Iterating using enumerator and looping

f#

namespace FSharpHelper
{
    [CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)]
    [RequireQualifiedAccess]
    [CompilationMapping(SourceConstructFlags.Module)]
    public class MathHelper
    {
        [CompilationSourceName("sumEnum")]
        public static T SumEnum<T>(FSharpList<T> list)
        {
            IEnumerator<T> enumerator = ((IEnumerable<T>)list).GetEnumerator();
            try
            {
                T x = LanguagePrimitives.GenericZeroDynamic<T>();
                while (enumerator.MoveNext())
                    x = LanguagePrimitives.AdditionDynamic<T, T, T>(x, enumerator.Current);
                return x;
            }
            finally
            {
                IDisposable disposable = enumerator as IDisposable;
                if (disposable != null)
                    disposable.Dispose();
            }
        }

        [CompilationArgumentCounts(new int[] { 1, 1 })]
        [CompilationSourceName("sumLoop")]
        public static T SumLoop<T>(FSharpList<T> xs)
        {
            // ISSUE: reference to a compiler-generated field
            T s  = default(T);
            while (xs.TailOrNull != null)
            {
                FSharpList<T> fsharpList1 = xs;
                // ISSUE: reference to a compiler-generated field
                FSharpList<T> fsharpList2 = fsharpList1.Tail;
                // ISSUE: reference to a compiler-generated field
                T obj = fsharpList1.Head;
                T state = LanguagePrimitives.AdditionDynamic<T, T, T>(s, obj);
                xs = fsharpList2;
                s = state;
            }
            return s;
        }

    }
}