使用roslyn，如何获取“var”类型？

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;

string code = @"
using System;

class Program
{
    static void Main()
    {
        var message = ""Hello, world!"";
        Console.WriteLine(message);
    }
}";

SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(code);

var root = syntaxTree.GetRoot();
var varDeclarations = root.DescendantNodes().OfType<VariableDeclarationSyntax>()
                          .Where(v => v.Type.IsVar);

foreach (var varDeclaration in varDeclarations)
{
    var variableType = varDeclaration.Type;
    Console.WriteLine($"Variable type: {variableType}");
}