use BindableStore to generate bindings

Samples/SwiftUITestbed/Sources/MainScreen.swift

@@ -31,7 +31,7 @@ extension MainWorkflow.Rendering: SwiftUIScreen, Screen {
 }
 
 private struct MainScreenView: View {
-    var model: Store<MainWorkflow.State>
+    @BindableStore var model: Store<MainWorkflow.State>
 
     @Environment(\.viewEnvironment.marketStylesheet) private var styles: MarketStylesheet
     @Environment(\.viewEnvironment.marketContext) private var context: MarketContext
@@ -49,10 +49,7 @@ private struct MainScreenView: View {
 
             TextField(
                 "Text",
-                text: Binding(
-                    get: { model.title },
-                    set: { _ in fatalError("TODO") }
-                )
+                text: $model.title
             )
             .focused($focusedField, equals: .title)
             .onAppear { focusedField = .title }
@@ -61,10 +58,7 @@ private struct MainScreenView: View {
                 style: context.stylesheets.testbed.toggleRow,
                 label: "All Caps",
                 isEnabled: model.allCapsToggleIsEnabled,
-                isOn: Binding(
-                    get: { model.allCapsToggleIsOn },
-                    set: { _ in fatalError("TODO") }
-                )
+                isOn: $model.allCapsToggleIsOn
             )
 
             Spacer(minLength: styles.spacings.spacing50)

Samples/SwiftUITestbed/Sources/MainWorkflow.swift

@@ -78,7 +78,8 @@ struct MainWorkflow: Workflow {
 
 extension MainWorkflow.State {
     var allCapsToggleIsOn: Bool {
-        isAllCaps
+        get { isAllCaps }
+        set { fatalError("TODO") }
     }
 
     var allCapsToggleIsEnabled: Bool {

Samples/SwiftUITestbed/Sources/Observation/BindableStore.swift

@@ -0,0 +1,38 @@
+// Copied from https://github.com/pointfreeco/swift-composable-architecture/blob/acfbab4290adda4e47026d059db36361958d495c/Sources/ComposableArchitecture/Observation/BindableStore.swift
+
+import ComposableArchitecture
+import SwiftUI
+
+/// A property wrapper type that supports creating bindings to the mutable properties of a
+/// ``Store``.
+///
+/// Use this property wrapper in iOS 16, macOS 13, tvOS 16, watchOS 9, and earlier, when `@Bindable`
+/// is unavailable, to derive bindings to properties of your features.
+///
+/// If you are targeting iOS 17, macOS 14, tvOS 17, watchOS 9, or later, then you can replace
+/// ``BindableStore`` with SwiftUI's `@Bindable`.
+@available(iOS, deprecated: 17, renamed: "Bindable")
+@available(macOS, deprecated: 14, renamed: "Bindable")
+@available(tvOS, deprecated: 17, renamed: "Bindable")
+@available(watchOS, deprecated: 10, renamed: "Bindable")
+@propertyWrapper
+@dynamicMemberLookup
+public struct BindableStore<State: ObservableState> {
+    public var wrappedValue: Store<State>
+    public init(wrappedValue: Store<State>) {
+        self.wrappedValue = wrappedValue
+    }
+
+    public var projectedValue: BindableStore<State> {
+        self
+    }
+
+    public subscript<Subject>(
+        dynamicMember keyPath: ReferenceWritableKeyPath<Store<State>, Subject>
+    ) -> Binding<Subject> {
+        Binding(
+            get: { self.wrappedValue[keyPath: keyPath] },
+            set: { self.wrappedValue[keyPath: keyPath] = $0 }
+        )
+    }
+}

Samples/SwiftUITestbed/Sources/Observation/Store.swift

@@ -36,6 +36,13 @@ public extension Store {
     subscript<T>(dynamicMember keyPath: KeyPath<State, T>) -> T {
         state[keyPath: keyPath]
     }
+
+    subscript<T>(
+        dynamicMember keyPath: WritableKeyPath<State, T>
+    ) -> T {
+        get { state[keyPath: keyPath] }
+        set { state[keyPath: keyPath] = newValue }
+    }
 }
 
 extension Store: Equatable {