Reduce memory usage by Array.Empty

[lindexi]

The Empty property are only used in TypeReferences

[miloush]

Note that this is a public API now returning a fixed array instead of a list, though an array seems more appropriate here.

There is also System.Windows.Markup.Primitives.ElementPropertyBase.EmptyTypes.

[Rand-Random]

The title totally got my expectations high, but the actual code change destroyed my expectations pretty fast.

[vatsan-madhavan]

I was just looking up List yesterday for something else and noticed that new List() seems to have an optimization similar to Array.Empty() in that it returns an empty pre-constructed array by default.

            _items = s_emptyArray;

In situations where an empty List is converted again into an IReadOnlyList etc. that incurs another object allocation, the slight improvement of Array.Empty() is clearer.

        public ReadOnlyCollection<T> AsReadOnly()
            => new ReadOnlyCollection<T>(this);

But straight-up swapping of an empty List with Array.Empty() (esp. for cases where the desired interface type is implemented by either of those, like IEnumerable) - this I'm not sure I understand the benefit of.

[lindexi]

@ vatsan-madhavan Yeah, but we create a static field will cause unnecessary memory allocation, although there is only very little memory.

• a static field
• a List object
  • object meta
  • _items field
  • _size field
  • _version field

[vatsan-madhavan]

Makes sense.