SwiftUI – Is there a popViewController equivalent in SwiftUI?

Modify your BView struct as follows. The button will perform just as popViewController did in UIKit.

struct BView: View {
    @Environment(\.presentationMode) var mode: Binding<PresentationMode>
    var body: some View {
        Button(action: { self.mode.wrappedValue.dismiss() })
        { Text("Come back to A") }
    }
}