Invalid code when decompiling simple F# not (isNull x) into C#

Consider this simple code:

open System

type C() =
    member __.notNull x = not (isNull x)

(see https://sharplab.io/#v2:DYLgZgzgPg9gDgUwHYAIDKBPCAXBBbAWAChjsNEUBhACgEoUBeYlFlPfAIwQCcUB9PgDokMbADkArsGAoAHoxQjsKagEsIk6XNpA)

It decompiles into that:

using Microsoft.FSharp.Core;
using System;
using System.Reflection;
[assembly: AssemblyVersion("0.0.0.0")]
[assembly: FSharpInterfaceDataVersion(2, 0, 0)]
[CompilationMapping(SourceConstructFlags.Module)]
public static class _
{
    [CompilationMapping(SourceConstructFlags.ObjectType)]
    [Serializable]
    public class C
    {
        public C() : this()
        {
        }
        public bool notNull<a>(a x) where a : class
        {
            return x == null ? 1 : 0 == 0;
        }
    }
}
namespace <StartupCode$_>
{
    internal static class $_
    {
    }
}

That statement return x == null ? 1 : 0 == 0 is very strange because it doesn’t compile in C#.

[ashmind]

@ForNeVeR Thanks for reporting! The decompilation is currently handled by an external component (ILSpy). The version I’m using is somewhat outdated – I’ll try updating to latest sometime later and I’ll let you know if they’ve fixed it.

[ForNeVeR]

Thanks for the fix and for the clarification. I’ve updated the ILSpy issue and reclassified it as an enhancement.

(Also I can confirm that the issue has been fixed.)