duplicates:

• SR-522 Protocol funcs cannot have covariant returns

Issue Description:

Hello! I think I should be allowed to do this:

protocol P {
    var count: Int? { get }
}

class C: P {
    let count: Int = 5
}

because I can usually assign or pass a T anywhere an Optional<T> is required. But instead I get a compile error:

error: type 'C' does not conform to protocol 'P'
class C: P {
      ^

note: candidate has non-matching type 'Int'
    let count: Int = 5
        ^

This would only be allowed if the protocol specifies a non-settable property. If the protocol requires a setter then a compile error is still appropriate.