Well, that’s strange. I originally thought that this might be tied to playgrounds (which are a bit strange when it comes to scopes) but this reproduces in a command line tool project. You should definitely file a bug about it.
Please post your bug number, just for the record.
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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"