DiagnosticsNode constructor
- required String? name,
 - DiagnosticsTreeStyle? style,
 - bool showName = true,
 - bool showSeparator = true,
 - String? linePrefix,
 
Initializes the object.
The style, showName, and showSeparator arguments must not
be null.
Implementation
DiagnosticsNode({
  required this.name,
  this.style,
  this.showName = true,
  this.showSeparator = true,
  this.linePrefix,
}) : assert(
       // A name ending with ':' indicates that the user forgot that the ':' will
       // be automatically added for them when generating descriptions of the
       // property.
       name == null || !name.endsWith(':'),
       'Names of diagnostic nodes must not end with colons.\n'
       'name:\n'
       '  "$name"',
     );