Hi Slava, Thank you very much for the quick response. As you requested, I filed the bug under the following link: https://bugs.swift.org/browse/SR-6561
Best Regards Mario From: <spes...@apple.com> on behalf of Slava Pestov <spes...@apple.com> Date: Thursday, 7 December 2017 at 22:27 To: Mario Meili <mario.me...@live.com> Cc: "swift-users@swift.org" <swift-users@swift.org> Subject: Re: [swift-users] Multiple Class Types in Protocol Composition Hi Mario, You’re right that this part of the proposal was not fully implemented. Computing the common ancestor of two superclasses is a little tricky here because it would force us to resolve the superclass type of a class when realizing a subclass existential. This would introduce circular dependencies. Either I missed something obvious or it would require some re-architecting of the type checker to make it work. Either way, yes it’s a known limitation, but not one that is tracked by a JIRA presently, so please do file a bug! Thanks, Slava On Dec 7, 2017, at 7:17 AM, Mario Meili via swift-users <swift-users@swift.org<mailto:swift-users@swift.org>> wrote: Hi everyone, I noticed strange behaviour of the Swift 4.0.3 compiler regarding class and subtype existentials. According to the proposal SE-0156 (https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fapple%2Fswift-evolution%2Fblob%2Fmaster%2Fproposals%2F0156-subclass-existentials.md&data=02%7C01%7C%7Cf12145f448334d2a644c08d53db941d1%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636482788230444913&sdata=bjKRAVds%2BubJz5Mpi27bQmpbBigAfekf%2FiXopHekabE%3D&reserved=0>), multiple class types in protocol compositions should be allowed, if: * The class types are the same * Or, one class type must be a subtype of the other. However, when copying the exact code from the proposal into Xcode 9.2, the result is the following: <image001.png> My conclusion here is that the compiler does not allow multiple class types in one protocol composition. My question is: Is this behaviour intended or should I open a bug report? Thank you very much BR Mario _______________________________________________ swift-users mailing list swift-users@swift.org<mailto:swift-users@swift.org> https://lists.swift.org/mailman/listinfo/swift-users<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.swift.org%2Fmailman%2Flistinfo%2Fswift-users&data=02%7C01%7C%7Cf12145f448334d2a644c08d53db941d1%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636482788230444913&sdata=pY7NkpjW9jmvnhjXYa3axI%2F631OaDOdJ0F4KsIb%2FXHI%3D&reserved=0>
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