anchor.diff:  
     _UiKitApplePayButton({
       Key? key,
  -    required this.onPressed,
  +    this.onPressed,
       this.style = ApplePayButtonStyle.black,
       this.type = ApplePayButtonType.plain,
     }) : super(key: key);
  
positive.code: part of '../../pay_ios.dart';
  
  const double _defaultButtonHeight = 48.0;
  
  enum ApplePayButtonType {
    plain,
  
negative.code:   automatic,
  }
  
  extension _ApplePayButtonTypeAsset on ApplePayButtonType {
    double get minimumAssetWidth => this == ApplePayButtonType.plain ? 100 : 140;
  }
  
  class RawApplePayButton extends StatelessWidget {
    static const double _minimumButtonHeight = 30;
  
    final BoxConstraints constraints;
    final EdgeInsets margin;
    final VoidCallback? onPressed;
    final ApplePayButtonStyle style;
    final ApplePayButtonType type;
  
    RawApplePayButton({
      Key? key,
      this.onPressed,
      this.margin = EdgeInsets.zero,
      this.style = ApplePayButtonStyle.black,
      this.type = ApplePayButtonType.plain,
    })  : constraints = BoxConstraints.tightFor(
            width: type.minimumAssetWidth,
            height: _minimumButtonHeight,
          ),
          super(key: key) {
      assert(constraints.debugAssertIsValid());
    }
  