Suggest adding PolySharp

[lilith]

I've recently migrated most of my nuget packages / oss projects to using PolySharp - I can set language=latest and still target .NET Standard 2.0 - it's great.
It's particularly essential for .NET 8 features, such as annotating for trimming/etc.

In Tomlyn.props, add

<PolySharpIncludeRuntimeSupportedAttributes>true</PolySharpIncludeRuntimeSupportedAttributes>

And

    <!--Polyfill language features for .NET Standard 2.0 et all, generating internal
        items only for the compiler. Enables langversion=latest-->
    <PackageReference Include="PolySharp" Version="1.*">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>

The only issue I've had with the library is that since it generates internal stuff, InternalsVisibleTo can cause duplications if there is both a mismatch on targeted frameworks and the consuming (typically unit test) project also includes it unnecessarily. Easily avoided, though.

[xoofx]

I've recently migrated most of my nuget packages / oss projects to using PolySharp - I can set language=latest and still target .NET Standard 2.0 - it's great.

Agreed. Feel free to open a PR.

[lilith]

I can do that. Could you merge or review my current one?

[xoofx]

I can do that. Could you merge or review my current one?

Oops, sorry, I retriggered the pipeline but forgot to come back to check and merge, done! 😅

[lilith]

#81