Optimize Example project

Example/HostingExample/ViewController.swift

@@ -14,13 +14,61 @@ import SwiftUI
 
 class ViewController: UINavigationController {
     override func viewDidAppear(_ animated: Bool) {
-        let vc = UIHostingController(rootView: ContentView())
-        pushViewController(vc, animated: false)
+        pushViewController(EntryViewController(), animated: false)
     }
 }
 
+final class EntryViewController: UIViewController {
+    override func viewDidLoad() {
+        navigationItem.rightBarButtonItem = UIBarButtonItem(
+            title: "Push",
+            style: .plain,
+            target: self,
+            action: #selector(pushHostingVC)
+        )
+        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+            self.pushHostingVC()
+        }
+    }
+
+    @objc
+    private func pushHostingVC() {
+        guard let navigationController else { return }
+        let hostingVC = UIHostingController(rootView: ContentView())
+        navigationController.pushViewController(hostingVC, animated: true)
+    }
+}
+
+// TODO: Known issue
+// 1. State toggle crash
+// 2. pop - UIHostingView deinit crash / onDisappear
+// 3. if else builder issue
 struct ContentView: View {
+    @State private var first = true
+
     var body: some View {
-        AnyView(EmptyView())
+        if first {
+            Color.red
+                .onAppear {
+                    print("Red appear")
+                    DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+                        first.toggle()
+                    }
+                }
+                .onDisappear {
+                    print("Red disappear")
+                }
+        } else {
+            Color.blue
+                .onAppear {
+                    print("Blue appear")
+                    DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+                        first.toggle()
+                    }
+                }
+                .onDisappear {
+                    print("Blue disappear")
+                }
+        }
     }
 }

Sources/OpenSwiftUI/Core/Modifier/SceneModifier/TODO/_SceneModifier.swift

@@ -22,6 +22,6 @@ extension _SceneModifier {
 extension _SceneModifier where Body == Never {
     @inline(__always)
     public func body(content _: SceneContent) -> Body {
-        preconditionFailure("body() should not be called on \(Self.self)")
+        preconditionFailure("body() should not be called on \(Self.self).")
     }
 }

Sources/OpenSwiftUI/Scene/Core/Scene.swift

@@ -16,6 +16,6 @@ extension Never: Scene {}
 
 extension Scene {
     func sceneBodyError() -> Never {
-        preconditionFailure("body() should not be called on \(Self.self)")
+        preconditionFailure("body() should not be called on \(Self.self).")
     }
 }

Sources/OpenSwiftUICore/Graphic/Color/ColorView.swift

@@ -3,17 +3,39 @@
 //  OpenSwiftUICore
 //
 //  Audited for iOS 18.0
-//  Empty
+//  Status: Empty
 
-@MainActor
-@preconcurrency
-package struct ColorView: PrimitiveView { //FIXME
+package import Foundation
+
+package struct ColorView: RendererLeafView, Animatable {
     package var color: Color.Resolved
 
     package init(_ color: Color.Resolved) {
         self.color = color
     }
 
-    @available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
-    package typealias Body = Swift.Never
+    nonisolated package static func _makeView(view: _GraphValue<ColorView>, inputs: _ViewInputs) -> _ViewOutputs {
+        var inputs = inputs
+        if inputs.base.options.isEmpty {
+            // TODO: AnimatableAttribute
+        }
+        return makeLeafView(view: view, inputs: inputs)
+    }
+
+    package var descriptionAttributes: [(name: String, value: String)] {
+        preconditionFailure("TODO")
+    }
+
+    package func contains(points: [PlatformPoint], size: CGSize) -> BitVector64 {
+        preconditionFailure("TODO")
+    }
+
+    package func content() -> DisplayList.Content.Value {
+        preconditionFailure("TODO")
+    }
+
+    package var animatableData: Color.Resolved.AnimatableData {
+        get { color.animatableData  }
+        set { color.animatableData = newValue }
+    }
 }

Sources/OpenSwiftUICore/Modifier/ViewModifier/ViewModifier.swift

@@ -137,7 +137,7 @@ extension ViewModifier where Self: _GraphInputsModifier, Body == Never {
 
 extension ViewModifier {
     func bodyError() -> Never {
-        preconditionFailure("body() should not be called on \(Self.self)")
+        preconditionFailure("body() should not be called on \(Self.self).")
     }
 }
 

Sources/OpenSwiftUICore/Render/RendererLeafView.swift

@@ -0,0 +1,28 @@
+//
+//  RendererLeafView.swift
+//  OpenSwiftUICore
+//
+//  Audited for iOS 18.0
+//  Status: WIP
+
+import Foundation
+
+package protocol RendererLeafView: /*ContentResponder,*/ PrimitiveView, UnaryView {
+    static var requiresMainThread: Bool { get }
+    func content() -> DisplayList.Content.Value
+}
+
+extension RendererLeafView {
+    package static var requiresMainThread: Swift.Bool {
+        false
+    }
+
+    func contains(points: [PlatformPoint], size: CGSize) -> BitVector64 {
+        preconditionFailure("TODO")
+    }
+
+    package static func makeLeafView(view: _GraphValue<Self>, inputs: _ViewInputs) -> _ViewOutputs {
+        // preconditionFailure("TODO")
+        _ViewOutputs()
+    }
+}

Sources/OpenSwiftUICore/View/View.swift

@@ -106,7 +106,7 @@ extension PrimitiveView {
 
 extension View {
     package func bodyError() -> Never {
-        preconditionFailure("body() should not be called on \(Self.self)")
+        preconditionFailure("body() should not be called on \(Self.self).")
     }
 }
 

Sources/OpenSwiftUICore/View/ViewBuilder.swift

@@ -1,16 +1,23 @@
 //
 //  ViewBuilder.swift
-//  OpenSwiftUI
+//  OpenSwiftUICore
 //
-//  Audited for RELEASE_2023
+//  Audited for iOS 18.0
 //  Status: Complete
 
 @resultBuilder
-public enum ViewBuilder {
+public struct ViewBuilder {
     @_alwaysEmitIntoClient
     public static func buildExpression<Content>(_ content: Content) -> Content where Content: View {
         content
     }
+
+    @available(*, unavailable, message: "this expression does not conform to 'View'")
+    @_disfavoredOverload
+    @_alwaysEmitIntoClient
+    public static func buildExpression(_ invalid: Any) -> some View {
+        fatalError()
+    }
 
     @_alwaysEmitIntoClient
     public static func buildBlock() -> EmptyView {
@@ -30,7 +37,7 @@ public enum ViewBuilder {
 }
 
 @available(*, unavailable)
-extension ViewBuilder: Swift.Sendable {}
+extension ViewBuilder: Sendable {}
 
 extension ViewBuilder {
     @_alwaysEmitIntoClient