Why is lambda without closures turned into an instance method rather than a static one?

[voroninp]

While playing with this code:

var wr = new WeakReference(() => 1);
GC.Collect(2, GCCollectionMode.Aggressive, blocking: true, compacting: true);
GC.WaitForPendingFinalizers();
Console.WriteLine(wr.IsAlive);

I've discovered it looks like this one:

WeakReference weakReference = new WeakReference(<>c.<>9__4_0 ?? (<>c.<>9__4_0 = <>c.<>9.<Main>b__4_0));
GC.Collect(2, GCCollectionMode.Aggressive, true, true);
GC.WaitForPendingFinalizers();
Console.WriteLine(weakReference.IsAlive);

plus:

[Serializable]
[CompilerGenerated]
private sealed class <>c
{
	public static readonly <>c <>9 = new <>c();

	public static Func<int> <>9__4_0;

	internal int <Main>b__4_0()
	{
		return 1;
	}
}

But why is <Main>b__4_0 method not static?

If I replace lambda with (Action)Console.WriteLine, then I get this code:

WeakReference weakReference = new WeakReference(<>O.<0>__WriteLine ?? (<>O.<0>__WriteLine = Console.WriteLine));
GC.Collect(2, GCCollectionMode.Aggressive, true, true);
GC.WaitForPendingFinalizers();
Console.WriteLine(weakReference.IsAlive);

plus:

[CompilerGenerated]
private static class <>O
{
	public static Action <0>__WriteLine;
}

[CyrusNajmabadi]

Instance method invocation in a delegate is faster. It's a detail of the runtime that we exploit for performance.

[voroninp]

Wow.

[KennethHoff]

Do you have a use-case in mind that cares for whether it's actually static or not, or were you simply wondering?

[voroninp]

Simply curious