const_material_state_property.dart

import 'package:flutter/material.dart';

class _MaterialStatePropertyAll<T> implements MaterialStateProperty<T> {
  const _MaterialStatePropertyAll(this.value);

  final T value;

  @override
  T resolve(Set<MaterialState> states) => value;

  @override
  String toString() => 'MaterialStateProperty.all($value)';
}

void main() {
  print(const _MaterialStatePropertyAll<String>('foo'));
}