Forgive me if this has already been proposed in one of the generics threads; I
did a quick check and didn’t see anything.
Currently, the code below does not compile:
protocol P {}
struct S: P {}
extension SequenceType where Generator.Element: P {
func foo() {}
}
func F(arr: [P]) {
arr.foo() // error: using 'P' as a concrete type conforming to protocol
'P' is not supported
}
If one changes the where clause in the extension to say Generator.Element == P
instead of : P, the above now works fine, but then the below does not:
protocol P {}
struct S: P {}
extension SequenceType where Generator.Element == P {
func foo() {}
}
func F(arr: [S]) {
arr.foo() // error: 'P' is not convertible to 'S'
}
It seems to me that the first example ought to work; if our constraint is that
Generator.Element conforms to P, something typed as P itself should probably
fit the requirement.
Charles
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