Persistent 'buildExpression unavailable' error in ContentView with switch/AppState

Hi everyone,

I'm encountering a persistent build error in a SwiftUI iOS app and I'm running out of ideas.

Setup: My ContentView uses two @EnvironmentObjects (GameViewModel, SettingsStore). The GameViewModel has an AppState enum (.welcome, .setup, .game). The ContentView body uses a switch viewModel.currentAppState (wrapped in a Group) to display one of three different views (WelcomeView, SetupView, GameView). Navigation between states is triggered by changing viewModel.currentAppState within withAnimation blocks in the respective subviews.

Problem: I consistently get the build error 'buildExpression' is unavailable: this expression does not conform to 'View' pointing to the lines inside the .setup and .game cases of the switch statement in ContentView.

Code (ContentView.swift - Simplified Test Version that STILL fails):

// Zweck: Steuert die Hauptnavigation basierend auf AppState
// KORRIGIERTE VERSION OHNE .animation(...) am Ende

import SwiftUI

struct ContentView: View {
    // Zugriff auf das ViewModel, um den AppState zu lesen
    @EnvironmentObject var viewModel: GameViewModel
    // SettingsStore wird von untergeordneten Views benötigt
    @EnvironmentObject var settingsStore: SettingsStore

    var body: some View {
        // Optional: Group um das switch-Statement, kann manchmal helfen (kannst du auch weglassen)
        Group {
            // Wechsle die Ansicht basierend auf viewModel.currentAppState
            switch viewModel.currentAppState {
            case .welcome:
                WelcomeView()
                    // EnvironmentObjects an WelcomeView übergeben
                    .environmentObject(viewModel)
                    .environmentObject(settingsStore)
                    // Übergangsanimation
                    .transition(.opacity)

            case .setup:
                SetupView()
                    // EnvironmentObjects an SetupView übergeben
                    .environmentObject(viewModel)
                    .environmentObject(settingsStore)
                    // Übergangsanimation
                    .transition(.asymmetric(insertion: .move(edge: .trailing), removal: .move(edge: .leading)))

            case .game:
                GameView()
                    // EnvironmentObjects an GameView übergeben
                    .environmentObject(viewModel)
                    .environmentObject(settingsStore)
                    // Übergangsanimation
                    .transition(.asymmetric(insertion: .move(edge: .trailing), removal: .move(edge: .leading)))
            }
        } // Ende der optionalen Group
        // !!! WICHTIG: KEIN .animation(...) Modifier hier !!!
    }
}

// Vorschau
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        // Erstelle Instanzen für die Vorschau
        let vmWelcome = GameViewModel()
        vmWelcome.currentAppState = .welcome

        let vmSetup = GameViewModel()
        vmSetup.currentAppState = .setup

        let vmGame = GameViewModel()
        vmGame.currentAppState = .game
        vmGame.currentCard = Card.defaultCards.first

        let settings = SettingsStore()

        // Zeige verschiedene Zustände in der Vorschau an
        Group {
            ContentView()
                .environmentObject(vmWelcome)
                .environmentObject(settings)
                .previewDisplayName("Welcome State")

            ContentView()
                .environmentObject(vmSetup)
                .environmentObject(settings)
                .previewDisplayName("Setup State")

            ContentView()
                .environmentObject(vmGame)
                .environmentObject(settings)
                .previewDisplayName("Game State")
        }
    }
}

Troubleshooting Steps Taken (No Success):

• Ensured correct placement of .environmentObject modifiers on subviews within the switch.
• Removed a previous .animation() modifier applied directly to the switch.
• Ensured state changes triggering transitions are wrapped in withAnimation.
• Wrapped the switch in a Group.
• Multiple "Clean Build Folder".
• Deleted entire Derived Data folder (with Xcode closed).
• Restarted Xcode and the Mac multiple times.
• Deleted and recreated ContentView.swift with the code above.
• Crucially: The errors persist even when replacing WelcomeView(), - - - --- SetupView(), and GameView() with simple Text("...") views inside the switch cases (as shown in the code snippet above).

Environment: Xcode Version: newest macOS Version: newest

Question: Does anyone have any idea why the compiler would still fail to type-check this switch structure, even when the views inside are simplified to basic Text? What else could I try to diagnose or fix this? Could it be related to the subviews (SetupView/GameView) potentially having their own NavigationView or complexity, even when replaced by Text in the failing ContentView?

Thanks for any suggestions!