Structure of _StackLayoutCache and related types, used by SwiftUI as the Cache type for VStackLayout and HStackLayout

_StackLayoutCache.swift

// Structure of _StackLayoutCache and related types.
// Used by SwiftUI as the Cache type for VStackLayout and HStackLayout.
//
// As of: iOS 16.0 simulator in Xcode 14.0b6

import SwiftUI

struct _StackLayoutCache {
    var stack: StackLayout
}

struct StackLayout {
    var header: Header
    var children: Array<Child>
    
    struct Header {
        let minorAxisAlignment: AlignmentKey
        let uniformSpacing: Optional<CGFloat>
        let majorAxis: Axis
        var internalSpacing: CGFloat
        var lastProposedSize: ProposedViewSize
        var stackSize: CGSize
        let proxies: LayoutSubviews
        let resizeChildrenWithTrailingOverflow: Bool
    }
    
    struct Child {
        var layoutPriority: Double
        var majorAxisRangeCache: MajorAxisRangeCache
        let distanceToPrevious: CGFloat
        var fittingOrder: Int
        var geometry: ViewGeometry
    }
    
    struct MajorAxisRangeCache {
        var min: Optional<CGFloat>
        var max: Optional<CGFloat>
    }
}

struct AlignmentKey: Hashable /*, Comparable */ {
    let bits: UInt
}

struct ViewGeometry /*: Equatable */ {
    var origin: ViewOrigin
    var dimensions: ViewDimensions
}

struct ViewOrigin: Equatable /*, Animatable */ {
    var value: CGPoint
}

struct ViewDimensions /*: Equatable*/ {
    let guideComputer: LayoutComputer
    var size: ViewSize
}

struct ViewSize: Equatable /*, Animatable */ {
    var value: CGSize
    var _proposal: CGSize
}

struct LayoutComputer /*: Equatable, Defaultable */ {
    var engine: AnyLayoutEngineBox
    var seed: Int
}

class AnyLayoutEngineBox {
    // My reflection code shows no stored properties. Is this true?
}