Support ref readonly parameters (#712)

Add support for correct rendering of "ref readonly" parameter in C#
method signature documentation.

---------

Co-authored-by: Yifan Bian <[email protected]>

Author: nickwalkmsft

external/Test/RefReadonlyParameter.dll

@@ -3,7 +3,7 @@ namespace Mono.Documentation
 {
     public static class Consts
     {
-        public static string MonoVersion = "5.9.4";
+        public static string MonoVersion = "5.9.5";
         public const string DocId = "DocId";
         public const string CppCli = "C++ CLI";
         public const string CppCx = "C++ CX";
@@ -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";

mdoc/Consts.cs

@@ -619,7 +619,7 @@ 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)
             {
@@ -650,14 +650,18 @@ 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);
                 }
                 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)
             {

mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs

@@ -619,6 +619,12 @@ public void CSharpAllowsRefStructForMemberTest(string typeFullName, string metho
             TestMethodSignature(allowsRefStructDllPath, typeFullName, methodName, expectedSignature);
         }
 
+        [TestCase("SomeClass", "MethodWithRefReadOnlyParam", "public void MethodWithRefReadOnlyParam (ref readonly int i);")]
+        public void CSharpRefReadonlyTest(string typeFullName, string methodName, string expectedSignature)
+        {
+            TestMethodSignature("../../../../external/Test/RefReadonlyParameter.dll", typeFullName, methodName, expectedSignature);
+        }
+
         #region Helper Methods
         string RealTypeName(string name){
             switch (name) {

mdoc/mdoc.Test/FormatterTests.cs

@@ -2,7 +2,7 @@
 <package >
   <metadata>
     <id>mdoc</id>
-    <version>5.9.4</version>
+    <version>5.9.5</version>
     <title>mdoc</title>
     <authors>Microsoft</authors>
     <owners>Microsoft</owners>