C#•2y ago

✅ (solved!) "System.InvalidOperationException: Sequence contains no elements" error from Roslyn

Hi guys! I'm trying to publish my C# project using dotnet publish -c Debug --nologo -r win-x64, but I'm getting a cryptic error message, which I've attached to this post. (<MSBuild> refers to C:\Program Files\dotnet\sdk\<version>\Roslyn\Microsoft.CSharp.Core.targets) I have no idea how to fix this, to be honest - I've looked this up on Google but to no avail. I'm using shared projects, so maybe that's causing some issues...?

28 Replies

ascpixiOP•2y ago

Here's the full log:

message.txt

Thinker•2y ago

Looks like a Roslyn bug?

ascpixiOP•2y ago

that's what i hope is not the case... i'm looking at the -v diag output right now, but that doesn't really give me any clues on what's happening if that is a roslyn bug, a repro case would be extremely difficult to create because i don't even know what causes it xd

Thinker•2y ago

You can try asking in #roslyn since someone there might have more insight regarding the stack trace

ascpixiOP•2y ago

this is what it spits out right before crashing

message.txt

ascpixiOP•2y ago

alright, i'll send a link to the thread there

youssef13•2y ago

This should be a Roslyn bug. You need to open an issue at dotnet/roslyn repository, and it would be great if you can upload a repro project to the issue

ascpixiOP•2y ago

i identified what line caused the error after removing this specific line, the error disappears (more appear, but they're unrelated)

            uint hc1 = (uint)(value1?.GetHashCode() ?? 0);

            uint hc1 = (uint)(value1?.GetHashCode() ?? 0);

but that's such a random line for it to fail on... alright i have no idea why removing that one line does anything, i tried putting what crashes in my solution into a new one and it compiles fine

sanic•2y ago

what's the type of value1? Are you able to share the project which the compiler is crashing on?

ascpixiOP•2y ago

i'm working on a repro project right now, it really does seem that line causes the issue since i'm able to get it to get to the linking stage (which ofc is dependent on roslyn working) value1 is T (it's a generic method) alright oddly enough now when i uncomment it now it works correctly??

sanic•2y ago

version of the compiler in use? (can determine by adding #error version to your code)

ascpixiOP•2y ago

Compiler version: '4.4.0-6.22608.27 (af1e46ad)

sanic•2y ago

I think the crash is going through this path https://sourceroslyn.io/#Microsoft.CodeAnalysis.CSharp/Lowering/LocalRewriter/LocalRewriter_ConditionalAccess.cs,136

ascpixiOP•2y ago

oh yep i fixed link errors and im getting that error again

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;

namespace System
{
    public static class HashCode
    {
        const uint EmptyState = 1;

        public static int Combine<T1>(T1 value1)
        {
            uint hc1 = (uint)(value1?.GetHashCode() ?? 0);

            uint hash = EmptyState;
            hash += 4;

            hash = QueueRound(hash, hc1);

            hash = MixFinal(hash);
            return (int)hash;
        }

        private static uint MixFinal(uint hash)
        {
            return 0;
        }

        private static uint QueueRound(uint hash, uint queuedValue)
        {
            return 0;
        }

        private static uint Round(uint hash, uint input)
        {
            return 0;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;

namespace System
{
    public static class HashCode
    {
        const uint EmptyState = 1;

        public static int Combine<T1>(T1 value1)
        {
            uint hc1 = (uint)(value1?.GetHashCode() ?? 0);

            uint hash = EmptyState;
            hash += 4;

            hash = QueueRound(hash, hc1);

            hash = MixFinal(hash);
            return (int)hash;
        }

        private static uint MixFinal(uint hash)
        {
            return 0;
        }

        private static uint QueueRound(uint hash, uint queuedValue)
        {
            return 0;
        }

        private static uint Round(uint hash, uint input)
        {
            return 0;
        }
    }
}

maybe it's something to do with shared projects...? they are very buggy in my experience i did

    <Compile Include="$(MSBuildThisFileDirectory)**\*.cs" />

    <Compile Include="$(MSBuildThisFileDirectory)**\*.cs" />

and VS does not play well with that but if i don't do that, then it wants to add an entry to the projitems for every file deleted/added, which is very prone to merge conflicts

sanic•2y ago

I think this is saying: the type of the a?.b expression is a Nullable, so we essentially want to make an expression like new int?(a.b), and for some reason, we found no constructor on int? with a single parameter. Is there any chance your project is referencing a bogus definition of System.Nullable?

ascpixiOP•2y ago

oh, yeah! i don't have a single param constructor there

using System;
using System.Collections.Generic;

namespace System
{
    /// <summary>
    /// Represents a value type that can be assigned <see langword="null"/>.
    /// </summary>
    /// <typeparam name="T">The underlying value type of the <see cref="Nullable{T}"/> generic type.</typeparam>
    public struct Nullable<T> where T : struct
    {
        private readonly bool _hasValue;
        private T _value;

        /// <summary>
        /// Gets a value indicating whether the current <see cref="Nullable{T}"/> object has a valid value of its underlying type.
        /// </summary>
        public bool HasValue => _hasValue;

        /// <summary>
        /// Gets the value of the current <see cref="Nullable{T}"/> object if it has been assigned a valid underlying value.
        /// </summary>
        /// <exception cref="InvalidOperationException">Thrown when the <see cref="HasValue"/> property is <see langword="false"/>.</exception>
        public T Value {
            get {
                if(!_hasValue) {
                    throw new InvalidOperationException("Nullable object must have a value.");
                }

                return _value;
            }
        }
    }
}

using System;
using System.Collections.Generic;

namespace System
{
    /// <summary>
    /// Represents a value type that can be assigned <see langword="null"/>.
    /// </summary>
    /// <typeparam name="T">The underlying value type of the <see cref="Nullable{T}"/> generic type.</typeparam>
    public struct Nullable<T> where T : struct
    {
        private readonly bool _hasValue;
        private T _value;

        /// <summary>
        /// Gets a value indicating whether the current <see cref="Nullable{T}"/> object has a valid value of its underlying type.
        /// </summary>
        public bool HasValue => _hasValue;

        /// <summary>
        /// Gets the value of the current <see cref="Nullable{T}"/> object if it has been assigned a valid underlying value.
        /// </summary>
        /// <exception cref="InvalidOperationException">Thrown when the <see cref="HasValue"/> property is <see langword="false"/>.</exception>
        public T Value {
            get {
                if(!_hasValue) {
                    throw new InvalidOperationException("Nullable object must have a value.");
                }

                return _value;
            }
        }
    }
}

lemme implement one real quick

Thinker•2y ago

Is this a polyfill or something?

ascpixiOP•2y ago

yyyyep, seems to be it... nope

sanic•2y ago

ascpixiOP•2y ago

i'm implementing my own runtime osdev with C#, very novel concept

sanic•2y ago

Well! I'm glad I could help figure it out..

Thinker•2y ago

wow, that's cool

ascpixiOP•2y ago

yeah, thanks for the help!!

sanic•2y ago

It might be good if you could file a bug on us If compiler needs to use a well-known member like this, we usually want it to report a binding-time error if the member doesn't exist Not sure if bug will be prioritized 😉 but good to have a record of it.

ascpixiOP•2y ago

what repo is best to file it under? dotnet/roslyn?

ascpixiOP•2y ago

https://github.com/dotnet/roslyn/issues/67709 issue filed! (hope the maintainers aren't gonna laugh at me since this is such a specific issue lol)

GitHub

Missing Nullable(T) constructor triggers an LINQ empty sequence exc...

Version Used: 4.4.0-6.22608.27 (af1e46a) Steps to Reproduce: Create an MSBuild NativeAOT C# project, and set <NoStdLib> to true. Create a basic runtime implementation. The ZeroSharp no-runtim...

sanic•2y ago

thanks! And don't worry about it. 🙂 These are bugs we would probably file on ourselves if we discovered them, even if we might not go out of our way to fix them.

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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✅ (solved!) "System.InvalidOperationException: Sequence contains no elements" error from Roslyn