

Expected

The image loaded and a cat image shown in the middle of the screen.

Actual

The app crashes inside some initializer code in Kingfisher.

Screenshot of the crash:

https://user-images.githubusercontent.com/1019875/66711980-a9d80d80-edd0-11e9-95c8-5d221d0c548c.png

Notes

The same project and integration way works fine on Xcode 11.0 and Xcode 11.1.

With Xcode 11.2 beta / beta 2, the app crashes not only on iOS 13.2 beta, but also crashes on iOS 13.1. So I guess it is more likely a compiler or build system issue?

There is also a related issue reported by Kingfisher community:

onevcat/Kingfisher#1306

Thanks and I appreciate it if you have a chance to look into it! Let me know if you need more information or have any progress on it.