Your code has an innocuous error and that error is causing the compiler to go off into the weeds, eventually resulting in a very unhelpful diagnostic. Lemme explain the error itself, after which I’ll talk about how I found it.
The error relates to this line:
$0.lowercase
Here $0 is a Substring, and that has no lowercase property. You want the lowercased() method. So, this code compiles:
import Foundation
import RegexBuilder
func main() {
let ampmRef = Reference<String>()
let ampmReg = Regex {
Capture(as: ampmRef) {
ZeroOrMore {
ChoiceOf {
One("am")
One("pm")
}
}
} transform: {
$0.lowercased()
}
}.ignoresCase()
print(ampmReg)
}
main()
Note I had to change the type of ampmRef to match the result of lowercased().
As to how I found this, my experience is when you hit an error like this it’s best to radically simplify your code until you either get things compiling or your get a better error. If you get an error, you can investigate that. OTOH, if it starts to compile without error, you can add stuff back in slowly until things start to fail again.
In your example, I commented out the bulk of what’s inside the Capture and got this error:
import Foundation
import RegexBuilder
func main() {
let ampmRef = Reference<Substring>()
let ampmReg = Regex {
Capture(as: ampmRef) {
// ZeroOrMore {
// ChoiceOf {
One("am")
// One("pm")
// }
// }
} transform: {
$0.lowercase
// ^ Value of type 'Regex<One<String.RegexOutput>.RegexOutput>.RegexOutput' (aka 'Substring') has no member 'lowercase'
}
}.ignoresCase()
print(ampmReg)
}
main()
Clearly the compiler should be better about this, and I encourage you to file a bug about your example.
Please post your bug number, just for the record.
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
