如何使用FieldTypeDeclaration (Roslyn)更改字段类型

我使用的是visual studio项目类型-独立代码分析工具。我正在使用下面的代码，但是ToString()显示了一个意外的结果。

static void Main(string[] args)
{
    var classDoc = @"public class SomeClass{
            private SomeOtherClass someOtherClass;
        }";
    SyntaxTree classTree=SyntaxFactory.ParseSyntaxTree(classDoc);
    var classDecl = (ClassDeclarationSyntax)classTree.GetRoot().DescendantNodes()
        .First(d => d is ClassDeclarationSyntax);
    var field = classDecl.Members.OfType<FieldDeclarationSyntax>().First();
    var fieldType = field.Declaration.Type;
    var newFieldType = SyntaxFactory.ParseName("System.Windows.Forms.UserControl");
    var newField=field.ReplaceNode(fieldType, newFieldType);
    var newFieldStr = newField.ToString();
}

newFieldStr的值为

private System.Windows.Forms.UserControlsomeOtherClass;

请告知我怎样才能得到预期的结果

var newFieldType = SyntaxFactory.ParseName("System.Windows.Forms.UserControl")
                                .WithTriviaFrom(fieldType);

var newField = field.WithDeclaration(
                    field.Declaration.WithType(
                            SyntaxFactory.ParseName("System.Windows.Forms.UserControl")
                                         .WithTriviaFrom(field.Declaration.Type)));