Request delegate generator produces CS8073 for ValueTask<T?> results

[gfoidl]

Is there an existing issue for this?

• [X] I have searched the existing issues

Describe the bug

For delegates that return `ValueTask<T?>? the compiler emits

Warning	CS8073	The result of the expression is always 'false' since a value of type 'ValueTask<Person>' is never equal to 'null' of type 'ValueTask<Person>?'

This is especially cumbersome when

<TreatWarningsAsErrors>true</TreatWarningsAsErrors>

is set.

Expected Behavior

No warning is produced.

Steps To Reproduce

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
WebApplication app = builder.Build();

Person[] persons = [new Person("Batman"), new Person("Me")];

// No problem
Person? SearchPerson0(string name) => Array.Find(persons, p => p.Name == name);

// Here the ValueTask causes the CS8073
ValueTask<Person?> SearchPerson1(string name)
{
    Person? person = Array.Find(persons, p => p.Name == name);
    return ValueTask.FromResult(person);
}

// This is fine, as Task is a reference type
Task<Person?> SearchPerson2(string name)
{
    Person? person = Array.Find(persons, p => p.Name == name);
    return Task.FromResult(person);
}

app.MapGet("person0/{name}", SearchPerson0);
app.MapGet("person1/{name}", SearchPerson1);
app.MapGet("person2/{name}", SearchPerson2);

app.Run();

public record Person(string Name);

<Project Sdk="Microsoft.NET.Sdk.Web">

    <PropertyGroup>
        <TargetFramework>net8.0</TargetFramework>
        <Nullable>enable</Nullable>
        <ImplicitUsings>enable</ImplicitUsings>
    </PropertyGroup>

    <PropertyGroup>
        <IncludeOpenAPIAnalyzers>true</IncludeOpenAPIAnalyzers>

        <EnableRequestDelegateGenerator>true</EnableRequestDelegateGenerator>
        <InterceptorsPreviewNamespaces>$(InterceptorsPreviewNamespaces);Microsoft.AspNetCore.Http.Generated</InterceptorsPreviewNamespaces>
    </PropertyGroup>

</Project>

Exceptions (if any)

No response

.NET Version

8.0.200

Anything else?

If this got already fixed for .NET 9 is there a chance to backport it to .NET 8 as <TreatWarningsAsErrors> needs some workarounds to make it compile and .NET 8 is a LTS?