anchor.diff:      this.textScaleFactor,
       this.maxLines,
       this.semanticsLabel,
  -  }) : assert(data != null),
  +  }) : assert(
  +         data != null,
  +         'A non-null String must be provided to a Text widget.',
  +       ),
          textSpan = null,
          super(key: key);
   
     /// Creates a text widget with a [TextSpan].
  +  ///
  +  /// The [textSpan] parameter must not be null.
     const Text.rich(this.textSpan, {
       Key key,
       this.style,
  
positive.code:     this.textScaleFactor,
      this.maxLines,
      this.semanticsLabel,
    }) : assert(textSpan != null),
         data = null,
         super(key: key);
  
  
negative.code:   ///
    /// If the [style] argument is null, the text will use the style from the
    /// closest enclosing [DefaultTextStyle].
    ///
    /// The [data] parameter must not be null.
    const Text(this.data, {
      Key key,
      this.style,
  