(edited)

kateinoigakukun

protocol P { typealias Assoc = A } struct A {} struct B: P { typealias Assoc = Int } struct S<T>: P {} extension S where T: P { typealias Assoc = T.Assoc } print(type(of: S<B>.Assoc.self))

Version:

swift-4.2-DEVELOPMENT-SNAPSHOT-2018-05-29-a

Output:

A.Type

Error:

Version:

swift-4.1.1-RELEASE

Output:

A.Type

Error: