Created
September 19, 2011 16:44
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No Nothings
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| def unexpected : Nothing = sys.error("Unexpected invocation") | |
| // Encoding for "A is not a subtype of B" | |
| trait <:!<[A, B] | |
| // Uses ambiguity to rule out the cases we're trying to exclude | |
| implicit def nsub[A, B] : A <:!< B = null | |
| implicit def nsubAmbig1[A, B >: A] : A <:!< B = unexpected | |
| implicit def nsubAmbig2[A, B >: A] : A <:!< B = unexpected | |
| // Type alias for context bound | |
| type |¬|[T] = { | |
| type λ[U] = U <:!< T | |
| } | |
| def something[T: |¬|[Nothing]#λ](t : T) = t | |
| val smth1 = something(23) // OK | |
| val smth2 = something("foo") // OK | |
| val smth3 = something(error("Boom!")) // Does not compile |
wow... I didn't think it was possible...
Nice.
It looks like you can replace with |¬| with just ¬. Any particular reason for the bars?
implicit def nsubAmbig1[A, B >: A] : A <:!< B = unexpected
implicit def nsubAmbig2[A, B >: A] : A <:!< B = unexpected
why this duplication?
@epiphyllum because otherwise, this trick doesn't work 😄
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why exactly is this not in the standard library?