Silver: can't extend Array/Dictionary because can't refer to Element

IDE: Fire
Version: 8.3
Description:

extension Array {
    func foo(x: Element) {
    }
}

Expected Behavior:

Compiles and works correctly.

Actual Behavior:

Error:

error E28: Unknown type "Element"

Steps:

Thanks, logged as bugs://75974

bugs://E18124 was closed as fixed.