make the workaround for nullability of by-ref types configurable with DefineConstants

Author: smdn

src/Smdn.Reflection.ReverseGenerating/Smdn.Reflection.ReverseGenerating.csproj

@@ -18,6 +18,9 @@ SPDX-License-Identifier: MIT
         $(TargetFramework.StartsWith('netstandard2'))
       )
     ">$(DefineConstants);CAN_OVERRIDE_CUSTOMATTRIBUTEDATA_ATTRIBUTETYPE</DefineConstants>
+    <DefineConstants Condition="
+      $(TargetFramework.StartsWith('net6.0'))
+    ">$(DefineConstants);WORKAROUND_NULLABILITYINFO_BYREFTYPE</DefineConstants>
   </PropertyGroup>
 
   <Import Project="..\Sdk.net7.0-preview.props" />

src/Smdn.Reflection.ReverseGenerating/Smdn.Reflection.ReverseGenerating/CSharpTypeFormatter.FormatTypeName.cs

@@ -14,6 +14,9 @@ internal readonly record struct FormatTypeNameOptions(
     bool TypeWithNamespace,
     bool WithDeclaringTypeName,
     bool TranslateLanguagePrimitiveType,
+#if SYSTEM_REFLECTION_NULLABILITYINFOCONTEXT && WORKAROUND_NULLABILITYINFO_BYREFTYPE
+    NullabilityInfoContext? NullabilityInfoContext = null,
+#endif
     Func<Type, string, string>? GenericParameterNameModifier = null,
     bool OmitAttributeSuffix = false
 #pragma warning restore SA1313
@@ -58,6 +61,9 @@ public static string FormatTypeName(
           AttributeProvider: f,
           TypeWithNamespace: typeWithNamespace,
           WithDeclaringTypeName: withDeclaringTypeName,
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
+          NullabilityInfoContext: nullabilityInfoContext,
+#endif
           TranslateLanguagePrimitiveType: translateLanguagePrimitiveType
         )
       ).ToString();
@@ -101,6 +107,9 @@ public static string FormatTypeName(
           AttributeProvider: p,
           TypeWithNamespace: typeWithNamespace,
           WithDeclaringTypeName: withDeclaringTypeName,
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
+          NullabilityInfoContext: nullabilityInfoContext,
+#endif
           TranslateLanguagePrimitiveType: translateLanguagePrimitiveType
         )
       ).ToString();
@@ -144,6 +153,9 @@ public static string FormatTypeName(
           AttributeProvider: p,
           TypeWithNamespace: typeWithNamespace,
           WithDeclaringTypeName: withDeclaringTypeName,
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
+          NullabilityInfoContext: nullabilityInfoContext,
+#endif
           TranslateLanguagePrimitiveType: translateLanguagePrimitiveType
         )
       ).ToString();
@@ -187,6 +199,9 @@ public static string FormatTypeName(
           AttributeProvider: ev,
           TypeWithNamespace: typeWithNamespace,
           WithDeclaringTypeName: withDeclaringTypeName,
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
+          NullabilityInfoContext: nullabilityInfoContext,
+#endif
           TranslateLanguagePrimitiveType: translateLanguagePrimitiveType
         )
       ).ToString();

src/Smdn.Reflection.ReverseGenerating/Smdn.Reflection.ReverseGenerating/CSharpTypeFormatter.FormatTypeNameWithNullabilityAnnotation.cs

@@ -15,6 +15,8 @@ namespace Smdn.Reflection.ReverseGenerating;
 #pragma warning disable IDE0040
 static partial class CSharpFormatter {
 #pragma warning restore IDE0040
+
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
   // Workaround: The pseudo ParameterInfo type which unwraps 'ByRef' type to its element type
   // See https://github.com/dotnet/runtime/issues/72320
   private sealed class ByRefElementTypeParameterInfo : ParameterInfo {
@@ -30,6 +32,7 @@ public ByRefElementTypeParameterInfo(ParameterInfo baseParam)
     public override IList<CustomAttributeData> GetCustomAttributesData()
       => BaseParameter.GetCustomAttributesData();
   }
+#endif
 
   private static StringBuilder FormatTypeNameWithNullabilityAnnotation(
     NullabilityInfo target,
@@ -45,7 +48,9 @@ static string GetNullabilityAnnotation(NullabilityInfo target)
         : string.Empty;
 
     if (target.Type.IsByRef) {
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
       var elementTypeNullabilityInfo = target.ElementType;
+#endif
 
       if (options.AttributeProvider is ParameterInfo p) {
         // retval/parameter modifiers
@@ -56,20 +61,30 @@ static string GetNullabilityAnnotation(NullabilityInfo target)
         else /*if (p.IsRetval)*/
           builder.Append("ref ");
 
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
         // [.net6.0] Currently, NullabilityInfo.ElementType is always null if the type is ByRef.
         // Uses the workaround implementation instead in that case.
         // See https://github.com/dotnet/runtime/issues/72320
-        if (target.ElementType is null && p.ParameterType.HasElementType)
-          elementTypeNullabilityInfo = new NullabilityInfoContext().Create(new ByRefElementTypeParameterInfo(p)); // TODO: context
+        if (options.NullabilityInfoContext is not null && target.ElementType is null && p.ParameterType.HasElementType)
+          elementTypeNullabilityInfo = options.NullabilityInfoContext.Create(new ByRefElementTypeParameterInfo(p));
+#endif
       }
 
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
       if (elementTypeNullabilityInfo is not null) {
         return FormatTypeNameWithNullabilityAnnotation(
           elementTypeNullabilityInfo,
           builder,
           options
         );
       }
+#else
+      return FormatTypeNameWithNullabilityAnnotation(
+        target.ElementType!,
+        builder,
+        options
+      );
+#endif
     }
 
     if (target.Type.IsArray) {
@@ -115,8 +130,12 @@ static string GetNullabilityAnnotation(NullabilityInfo target)
     else if (isGenericTypeClosedOrDefinition) {
       // other generic types
       if (targetType.IsByRef) {
+#if WORKAROUND_NULLABILITYINFO_BYREFTYPE
         // TODO: cannot get NullabilityInfo of generic type arguments from by-ref parameter type
         return builder.Append(FormatTypeNameCore(targetType, options));
+#else
+        return FormatTypeNameWithNullabilityAnnotation(target.ElementType!, builder, options);
+#endif
       }
       else {
         return FormatClosedGenericTypeOrGenericTypeDefinition(target, builder, options)