Nullable generic not consistant with primitive and object type

[oli-unreal]

C# version: 10

Given this code;

public static void AddNoNullTo<T>(this T? value, List<T> list)
{
    if (value == null) return;
    list.Add(value);
}

It works fine with this code:

public void ShouldNotAddNullValue()
{
    var list = new List<string> { "obj" };
    ((string?)null).AddNoNullTo(list);
    list.ShouldBe(new List<string>{ "obj" });
}

But it doesn't compile when using a primitive type:

public void ShouldNotAddNullValue()
{
    var list = new List<int> { 1 };
    ((int?)null).AddNoNullTo(list);
    list.ShouldBe(new List<int>{ 1 });
}

Error CS0411 : The type arguments for method 'ListExtension.AddNoNullTo(T?, List)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

I was not expecting compilation issue depending of the type of the generic

[HaloFour]

Nullability works differently between reference types and value types (including primitives) and they are not compatible with one another. string? is really just string, but int? is actually Nullable<int>.

[svick]

This also means that you can add an overload of AddNoNullTo specifically for nullable value types:

public static void AddNoNullTo<T>(this T? value, List<T> list)
    where T : struct
{
    if (value == null) return;
    list.Add(value.Value);
}