False-positive for VSTHRD110 when an incompatible GetAwaiter extension method is available

[meziantou]

Bug description

VSTHRD110 detects a GetAwaiter method is available from an extension method. However, the GetAwaiter method is not compatible with the actual result, so the code cannot be fixed.

TaskAwaiter<(T1, T2)> GetAwaiter<T1, T2>(this (Task<T1>, Task<T2>) tasks) is not compatible with (int,int).

Repro steps

• dotnet new console
• dotnet add package Microsoft.VisualStudio.Threading.Analyzers --version 17.5.22
• Replace the Program.cs with the following content

using System.Runtime.CompilerServices;

var stack = new Stack<(int, int)>();
stack.Pop(); // <-- VSTHRD110, but the result (int,int) cannot be awaited.

internal static class Extensions
{

    public static TaskAwaiter<(T1, T2)> GetAwaiter<T1, T2>(this (Task<T1>, Task<T2>) tasks)
    {
        throw new NotImplementedException();
    }
}

• dotnet build
• => Program.cs(4,1): warning VSTHRD110: Observe the awaitable result of this method call by awaiting it, assigning to a variable, or passing it to another method

Expected behavior

No diagnostic as there is no compatible GetAwaiter method to use await.

Actual behavior

VSTHRD110 is reported

Additional context

dotnet --info

.NET SDK:
 Version:   7.0.200
 Commit:    534117727b

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.22623
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\7.0.200\

Host:
  Version:      7.0.3
  Architecture: x64
  Commit:       0a2bda10e8

.NET SDKs installed:
  7.0.103 [C:\Program Files\dotnet\sdk]
  7.0.200 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 6.0.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 7.0.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  x86   [C:\Program Files (x86)\dotnet]
    registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
  Not set

global.json file:
  Not found

[drewnoakes]

Interestingly I don't reproduce this with our TupleTaskAwaiter code.

https://github.com/dotnet/project-system/blob/1976cf850f36c022d110abc01a90356a85021676/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/Utilities/TupleTaskExtensions.cs#L17