[swift-evolution] extending typealiases

Adrian Zubarev adrian.zubarev at devandartist.com
Mon Feb 6 12:12:46 CST 2017

Okay fine. I’m curious if we ever should be able to extend existentials. (Could be really handy.)

typealias FooView = UIView & Foo

extension FooView {
     func foo() { .. }

// vs.
extension UIView where Self : Foo { .. }

Adrian Zubarev
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Am 6. Februar 2017 um 19:06:16, Anton Zhilin (antonyzhilin at gmail.com) schrieb:

If I understand correctly, extension of a typealias should be strictly equivalent to extension of type on the right:

extension Any<class> {
    func foo()
Any<...> are not nominal types, so until we additionally allow extensions for non-nominal types, this will not compile.

2017-02-06 20:51 GMT+03:00 Adrian Zubarev via swift-evolution <swift-evolution at swift.org>:

Just imagining the future. Iff this request will made into the language and we had typealias AnyObject = Any<class>, would the following be valid?

extension AnyObject {
    func foo()
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