anchor.diff:    _ExprBuilder(this._context, this._contextElement);
   
     Expression build(kernel.Expression expr) {
  -    try {
  -      return _build(expr);
  -    } on _CompilationErrorFound {
  +    if (_hasInvalidExpression(expr)) {
         return AstTestFactory.identifier3('#invalidConst');
       }
  +    return _build(expr);
     }
   
     ConstructorInitializer buildInitializer(kernel.Initializer k) {
  
positive.code: }
  
  /**
   * This exception is thrown when we detect that the Kernel has a compilation
   * error, so we cannot resynthesize the constant expression.
   */
  class _CompilationErrorFound {
    const _CompilationErrorFound();
  }
  
  /**
   * Builder of [Expression]s from [kernel.Expression]s.
   */
  class _ExprBuilder {
  
negative.code:       }
  
        return AstTestFactory.mapLiteral(keyword, typeArguments, entries);
      }
  
      if (expr is kernel.StaticGet) {
  