From a4bac6586d25cf1b2b1b8df6b6a7ff3cd956949e Mon Sep 17 00:00:00 2001
From: Nick Walker <nickwalk@microsoft.com>
Date: Wed, 11 Sep 2024 09:47:50 -0700
Subject: [PATCH] #945509 Support ref readonly parameters

Add support for correct rendering of "ref readonly" parameter in C#
method signature documentation.
---
 mdoc/Consts.cs                                            | 1 +
 .../Updater/Formatters/CSharpFullMemberFormatter.cs       | 8 ++++++--
 mdoc/mdoc.Test/FormatterTests.cs                          | 8 ++++++++
 mdoc/mdoc.Test/SampleClasses/SomeClass.cs                 | 4 ++++
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/mdoc/Consts.cs b/mdoc/Consts.cs
index a3aca853c..4a497c810 100644
--- a/mdoc/Consts.cs
+++ b/mdoc/Consts.cs
@@ -49,6 +49,7 @@ public static class Consts
         public const string CompilerGeneratedAttribute = "System.Runtime.CompilerServices.CompilerGeneratedAttribute";
         public const string IsByRefLikeAttribute = "System.Runtime.CompilerServices.IsByRefLikeAttribute";
         public const string IsReadOnlyAttribute = "System.Runtime.CompilerServices.IsReadOnlyAttribute";
+        public const string RequiresLocationAttribute = "System.Runtime.CompilerServices.RequiresLocationAttribute";
         public const string InAttribute = "System.Runtime.InteropServices.InAttribute";
         public const string OutAttribute = "System.Runtime.InteropServices.OutAttribute";
         public const string TupleElementNamesAttribute = "System.Runtime.CompilerServices.TupleElementNamesAttribute";
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
index ec0f20573..37e1b8140 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
@@ -610,7 +610,7 @@ private StringBuilder AppendParameters (StringBuilder buf, MethodDefinition meth
         protected override StringBuilder AppendParameter(StringBuilder buf, ParameterDefinition parameter)
         {
             TypeReference parameterType = parameter.ParameterType;
-            var refType = new BitArray(3);
+            var refType = new BitArray(4);
 
             if (parameter.HasCustomAttributes)
             {
@@ -641,6 +641,10 @@ protected override StringBuilder AppendParameter(StringBuilder buf, ParameterDef
                 {
                     refType.Set(0, true);
                 }
+                else if (parameter.IsIn && DocUtils.HasCustomAttribute(parameter, Consts.RequiresLocationAttribute))
+                {
+                    refType.Set(3, true);
+                }
                 else
                 {
                     refType.Set(2, true);
@@ -648,7 +652,7 @@ protected override StringBuilder AppendParameter(StringBuilder buf, ParameterDef
                 parameterType = byReferenceType.ElementType;
             }
 
-            buf.Append(refType.Get(0) ? "in " : (refType.Get(1) ? "out " : (refType.Get(2) ? "ref ": "")));
+            buf.Append(refType.Get(0) ? "in " : (refType.Get(1) ? "out " : (refType.Get(2) ? "ref ": (refType.Get(3) ? "ref readonly " : ""))));
 
             if (parameter.HasCustomAttributes)
             {
diff --git a/mdoc/mdoc.Test/FormatterTests.cs b/mdoc/mdoc.Test/FormatterTests.cs
index 187c7fa27..29e2373f8 100644
--- a/mdoc/mdoc.Test/FormatterTests.cs
+++ b/mdoc/mdoc.Test/FormatterTests.cs
@@ -601,6 +601,14 @@ public void CSharpStaticEventImplementation(string typeFullName, string eventNam
             TestEventSignature(staticVirtualMemberDllPath, typeFullName, eventName, expectedSignature);
         }
 
+        [TestCase("MethodWithRefReadonlyParam", "public void MethodWithRefReadonlyParam (ref readonly int i);")]
+        public void CSharpRefReadonlyTest(string methodName, string expectedSignature)
+        {
+            var method = GetMethod(typeof(SampleClasses.SomeClass), m => m.Name == methodName);
+            var methodSignature = formatter.GetDeclaration(method);
+            Assert.AreEqual(expectedSignature, methodSignature);
+        }
+
         #region Helper Methods
         string RealTypeName(string name){
             switch (name) {
diff --git a/mdoc/mdoc.Test/SampleClasses/SomeClass.cs b/mdoc/mdoc.Test/SampleClasses/SomeClass.cs
index 7e7d2dae1..7ddadfbd7 100644
--- a/mdoc/mdoc.Test/SampleClasses/SomeClass.cs
+++ b/mdoc/mdoc.Test/SampleClasses/SomeClass.cs
@@ -104,6 +104,10 @@ public ref T TestScopedParams<T>(scoped in T p1, scoped out T p2, scoped ref T p
             throw new PlatformNotSupportedException();
         }
 
+        public void MethodWithRefReadonlyParam(ref readonly int i)
+        {
+        }
+
         public event EventHandler<object> AppMemoryUsageIncreased;
         public static event EventHandler<object> StaticEvent;
         private static event EventHandler<object> PrivateEvent;