---

This section details on the original issue you should resolve

<issue_title>ASP0016 False positive for nested anonymous methods</issue_title>
<issue_description>You can add the following test to RequestDelegateReturnTypeAnalyzerTests.cs:

 [Fact]
 public async Task AnonymousDelegate_RequestDelegate_ReturnType_InNestedAynonymousDelegate_DoesNotReportDiagnostics()
 {
 await VerifyCS.VerifyAnalyzerAsync(@"
using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
var webApp = WebApplication.Create();
webApp.Run((context) =>
{
 Func<Task<DateTime>> _ = () => Task.FromResult(DateTime.Now);
 return Task.CompletedTask;
});
");
 }

And you'll get the following failure:

 Message: 
System.InvalidOperationException : Mismatch between number of diagnostics returned, expected "0" actual "1"
Diagnostics:
// /0/Test0.cs(6,12): warning ASP0016: The method used to create a RequestDelegate returns Task<System.DateTime>. RequestDelegate discards this value. If this isn't intended then change the return type to non-generic Task or, if the delegate is a route handler, cast it to Delegate so the return value is written to the response.
VerifyCS.Diagnostic().WithSpan(6, 12, 10, 2).WithArguments("System.DateTime"),
 Stack Trace: 
DefaultVerifier.Equal[T](T expected, T actual, String message)
AnalyzerTest`1.VerifyDiagnosticResults(IEnumerable`1 actualResults, ImmutableArray`1 analyzers, DiagnosticResult[] expectedResults, IVerifier verifier)
AnalyzerTest`1.VerifyDiagnosticsAsync(EvaluatedProjectState primaryProject, ImmutableArray`1 additionalProjects, DiagnosticResult[] expected, IVerifier verifier, CancellationToken cancellationToken)
AnalyzerTest`1.RunImplAsync(CancellationToken cancellationToken)
AnalyzerTest`1.RunAsync(CancellationToken cancellationToken)
CSharpAnalyzerVerifier`1.VerifyAnalyzerAsync(String source, DiagnosticResult[] expected) line 46
RequestDelegateReturnTypeAnalyzerTests.AnonymousDelegate_RequestDelegate_ReturnType_InNestedAynonymousDelegate_DoesNotReportDiagnostics() line 73
--- End of stack trace from previous location ---

This is incorrect because the Task<System.DateTime> is not being returned directly from the anonymous RequestDelegate, but instead an inner anonymous method which is not a RequestDelegate. This was uncovered by #64120 which resulted in the following line getting incorrectly flagged by ASP0016 even though the lambda calling UpgradeAsync() and returning a Task<Stream> was being passed to ThrowsAsync as a Func<Task<Stream>> and was never converted to a RequestDelegate.

aspnetcore/src/Servers/IIS/IIS/test/testassets/InProcessWebSite/Startup.WebSockets.cs

Line 101 in a9e3c6a

var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => upgradeFeature.UpgradeAsync());

D:\a\_work1円\s\src\Servers\IIS\IIS\test\testassets\InProcessWebSite\Startup.WebSockets.cs(98,17): error ASP0016: The method used to create a RequestDelegate returns Task<System.IO.Stream>. RequestDelegate discards this value. If this isn't intended then change the return type to non-generic Task or, if the delegate is a route handler, cast it to Delegate so the return value is written to the response. (https://aka.ms/aspnet/analyzers) [D:\a\_work1円\s\src\Servers\IIS\IIS\test\testassets\InProcessNewShimWebSite\InProcessNewShimWebSite.csproj::TargetFramework=net8.0]
##[error]src\Servers\IIS\IIS\test\testassets\InProcessWebSite\Startup.WebSockets.cs(98,17): error ASP0016: (NETCORE_ENGINEERING_TELEMETRY=Build) The method used to create a RequestDelegate returns Task<System.IO.Stream>. RequestDelegate discards this value. If this isn't intended then change the return type to non-generic Task or, if the delegate is a route handler, cast it to Delegate so the return value is written to the response. (https://aka.ms/aspnet/analyzers)

https://dev.azure.com/dnceng-public/public/_build/results?buildId=1186969&view=logs&jobId=1e4c7542-9334-5468-a143-1d4c0c4c3006%3Fpr%3D64120&j=4192b01c-4527-54c8-cf65-dc27f588da45&t=ee2d7ee8-2075-51eb-eb72-626500250fa2&s=d654deb9-056d-50a2-1717-90c08683d50a

@JamesNK </issue_description>

<agent_instructions>Fix RequestDelegateReturnTypeAnalyzer so when it recurses over the operations in anonymousFunction.Body it avoids considering the IReturnOperation that belong to nested IAnonymousFunctionOperation.</agent_instructions>

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