unused_field

The value of the field '{0}' isn't used.

The analyzer produces this diagnostic when a private field is declared but never read, even if it's written in one or more places.

The following code produces this diagnostic because the field _originalValue isn't read anywhere in the library:

class C {
  final String _originalValue;
  final String _currentValue;

  C(this._originalValue) : _currentValue = _originalValue;

  String get value => _currentValue;
}

It might appear that the field _originalValue is being read in the initializer (_currentValue = _originalValue), but that is actually a reference to the parameter of the same name, not a reference to the field.

If the field isn't needed, then remove it.

If the field was intended to be used, then add the missing code.