anchor.diff:    final field = zero_;
     const Class9();
   }
  -''', const <ConstantData>[
  +''', constantsCommon: const <ConstantData>[
       const ConstantData(
           'const Class9()', 'ConstructedConstant(Class9(field=IntConstant(0)))'),
     ]),
  
positive.code: class B extends A {
    const B(a) : super(a, a * 2);
  }
  ''', const [
      const ConstantData('const A(c, d)', const <Map<String, String>, String>{
        const {}: 'ConstructedConstant(A(field=IntConstant(15)))',
        const {'foo': '7', 'bar': '11'}:
  
negative.code:   final String declarations;
  
    /// Tested constants.
    final List<ConstantData> constantsCommon;
    final List<ConstantData> constantsPreNnbd;
    final List<ConstantData> constantsNnbdWeak;
    List<ConstantData> get constants =>
        constantsCommon +
        (isDart2jsNnbd && constantsNnbdWeak.isNotEmpty
            ? constantsNnbdWeak
            : constantsPreNnbd);
  
    const TestData(this.name, this.declarations,
        {this.constantsCommon: const [],
        this.constantsPreNnbd: const [],
        this.constantsNnbdWeak: const []});
  }
  
  class ConstantData {
  