使用 VS2015 Update 1 编译时表达式破坏代码

Question

在我的机器上安装 Visual Studio 2015 Update 1 后，我发现我的一些单元测试失败了。在做了一些调查之后，我能够将问题减少到这行代码：

Expression<Func<GameObject, bool>> expression = t => t.X == 0 && t.Y == 0 && t.GameObjectType == GameObjectType.WindMill;

将鼠标悬停在表达式变量上时，Visual Studio 版本的结果不同：

对比 2015 年：

VS 2015 更新 1：

对枚举进行比较的逻辑（ServiceStack.OrmLite 代码中的某处）现在的行为有所不同，最终导致枚举未被识别为枚举，从而导致单元测试失败。

我能够使用以下代码重现该问题：

class Program
{
    static void Main(string[] args)
    {
        var gameObjects = new List<GameObject> {
            new GameObject { X = 0, Y = 0, GameObjectType = GameObjectType.WindMill },
            new GameObject { X = 0, Y = 1, GameObjectType = GameObjectType.Pipe },
            new GameObject { X = 0, Y = 2, GameObjectType = GameObjectType.Factory }
        };

        var gameObjectsQueryable = gameObjects.AsQueryable();

        Expression<Func<GameObject, bool>> expression = t => t.X == 0 && t.Y == 0 && t.GameObjectType == GameObjectType.WindMill;

        var result = gameObjectsQueryable.Where(expression);

        var resultAsList = result.ToList();

        foreach (var item in resultAsList)
        {
            Console.WriteLine(item);
        }

        //Obtain the t.GameObjectType == GameObjectType.WindMill part
        var binaryExpression = expression.Body as BinaryExpression;
        var right = binaryExpression.Right;
        var binaryExpression2 = right as BinaryExpression;
        var right2 = binaryExpression2.Right;

        if (right2 is UnaryExpression)
        {
            Console.WriteLine("Found UnaryExpression (This happens when the solution is build with VS2015)...");

            var right2Unary = binaryExpression2.Right as UnaryExpression;
            var right2Constant = right2Unary.Operand as ConstantExpression;
            CheckIfConsantIsAsExpected(right2Constant);
        }
        else
        {
            Console.WriteLine("Found ConstantExpression (This happens when the solution is build with VS2015 Update 1)...");

            var right2Constant = binaryExpression2.Right as ConstantExpression;
            CheckIfConsantIsAsExpected(right2Constant);
        }

        Console.ReadKey();
    }

    public static void CheckIfConsantIsAsExpected(ConstantExpression expression)
    {
        if (expression.Value.Equals(GameObjectType.WindMill))
        {
            Console.WriteLine($"The value is the enum we expected :), : {expression.Value}");
        }
        else
        {
            Console.WriteLine($"The value is not the enum we expected :(, : {expression.Value}");
        }
    }
}

public class GameObject
{
    public int X { get; set; }
    public int Y { get; set; }
    public GameObjectType GameObjectType { get; set; }

    public override string ToString()
    {
        return $"{X},{Y}: {GameObjectType}";
    }
}

public enum GameObjectType
{
    WindMill = 100,
    Pipe = 200,
    Factory = 300
}

在 VS 2015 中它将进入 UnaryExpression 路径，在 VS 2015 Update 1 中它将进入 ConstantExpression 路径。

如果您在 VS 2015 上编译解决方案，然后将编译后的 .exe 文件复制到 VS 2015 Update 1 系统，它将运行与 VS 2015 版本相同（UnaryExpression 路径也是如此）。这表明它与 JIT 无关，而是与构建相关。

我的问题是这是否是故意的？（因为它可能会在简单地重新编译解决方案时破坏现有代码）

Answer 1

这似乎是 RTM VS2015 实际损坏的东西。如果你在没有旧版本 Roslyn 的情况下编译它，它实际上是一个 ConstantExpression。

4.5 编译器：https://dotnetfiddle.net/XpKg10
Roslyn 编译器：https://dotnetfiddle.net/zeGVdh

使用 VS2015 Update 1 编译时表达式破坏代码

Expressions breaking code when compiled using VS2015 Update 1

.net

c#

expression-trees

visual-studio-2015

.net-4.6