anchor.diff:          IsEnabledByDefault.non_nullable,
           IsExpired.non_nullable,
           'Non Nullable'),
  +    EnableString.control_flow_collections: const ExperimentalFeature(
  +        3,
  +        EnableString.control_flow_collections,
  +        IsEnabledByDefault.control_flow_collections,
  +        IsExpired.control_flow_collections,
  +        'Control Flow Collections'),
  +    EnableString.spread_collections: const ExperimentalFeature(
  +        4,
  +        EnableString.spread_collections,
  +        IsEnabledByDefault.spread_collections,
  +        IsExpired.spread_collections,
  +        'Spread Collections'),
       EnableString.bogus_disabled: const ExperimentalFeature(
           null,
           EnableString.bogus_disabled,
  
positive.code:   /// Expiration status of the experiment "constant-update"
    static const bool constant_update_2018 = false;
  
    /// Expiration status of the experiment "non-nullable"
    static const bool non_nullable = false;
  
    /// Expiration status of the experiment "set-literals"
    static const bool set_literals = false;
  
    /// Expiration status of the experiment "bogus-disabled"
    static const bool bogus_disabled = true;
  
  
negative.code:   /// String to enable the experiment "constant-update"
    static const String constant_update_2018 = 'constant-update-2018';
  
    /// String to enable the experiment "control-flow-collections"
    static const String control_flow_collections = 'control-flow-collections';
  
    /// String to enable the experiment "non-nullable"
    static const String non_nullable = 'non-nullable';
  
    /// String to enable the experiment "set-literals"
    static const String set_literals = 'set-literals';
  
    /// String to enable the experiment "spread-collections"
    static const String spread_collections = 'spread-collections';
  
    /// String to enable the experiment "bogus-disabled"
    static const String bogus_disabled = 'bogus-disabled';
  