Strange compilation error CS0407 even type constraints are specified

[rvhuang]

Not sure if the question is suitable here.
Consider following scenario:

using System; 

namespace ConsoleApp1
{
    class Program
    {
        static T GetInstance<T>()
            where T : IDisposable, new()
        {
            return new T();
        }

        static void DoSomethingOverload1<T>()
            where T : IDisposable, new()
        {
            // Error CS0407
            // 'T Program.GetInstance<T>()' has the wrong return type
            DoSomething(GetInstance<T>);
        }

        static void DoSomethingOverload2<T>()
            where T : IDisposable, new()
        {
            // No error
            DoSomething(() => new T());
        }

        static void DoSomething(Func<IDisposable> factory)  
        {
            // TODO
        }
    }
}

When DoSomethingOverload1() tries to call DoSomething(), the compiler does not consider that GetInstance<T>() has valid return type. However, both DoSomethingOverload1() and GetInstance<T>() explicitly specify that T should implement IDisposable which should fit the signature of DoSomething(). The error does not occur in DoSomethingOverload2().

Thanks for reading the question.

[ufcpp]

        static void DoSomethingOverload1<T>()
            where T : class, IDisposable, new()
        {
            // No error
            DoSomething(GetInstance<T>);
        }

Delegate variance requires a reference type. So you need class constraint.

[ethanae]

@rvhuang, more of a StackOverflow question. Proposal to have this thread closed. Although insightful it doesn't address issues within the language.

[iam3yal]

@rvhuang in addition to what @ethanae said, if you're a bit intimidated by SO or don't use it then you can also create a gist for the code and then ask questions at C# channel, alternatively, join the community that fits your needs, check it out here.