Array of Nested Type: Why Does the Compiler Complain?

Question

class ClassA {
    class ClassB {
    }
}
let compiles: [ClassA.ClassB]
let doesNotCompile = [ClassA.ClassB]()

Playground execution failed: MyPlayg

Answer 1

As you noted, it works with this syntax:

let arrayOfClassB: [ClassA.ClassB] = []

but the []() syntax works if we declare a typealias:

typealias InnerClass = ClassA.ClassB
let arrayOfAliasesOfClassB = [InnerClass]()

So I'd say it's a bug, let arrayOfClassB = [ClassA.ClassB]() should also work without needing a typealias.

Update: there's already an opened bug about this at Apple.

Answer 2

I don't know the reason why the shorthand syntax does not work. However the compiler seems to like the extended syntax

let list = Array<ClassA.ClassB>()

Answer 3

compiles is an array of type ClassA.ClassB

In doesNotCompile you are trying to use an array as a function. Didn't you mean:

let doesNotCompile = ClassA.ClassB()