为什么Func/Lambdas通过返回类型解析方法重载,而方法不解决？

Question

我已经定义了这些方法重载,只有Action/Func参数不同:

    public void DoSomethingWithValues(Action<decimal, decimal> d, decimal x, decimal y)
    {
        d(x, y);
    }

    public void DoSomethingWithValues(Func<decimal, decimal, decimal> d, decimal x, decimal y)
    {
        var value = d(x, y);
    }

我尝试通过内联lambda,Func <>和方法调用它们:

    public Func<decimal, decimal, decimal> ImAFuncWhichDoesSomething = (x, y) => (x + y) / 5;

    public decimal ImAMethodWhichDoesSomething(decimal x, decimal y)
    {
        return (x + y + 17) / 12;
    }

    public void DoSomething()
    {
        DoSomethingWithValues((x, y) => (x - y) / 17 , 1, 2);       // Inline lambda compiles OK
        DoSomethingWithValues(ImAFuncWhichDoesSomething, 1, 2);     // Func<> compiles OK
        DoSomethingWithValues(ImAMethodWhichDoesSomething, 1, 2);   // Method generates "ambiguous invocation" error!!
    }

前两个编译正常并通过返回类型解析.

但是由于"模糊调用"错误,方法无法编译!

为什么lambda/func通过返回类型解决重载,而方法不解决？