[dotnet-sdk-10.0.100-preview.1.25103.13] Some apps retarget failed with CS0121 and CS0428 System.Linq errors

[Junjun-zhao]

Application Name: Smartstore, blog, nopCommerceNetCore
OS： Windows 10 22H2
CPU: X64
.NET Build Number: dotnet-sdk-10.0.100-preview.1.25103.13
App & Source Location checking at: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2379210

Github Link:
https://github.com/smartstore/Smartstore
https://github.com/sagebind/blog
https://github.com/nopSolutions/nopCommerce

Verify Scenarios:
1). Windows10 21h2 x64 + dotnet-sdk-8.0.405 + default target 8.0: Pass
2). Windows10 21h2 x64 + dotnet-sdk-9.0.102 + retarget 9.0: Pass
3). Windows10 21h2 x64 + dotnet-sdk-10.0.100-preview.1.25103.13 + default 8.0: Pass
4). Windows10 21h2 x64 + dotnet-sdk-10.0.100-preview.1.25103.13-win-x64 + retarget10.0: Fail

Description :
When retargeting Smartstore app to .NET 10, it is built failed with CS0212 and CS0428 errors:

error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.ToAsyncEnumerable<TSource>(System.Collections.Generic.IEnumerable<TSource>)' and 'System.Linq.AsyncEnumerable.ToAsyncEnumerable<TSource>(System.Collections.Generic.IEnumerable<TSource>)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>, System.Threading.CancellationToken)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.Where<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)' and 'System.Linq.AsyncEnumerable.Where<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.ToListAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.ToListAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.ToArrayAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.ToArrayAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.ToDictionaryAsync<TSource, TKey, TElement>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, TKey>, System.Func<TSource, TElement>, System.Collections.Generic.IEqualityComparer<TKey>?, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.ToDictionaryAsync<TSource, TKey, TElement>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, TKey>, System.Func<TSource, TElement>, System.Collections.Generic.IEqualityComparer<TKey>?, System.Threading.CancellationToken)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.CountAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.CountAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.Select<TSource, TResult>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, TResult>)' and 'System.Linq.AsyncEnumerable.Select<TSource, TResult>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, TResult>)'
error CS0428: Cannot convert method group 'Count' to non-delegate type 'int'. Did you intend to invoke the method?

Minimal Repro Steps:(Demo attached: AmbiguousCallDemo.zip)
Make sure the machine has dotnet-sdk-dotnet-sdk-10.0.100-preview.1.25103.13 installed.

1. Create a .NET 9 Console project.
2. Install latest version of System.Linq.Async nuget package.
3. Add a Test.cs class file with below code:

 public interface ITestInterface
 {
     IEnumerable<string> EnumerateFiles(string? pattern = "*", bool deep = false)
         => throw new NotImplementedException();

     IAsyncEnumerable<string> EnumerateFilesAsync(string? pattern = "*", bool deep = false, CancellationToken cancelToken = default)
        => EnumerateFiles(pattern, deep).ToAsyncEnumerable();

     //IAsyncEnumerable<string> EnumerateFilesAsync(string? pattern = "*", bool deep = false, CancellationToken cancelToken = default)
     //    => EnumerateFiles(pattern, deep).ToAsyncEnumerable();

     async ValueTask<int> CountFilesAsync(string? pattern = "*", bool deep = true, CancellationToken cancelToken = default)
         => await EnumerateFilesAsync(pattern, deep, cancelToken).CountAsync(cancellationToken: cancelToken);

 }

 public partial interface IRuleService
 {
     Task<ITestInterface> CreateExpressionGroupAsync(int ruleSetId, bool includeHidden = false);
 }

 public static class TestStaticClass
 {
     private static readonly IRuleService _ruleService;

     public static IAsyncEnumerable<TResult> SelectAwait<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, Task<TResult>> selector)
     {
         return source.ToAsyncEnumerable().SelectAwait(x => new ValueTask<TResult>(selector(x)));
     }


     public static void TestMethod()
     {
         int[] ruleSetIds = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };

         var expressions = ruleSetIds
             .SelectAwait(id => _ruleService.CreateExpressionGroupAsync(id))
             .Where(x => x != null);

         var expressions2 = ruleSetIds
             .SelectAwait(id => _ruleService.CreateExpressionGroupAsync(id))
             .ToArrayAsync();

         var expressions3 = ruleSetIds
             .SelectAwait(id => _ruleService.CreateExpressionGroupAsync(id))
             .Take(1);

         var expressions4 = ruleSetIds
             .SelectAwait(id => _ruleService.CreateExpressionGroupAsync(id))
             .Select(i => i != null);

         var expressions5 = ruleSetIds
              .SelectAwait(id => _ruleService.CreateExpressionGroupAsync(id))
              .AnyAsync();
     }
 }

 internal class CachingResult<TResult, TEntity>
 {
     public async Task<(object Value, int Count)> ConvertQueryAsyncResult(TResult queryResult)
     {
         object result = queryResult;
         var list = await ((IAsyncEnumerable<TEntity>)result).ToListAsync();
         return (list, list.Count);
     }
 }

6. Retarget the project to .NET 10:

<PropertyGroup>
  <OutputType>Exe</OutputType>
  <TargetFramework>net10.0</TargetFramework>
  <ImplicitUsings>enable</ImplicitUsings>
  <Nullable>enable</Nullable>
</PropertyGroup>

7. Build the project.

Expected Result:
Build successful.

Actual Result:
Build Failed with below errors:

error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.ToListAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.ToListAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)'
error CS0428: Cannot convert method group 'Count' to non-delegate type 'int'. Did you intend to invoke the method?
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.ToAsyncEnumerable<TSource>(System.Collections.Generic.IEnumerable<TSource>)' and 'System.Linq.AsyncEnumerable.ToAsyncEnumerable<TSource>(System.Collections.Generic.IEnumerable<TSource>)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.CountAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.CountAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.ToAsyncEnumerable<TSource>(System.Collections.Generic.IEnumerable<TSource>)' and 'System.Linq.AsyncEnumerable.ToAsyncEnumerable<TSource>(System.Collections.Generic.IEnumerable<TSource>)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.Where<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)' and 'System.Linq.AsyncEnumerable.Where<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, bool>)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.ToArrayAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.ToArrayAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.Take<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, int)' and 'System.Linq.AsyncEnumerable.Take<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, int)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.Select<TSource, TResult>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, TResult>)' and 'System.Linq.AsyncEnumerable.Select<TSource, TResult>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Func<TSource, TResult>)'
error CS0121: The call is ambiguous between the following methods or properties: 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)' and 'System.Linq.AsyncEnumerable.AnyAsync<TSource>(System.Collections.Generic.IAsyncEnumerable<TSource>, System.Threading.CancellationToken)'

DotNet Info:

.NET SDK:
 Version:           10.0.100-preview.1.25103.13
 Commit:            9035d02b05
 Workload version:  10.0.100-manifests.bf5105ba
 MSBuild version:   17.14.0-preview-25073-02+291a81087

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19045
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\10.0.100-preview.1.25103.13\

Host:
  Version:      10.0.0-preview.1.25080.5
  Architecture: x64
  Commit:       b98cabca12

.NET SDKs installed:
  10.0.100-preview.1.25103.13 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 10.0.0-preview.1.25103.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 10.0.0-preview.1.25080.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 10.0.0-preview.1.25080.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Findings:
After investigating, we found all the methods or properties thrown from errors come from System.Linq.Async nuget package.

@dotnet-actwx-bot @dotnet/compat

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I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[Junjun-zhao]

@marcpopMSFT Could you please have a look at this bug and help triage it? Thanks！

[Junjun-zhao]

@jcouv Could you please take a look at this issue and confirm whether it is a blocker for .NET 10.0 Preview1 validation? Thanks

[jcouv]

This doesn't look like a compiler issue. The extension method is defined in two assemblies given to the compiler (details below the fold).

If you remove the reference to System.Linq.Async then things compile file.
Is the problem that this test was using a nuget package which has now been replaced by APIs built into the BCL?
Tagging @stephentoub to advise.

---

First one:
System.Threading.Tasks.ValueTask<System.Collections.Generic.List<TSource>!> System.Linq.AsyncEnumerable.ToListAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource>! source, [System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)])
System.Linq.Async, Version=6.0.0.0, Culture=neutral, PublicKeyToken=94bc3704cddfc263

Second one:
System.Threading.Tasks.ValueTask<System.Collections.Generic.List<TSource>!> System.Linq.AsyncEnumerable.ToListAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource>! source, [System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)])
System.Linq.AsyncEnumerable, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a

Here are the two references given to the compiler:
/reference:C:\Users\jcouv\.nuget\packages\system.linq.async\6.0.1\ref\net6.0\System.Linq.Async.dll
/reference:"C:\Program Files\dotnet\packs\Microsoft.NETCore.App.Ref\10.0.0-preview.1.25080.5\ref\net10.0\System.Linq.AsyncEnumerable.dll"

[jaredpar]

Moving to runtime as this is caused by new APIs. Will let them decide how to proceed here.

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-linq
See info in area-owners.md if you want to be subscribed.

[eiriktsarpalis]

This is something that got discussed here: #79782 (comment)

TL;DR we need a deprecation plan and document relevant workaround in cases where there are conflicts due to transitive dependencies.

[eiriktsarpalis]

@Junjun-zhao Does the workaround described here address you immediate issue?