protocol P { static func foo() -> Int } extension Never: P { static func foo() -> Int { ??? } } func takeP<T: P>(x: T) -> Int { T.foo() } let x: (any P)? = nil takeP(x) (edited)protocol P { static func foo() -> Int } extension Never: P { static func foo() -> Int { ??? } } func takeP<T: P>(x: T) -> Int { T.foo() } let x: (any P)? = nil takeP(x) (edited)