ListEnumeratorAllocation.cs

using System.Collections;
using System.Collections.Generic;
					
public class Program
{
	public static void Main()
	{
        // Will allocate.
		IList list =  new List<int>();
		foreach (var item in list)
		{
		}
        
        // Will not allocate.
        List<int> list2 = new List<int>();
        foreach (var item in list2)
		{
		}
	}
}

​ListEnumeratorAllocation.decompiled.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Security;
using System.Security.Permissions;
using Microsoft.CodeAnalysis;

[assembly: CompilationRelaxations(8)]
[assembly: RuntimeCompatibility(WrapNonExceptionThrows = true)]
[assembly: Debuggable(DebuggableAttribute.DebuggingModes.Default | DebuggableAttribute.DebuggingModes.IgnoreSymbolStoreSequencePoints | DebuggableAttribute.DebuggingModes.EnableEditAndContinue | DebuggableAttribute.DebuggingModes.DisableOptimizations)]
[assembly: SecurityPermission(SecurityAction.RequestMinimum, SkipVerification = true)]
[assembly: AssemblyVersion("0.0.0.0")]
[module: UnverifiableCode]
[module: System.Runtime.CompilerServices.RefSafetyRules(11)]

public class Program
{
    public static void Main()
    {
        IList list = new List<int>();
        IEnumerator enumerator = list.GetEnumerator();
        try
        {
            while (enumerator.MoveNext())
            {
                object current = enumerator.Current;
            }
        }
        finally
        {
            IDisposable disposable = enumerator as IDisposable;
            if (disposable != null)
            {
                disposable.Dispose();
            }
        }
        List<int> list2 = new List<int>();
        List<int>.Enumerator enumerator2 = list2.GetEnumerator();
        try
        {
            while (enumerator2.MoveNext())
            {
                int current2 = enumerator2.Current;
            }
        }
        finally
        {
            ((IDisposable)enumerator2).Dispose();
        }
    }
}

namespace Microsoft.CodeAnalysis
{
    [CompilerGenerated]
    [Embedded]
    internal sealed class EmbeddedAttribute : Attribute
    {
    }
}

namespace System.Runtime.CompilerServices
{
    [CompilerGenerated]
    [Microsoft.CodeAnalysis.Embedded]
    [AttributeUsage(AttributeTargets.Module, AllowMultiple = false, Inherited = false)]
    internal sealed class RefSafetyRulesAttribute : Attribute
    {
        public readonly int Version;

        public RefSafetyRulesAttribute(int P_0)
        {
            Version = P_0;
        }
    }
}

​​.sharplab.json

{
    "version": 1,
    "target": "C#",
    "mode": "Debug"
}