anchor.diff:  }
   
   class TypeTests {
  -  TypeTest isTest;
  -  TypeTest substitution;
  -  TypeTest signature;
  +  TypeTest? isTest;
  +  TypeTest? substitution;
  +  TypeTest? signature;
   }
   
   class TypeTestProperties {
  
positive.code:   /// If the is tests were generated with `storeFunctionTypeInMetadata` set to
    /// `false`, this field is `null`, and the [properties] contain a property
    /// that encodes the function type.
    jsAst.Expression functionTypeIndex;
  
    /// The properties that must be installed on the prototype of the
    /// JS constructor of the [ClassEntity] for which the is checks were
  
negative.code: // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
  // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  library dart2js.js_emitter.runtime_type_generator;
  
  