anchor.diff:          autofocus: autofocus,
           obscureText: obscureText,
           maxLines: maxLines,
  -        onChanged: (String value) {
  -          field.onChanged(value);
  -        },
  +        onChanged: field.onChanged,
         );
       },
     );
  
positive.code: /// pass a [GlobalKey] to the constructor and use [GlobalKey.currentState] to
  /// save or reset the form field.
  ///
  /// See also:
  ///
  ///  * <https://material.google.com/components/text-fields.html>
  
negative.code: ///  * [InputDecorator], which shows the labels and other visual elements that
  ///    surround the actual text editing widget.
  class TextFormField extends FormField<String> {
    /// Creates a [FormField] that contains a [TextField].
    ///
    /// For a documentation about the various parameters, see [TextField].
    TextFormField({
      Key key,
      TextEditingController controller,
  