exit status: 1 with stderr:
<stdin>:2:11: error: protocol 'P' can only be used as a generic constraint because it has Self or associated type requirements func f(p: P) {} ^ Using Protocols with 'Self' or Associated Type Requirements Protocols in Swift may be used as types, as part of a generic constraint, or as part of an opaque result type. // CustomStringConvertible can be used as a type. func foo(bar: CustomStringConvertible) { /* ... */ } // ...or as a generic constraint on 'T'. func bar<T: CustomStringConvertible>(baz: T) { /* ... */ } // ...or as part of an opaque result type. func baz() -> some CustomStringConvertible { /* ... */ } While all Swift protocols can be used as generic constraints and as part of opaque result types, not all protocols can be used as types in general. Specifically, if a protocol has a requirement which references 'Self' or an associated type, it cannot be used as a type. One such protocol is 'Identifiable', which has the requirement 'var id: ID { get }', where 'ID' is an associated type. As a result, the following code is not allowed: func foo(bar: Identifiable) { /* ... */ } // error: protocol 'Identifiable' can only be used as a generic constraint because it has Self or associated type requirements Protocols like 'Identifiable' which have 'Self' or associated type requirements cannot be used as types because such types would rarely be useful in practice. They would be unable to allow use of 'Self' or associated type requirements like 'var id: ID { get }' because the associated type is not specified. When working with protocols having 'Self' or associated type requirements constrained generics, opaque result types, or manual type erasure is sufficient to support most use cases. To learn more, see the [Protocols](https://docs.swift.org/swift-book/LanguageGuide/Protocols.html), [Generics](https://docs.swift.org/swift-book/LanguageGuide/Generics.html), and [Opaque Types](https://docs.swif
stderr.txt
https://file.io/paDDGb