fix generating 'virtual' modifier of properties with non-public accessor

Author: smdn

src/Smdn.Reflection.ReverseGenerating/Smdn.Reflection.ReverseGenerating/Generator.cs

@@ -1180,6 +1180,13 @@ static void AppendMethodModifiers(StringBuilder sb, MethodBase? m)
         else if (m.IsVirtual && !m.IsFinal) {
           sb.Append("virtual ");
         }
+        else if (
+          m is MethodInfo methodMayBeAccessor &&
+          methodMayBeAccessor.TryGetPropertyFromAccessorMethod(out var p) &&
+          p.GetAccessors(nonPublic: true).Any(static a => a.IsVirtual && !a.IsFinal)
+        ) {
+          sb.Append("virtual ");
+        }
       }
 
       var isAsyncStateMachine = m.GetCustomAttributesData().Any(

src/Smdn.Reflection.ReverseGenerating/Smdn.Reflection/MethodInfoAccessorMethodExtensions.cs

@@ -1,18 +1,41 @@
 // SPDX-FileCopyrightText: 2022 smdn <smdn@smdn.jp>
 // SPDX-License-Identifier: MIT
 using System;
+#if NULL_STATE_STATIC_ANALYSIS_ATTRIBUTES
+using System.Diagnostics.CodeAnalysis;
+#endif
 using System.Linq;
 using System.Reflection;
 
 namespace Smdn.Reflection;
 
 internal static class MethodInfoAccessorMethodExtensions {
   public static bool IsPropertyAccessorMethod(this MethodInfo m)
-    => m is null
-      ? throw new ArgumentNullException(nameof(m))
-      : m.DeclaringType?.GetProperties()?.FirstOrDefault(p =>
-          m == p.GetMethod || m == p.SetMethod
-        ) != null;
+    => TryGetPropertyFromAccessorMethod(m, out _);
+
+  public static bool TryGetPropertyFromAccessorMethod(
+    this MethodInfo accessor,
+#if NULL_STATE_STATIC_ANALYSIS_ATTRIBUTES
+    [NotNullWhen(true)]
+#endif
+    out PropertyInfo? property
+  )
+  {
+    if (accessor is null)
+      throw new ArgumentNullException(nameof(accessor));
+
+    const BindingFlags bindingFlags =
+      BindingFlags.Instance |
+      BindingFlags.Static |
+      BindingFlags.Public |
+      BindingFlags.NonPublic;
+
+    property = accessor.DeclaringType?.GetProperties(bindingFlags)?.FirstOrDefault(p =>
+      accessor == p.GetMethod || accessor == p.SetMethod
+    );
+
+    return property is not null;
+  }
 
   public static bool IsEventAccessorMethod(this MethodInfo m)
     => m is null

tests/Smdn.Reflection.ReverseGenerating/Smdn.Reflection.ReverseGenerating/Generator.MemberDeclaration.cs

@@ -524,6 +524,33 @@ public abstract class Modifiers_NewVirtual : Modifiers_Abstract {
           [MemberDeclarationTestCase("new protected virtual int PProtectedVirtual { private get; set; }")] new protected virtual int PProtectedVirtual { private get; set; }
         }
 
+        public class Modifiers_Virtual_WithAccessorAccessiblity {
+          [MemberDeclarationTestCase("public virtual int PVirtualWithPrivateGetter { private get; set; }")] public virtual int PVirtualWithPrivateGetter { private get; set; }
+          [MemberDeclarationTestCase("public virtual int PVirtualWithPrivateSetter { get; private set; }")] public virtual int PVirtualWithPrivateSetter { get; private set; }
+
+          [MemberDeclarationTestCase("public virtual int PVirtual { get; }")] public virtual int PVirtual { get; }
+          [MemberDeclarationTestCase("public virtual int PVirtualWithProtectedGetter { protected get; set; }")] public virtual int PVirtualWithProtectedGetter { protected get; set; }
+          [MemberDeclarationTestCase("public virtual int PVirtualWithProtectedSetter { get; protected set; }")] public virtual int PVirtualWithProtectedSetter { get; protected set; }
+        }
+
+        public class Modifiers_Override_WithAccessorAccessiblity : Modifiers_Virtual_WithAccessorAccessiblity {
+          [MemberDeclarationTestCase("public override int PVirtual { get; }")] public override int PVirtual { get => throw null; }
+          [MemberDeclarationTestCase("public override int PVirtualWithProtectedGetter { set; }")] public override int PVirtualWithProtectedGetter { set => throw null; }
+          [MemberDeclarationTestCase("public override int PVirtualWithProtectedSetter { get; }")] public override int PVirtualWithProtectedSetter { get => throw null; }
+        }
+
+        public class Modifiers_SealedOverride_WithAccessorAccessiblity : Modifiers_Virtual_WithAccessorAccessiblity {
+          [MemberDeclarationTestCase("public sealed override int PVirtual { get; }")] public sealed override int PVirtual { get => throw null; }
+          [MemberDeclarationTestCase("public sealed override int PVirtualWithProtectedGetter { protected get; set; }")] public sealed override int PVirtualWithProtectedGetter { protected get => throw null; set => throw null;  }
+          [MemberDeclarationTestCase("public sealed override int PVirtualWithProtectedSetter { get; protected set; }")] public sealed override int PVirtualWithProtectedSetter { get => throw null; protected set => throw null; }
+        }
+
+        public class Modifiers_NewVirtual_WithAccessorAccessiblity : Modifiers_Virtual_WithAccessorAccessiblity {
+          [MemberDeclarationTestCase("new public virtual int PVirtual { get; }")] public new virtual int PVirtual { get; }
+          [MemberDeclarationTestCase("new public virtual int PVirtualWithProtectedGetter { private get; set; }")] new public virtual int PVirtualWithProtectedGetter { /* changes accessibility */ private get; set; }
+          [MemberDeclarationTestCase("new public virtual int PVirtualWithProtectedSetter { get; private set; }")] public new virtual int PVirtualWithProtectedSetter { get; /* changes accessibility */ private set; }
+        }
+
         public class Indexers1 {
           [IndexerName("Indexer")]
           [MemberDeclarationTestCase("public int this[int x] { get; set; }")]