NullReferenceException with HashSet

[GZTimeWalker]

The code here:

Tomlyn/src/Tomlyn/Model/Accessors/ListDynamicAccessor.cs

Line 154 in c264d1d

_addMethod!.Invoke(list, new[] { value });

will throw a NullReferenceException because of:

Tomlyn/src/Tomlyn/Model/Accessors/ListDynamicAccessor.cs

Lines 45 to 52 in c264d1d

	foreach (var method in type.GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.FlattenHierarchy))
	{
	if (method.Name == "Add" && method.GetParameters().Length == 1 && method.ReturnType == typeof(void) && method.GetParameters()[0].ParameterType == elementType)
	{
	_addMethod = method;
	break;
	}
	}

will never change _addMethod as the declaration of Add method in HashSet is:

bool HashSet<int>.Add(int item);

where the return type is not matched.

---

Maybe add support for ISet or ICollection instead of using a hard-coded method declaration?