Allow usage of ref structs in VB despite CompilerFeatureRequired

src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.vb

@@ -1340,7 +1340,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols.Metadata.PE
         Private Function DeriveCompilerFeatureRequiredDiagnostic() As DiagnosticInfo
             Dim decoder = New MetadataDecoder(ContainingPEModule, Me)
 
-            Dim diagnostic = DeriveCompilerFeatureRequiredAttributeDiagnostic(Me, ContainingPEModule, Handle, CompilerFeatureRequiredFeatures.None, decoder)
+            Dim diagnostic = DeriveCompilerFeatureRequiredAttributeDiagnostic(Me, ContainingPEModule, Handle, CompilerFeatureRequiredFeatures.RefStructs, decoder)
 
             If diagnostic IsNot Nothing Then
                 Return diagnostic

src/Compilers/VisualBasic/Test/Semantic/Microsoft.CodeAnalysis.VisualBasic.Semantic.UnitTests.vbproj

@@ -20,6 +20,7 @@
     <ProjectReference Include="..\..\..\Test\Resources\Core\Microsoft.CodeAnalysis.Compiler.Test.Resources.csproj" />
     <ProjectReference Include="..\..\..\Test\Utilities\VisualBasic\Microsoft.CodeAnalysis.VisualBasic.Test.Utilities.vbproj" />
     <ProjectReference Include="..\..\Portable\Microsoft.CodeAnalysis.VisualBasic.vbproj" />
+    <PackageReference Include="Basic.Reference.Assemblies.Net60" Version="$(BasicReferenceAssembliesNet60Version)" />
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="System.Drawing.Common" Version="$(SystemDrawingCommonVersion)" Condition="$(TargetFramework) == 'net7.0'" />

src/Compilers/VisualBasic/Test/Semantic/Semantics/RefFieldTests.vb

@@ -16,7 +16,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests
         ''' <summary>
         ''' Ref field in ref struct.
         ''' </summary>
-        <Fact>
+        <Fact, WorkItem(65392, "https://github.com/dotnet/roslyn/issues/65392")>
         Public Sub RefField_01()
             Dim sourceA =
 "public ref struct S<T>
@@ -42,9 +42,6 @@ End Module"
 BC30668: 'S(Of Integer)' is obsolete: 'Types with embedded references are not supported in this version of your compiler.'.
         Dim s = New S(Of Integer)()
                     ~~~~~~~~~~~~~
-BC37319: 'S(Of T)' requires compiler feature 'RefStructs', which is not supported by this version of the Visual Basic compiler.
-        Dim s = New S(Of Integer)()
-                    ~~~~~~~~~~~~~
 BC30656: Field 'F' is of an unsupported type.
         Console.WriteLine(s.F)
                           ~~~
@@ -56,6 +53,33 @@ BC30656: Field 'F' is of an unsupported type.
             Assert.True(field.HasUnsupportedMetadata)
         End Sub
 
+        <Fact, WorkItem(65392, "https://github.com/dotnet/roslyn/issues/65392")>
+        Public Sub CanUsePassThroughRefStructInstances()
+            Dim source =
+"Imports System
+Module Program
+    Sub Main()
+        Dim s = ""123"".AsSpan()
+        Dim s2 As ReadOnlySpan(Of Char) = ""123"".AsSpan()
+        Dim s3 = MemoryExtensions.AsSpan(""123"")
+    End Sub
+End Module"
+
+            Dim comp = CreateCompilation(source, targetFramework:=TargetFramework.Net60)
+            comp.AssertTheseDiagnostics(<expected>
+BC30668: 'ReadOnlySpan(Of Char)' is obsolete: 'Types with embedded references are not supported in this version of your compiler.'.
+        Dim s2 As ReadOnlySpan(Of Char) = "123".AsSpan()
+                  ~~~~~~~~~~~~~~~~~~~~~
+</expected>)
+
+            comp = CreateCompilation(source, targetFramework:=TargetFramework.Net70)
+            comp.AssertTheseDiagnostics(<expected>
+BC30668: 'ReadOnlySpan(Of Char)' is obsolete: 'Types with embedded references are not supported in this version of your compiler.'.
+        Dim s2 As ReadOnlySpan(Of Char) = "123".AsSpan()
+                  ~~~~~~~~~~~~~~~~~~~~~
+</expected>)
+        End Sub
+
         ''' <summary>
         ''' Ref field in class.
         ''' </summary>