Swift Generics: Cannot convert value of type to expected argument type

Here is my code:

protocol SomeProtocol {
}

class A: SomeProtocol {
}

func f1<T: SomeProtocol>(ofType: T.Type, listener: (T?) -> Void) {
}

func f2<T: SomeProtocol>(ofType: T.Type, listener: ([T]?) -> Void) {
}

func g() {
    let l1: (SomeProtocol?) -> Void = ...
    let l2: ([SomeProtocol]?) -> Void = ...
    f1(ofType: A.self, listener: l1) // NO ERROR
    f2(ofType: A.self, listener: l2) // COMPILE ERROR: Cannot convert value of type '([SomeProtocol]?) -> Void' to expected argument type '([_]?) -> Void'
}

What is the problem with the second closure having an argument of an array of generic type objects?