trying to understand Swift subclass collections

kick.swift

//
//  KickInterpreter.swift
//  Kick
//
//  Created by Bill Tozier on 10/7/21.
//

import Foundation

protocol Pushable {
    associatedtype Item
    var push_type: String { get }
    var value : Item { get }
}

protocol PushItem {
}

// push items

struct PushAtom<T> : PushItem,Pushable {
    var value: T
    var push_type: String
    
    init(_ v: T, _ name: String = "") {
        value = v
        push_type = name
    }
}

struct PushBlock: PushItem,Pushable {
    var value: [PushItem]
    var push_type = "codeblock"

    init(_ v: PushItem ...) {
        value = v
    }
}

struct Foo {
    var bar: String
    
    init(_ bar:String) {self.bar = bar}
}


let b1 = PushAtom<Int64>(11)
let b2 = PushAtom<Double>(2.2)
let b3 = PushAtom<Foo>(Foo("baz"))
let block1 = PushBlock(b1,b2)
let block2 = PushBlock(block1,b3)

print(block.value[0].value)
// ERROR: Value of type 'PushItem' has no member 'value'