anchor.diff:    bool visitExpressionFunctionBody(ast.ExpressionFunctionBody node) {
       if (node.keyword == null) return false;
       return visit(node.expression);
  +  }
  +
  +  bool visitEmptyFunctionBody(ast.EmptyFunctionBody node) {
  +    return false;
  +  }
  +
  +  bool visitFunctionTypeAlias(ast.FunctionTypeAlias node) {
  +    return false;
     }
   
     bool visitArgumentList(ast.ArgumentList node) {
  
positive.code: 
    bool visitClassDeclaration(ast.ClassDeclaration node) {
      node.members.forEach(visit);
      return false;
    }
  
  
negative.code:               AstFactory.propertyAccess2(identifier(result), 'future'))]);
    }
  
    visitExpressionFunctionBody(ast.ExpressionFunctionBody node) {
      if (node.keyword == null) return node;
      return visit(AstFactory.blockFunctionBody2(
          [AstFactory.returnStatement2(node.expression)])
          ..keyword = node.keyword);
    }
  
    visitEmptyFunctionBody(ast.EmptyFunctionBody node) {
      return node;
    }
  
    visitFunctionTypeAlias(ast.FunctionTypeAlias node) {
      return node;
    }
  
    visitCatchClause(ast.CatchClause node) => (f, r, s) {
  