EntryTest.swift

import SwiftUI

extension EnvironmentValues {
    @Entry var counter = Binding.constant(0)
    @Entry var inc = {}
}

struct ContentView: View {
    @State private var counter = 0
    
    var body: some View {
        VStack {
            Text("Counter \(counter)")
            ContentView2()
        }
        .font(.title3)
        .buttonStyle(.borderedProminent)        
        .environment(\.counter, $counter)
        .environment(\.inc) {
            counter += 1
        }
    }
}

struct ContentView2: View {
    var body: some View {
        ContentView3()
    }
}

struct ContentView3: View {
    @Environment(\.counter) private var counter
    @Environment(\.inc) private var inc
    
    var body: some View {
        Button("Binding Increment") {
            counter.wrappedValue += 1
        }
        Button("Closure Increment") {
            inc()
        }
    }
}