IDE doesn't suggest upgrading LangVersion when emitting error as warning

[jjonescz]

Version Used: e1a7480

Steps to Reproduce:

<PropertyGroup>
  <LangVersion>11</LangVersion>
  <GenerateDocumentationFile>true</GenerateDocumentationFile>
</PropertyGroup>

/// <summary>
/// <see cref="M(ref readonly int)"/>
/// </summary>
class C
{
    public static void M(ref readonly int x)
    {
        Console.WriteLine(x);
    }
}

Diagnostic Id: CS1658, CS8652

Expected Behavior: Visual Studio suggests upgrading language version as a code action on the cref="M(ref readonly int)" where the following warning is reported:

CS1658: The feature 'ref readonly parameters' is currently in Preview and unsupported. To use Preview features, use the 'preview' language version.. See also error CS8652.

Actual Behavior: Visual Studio suggest upgrading language version only for error CS8652 emitted for public static void M(ref readonly int x) declaration, but not when the same error is emitted as warning inside the doc comment (implemented here - notice the forceWarning: true parameter):

roslyn/src/Compilers/CSharp/Portable/Binder/Binder_Crefs.cs

Line 938 in e1a7480

CheckFeatureAvailability(parameter.ReadOnlyKeyword, MessageID.IDS_FeatureRefReadonlyParameters, diagnostics, forceWarning: true);

Note that this example is about ref readonly parameters, but similar issue probably holds for other scenarios.

[CyrusNajmabadi]

Honestly, this seems exceedingly minor. If adding the diagnostic id for this to the upgrade fixer doesn't work, that's nbd imo. Someone is already going to have updated to the right version when they started usign teh feature in code. The subset that don't, but then want to because they referred to such a member from a doc-comment is exceedingly small.

[CyrusNajmabadi]

Closing out as too niche.