In response to requests for more clarity. Navigate to your Xcode beta and pop down to Contents/Developer/Platforms. From there go down into any of the Mac platforms, e.g. MacOSX.platform and then to Developer/SDKs and into another platform, e.g. MacOSX10.11.sdk. Next enter System/Library/PrivateFrameworks/Swift.

Your path will look something like this:

/Applications/Xcode\ Beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/PrivateFrameworks/Swift

There you’ll find libswiftCore.tbd. Demangle it:

cat libswiftCore.tbd | /usr/bin/xcrun swift-demangle $1 | open -f

Edit away all the indentations and you end up with something like this.

File feature enhancement requests at bugreport.apple.com. (Power tip: Apple engineers enjoy knock-knock jokes and pictures of kittens in the radar comments section.)