padding: const EdgeInsets.only(
  left: MyMeasurements.globalLeftPadding,right: 20.0,),

我希望能够覆盖“左”.

如果我这样做,我会收到运行时错误：

class MySectionHeader extends StatelessWidget {
    final double left;

MySectionHeader({
  this.left,});

// down to the widget body
padding: const EdgeInsets.only(
  left: left ?? MyMeasurements.globalLeftPadding,// and in the container that has the override...
new MySectionHeader(
  left: 12.0,

这也会出现运行时错误：

padding: const EdgeInsets.only(
  left: left ?? 14.0,

建议？