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Summary:
I’m defining the cartesian product of two sequences; if these have element types X and Y, then the returned value is a (lazy) sequence of tuple type (X, Y).

I don’t want to expose the implementation details to the consumer of the API; I want them to know that it returns a Sequence whose element type is (X, Y). Therefore, I try to define it thus:

func * <A : Sequence, B : Sequence, C : Sequence where C.GeneratorType.Element == (A.GeneratorType.Element, B.GeneratorType.Element)> (a: A, b: B) -> C {
…
}

However, you can’t relate C’s element type through a tuple—which seems like a bug in its own right.

I’m therefore forced to put implementation details in the return type:



Steps to Reproduce:
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Expected Results:
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Actual Results:
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Regression:
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Notes:
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