Support .NET language feature: function pointers (#623)

* Support .NET language feature: function pointers

* update

* update

* add test cases

* add test dll

* update

* Use delegate * for other languages

* update

* Fix new member added for function pointers

* update

15 files changed, 196 insertions, 18 deletions

diff --git a/external/Test/FunctionPointersTest.dll b/external/Test/FunctionPointersTest.dll
new file mode 100644
index 00000000..579f3cdc
--- /dev/null
+++ b/external/Test/FunctionPointersTest.dll
diff --git a/mdoc/Consts.cs b/mdoc/Consts.cs
index 58ea9e65..aba2fd0f 100644
--- a/mdoc/Consts.cs
+++ b/mdoc/Consts.cs
@@ -49,8 +49,10 @@ namespace Mono.Documentation
         public const string IsByRefLikeAttribute = "System.Runtime.CompilerServices.IsByRefLikeAttribute";
         public const string IsReadOnlyAttribute = "System.Runtime.CompilerServices.IsReadOnlyAttribute";
         public const string InAttribute = "System.Runtime.InteropServices.InAttribute";
+        public const string OutAttribute = "System.Runtime.InteropServices.OutAttribute";
         public const string TupleElementNamesAttribute = "System.Runtime.CompilerServices.TupleElementNamesAttribute";
         public const string IsExternalInit = "System.Runtime.CompilerServices.IsExternalInit";
         public const string NativeIntegerAttribute = "System.Runtime.CompilerServices.NativeIntegerAttribute";
+        public const string CallConvPrefix = "System.Runtime.CompilerServices.CallConv";
     }
 }
diff --git a/mdoc/Mono.Documentation/Updater/DocumentationEnumerator.cs b/mdoc/Mono.Documentation/Updater/DocumentationEnumerator.cs
index 90f533ef..3b710a98 100644
--- a/mdoc/Mono.Documentation/Updater/DocumentationEnumerator.cs
+++ b/mdoc/Mono.Documentation/Updater/DocumentationEnumerator.cs
@@ -153,6 +153,9 @@ namespace Mono.Documentation.Updater
 
                     string xmlMemberType = member.Parameters[i];
 
+                    // After we support function pointers, "method" as type should be skipped and not be compared with current function pointer type.
+                    if (xmlMemberType == "method") continue;
+
                     // TODO: take into account extension method reftype
                     bool xmlIsRefType = xmlMemberType.Contains ('&');
                     bool refTypesMatch = isRefType == xmlIsRefType;
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
index 06368855..ec625447 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs
@@ -1,6 +1,7 @@
 using Mono.Cecil;
 using Mono.Documentation.Util;
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -591,43 +592,51 @@ namespace Mono.Documentation.Updater.Formatters
             {
                 if (DocUtils.IsExtensionMethod (method))
                     buf.Append ("this ");
-                AppendParameter (buf, parameters[0]);
+                AppendParameter(buf, parameters[0]);
                 for (int i = 1; i < parameters.Count; ++i)
                 {
-                    buf.Append (", ");
-                    AppendParameter (buf, parameters[i]);
+                    buf.Append(", ");
+                    AppendParameter(buf, parameters[i]);
                 }
             }
 
             return buf.Append (end);
         }
 
-        private StringBuilder AppendParameter (StringBuilder buf, ParameterDefinition parameter)
+        protected override StringBuilder AppendParameter(StringBuilder buf, ParameterDefinition parameter)
         {
             TypeReference parameterType = parameter.ParameterType;
+            var refType = new BitArray(3);
 
             if (parameterType is RequiredModifierType requiredModifierType)
             {
+                switch(requiredModifierType.ModifierType.FullName)
+                {
+                    case Consts.InAttribute: refType.Set(0, true); break;
+                    case Consts.OutAttribute: refType.Set(1, true); break;
+                    default: break;
+                }
                 parameterType = requiredModifierType.ElementType;
             }
-
             if (parameterType is ByReferenceType byReferenceType)
             {
                 if (parameter.IsOut)
                 {
-                    buf.Append ("out ");
+                    refType.Set(1, true);
                 }
                 else if(parameter.IsIn && DocUtils.HasCustomAttribute(parameter, Consts.IsReadOnlyAttribute))
                 {
-                    buf.Append("in ");
+                    refType.Set(0, true);
                 }
                 else
                 {
-                    buf.Append("ref ");
+                    refType.Set(2, true);
                 }
                 parameterType = byReferenceType.ElementType;
             }
 
+            buf.Append(refType.Get(0) ? "in " : (refType.Get(1) ? "out " : (refType.Get(2) ? "ref ": "")));
+
             if (parameter.HasCustomAttributes)
             {
                 var isParams = parameter.CustomAttributes.Any (ca => ca.AttributeType.Name == "ParamArrayAttribute");
@@ -639,8 +648,7 @@ namespace Mono.Documentation.Updater.Formatters
             var isNullableType = context.IsNullable ();
             buf.Append (GetTypeName (parameterType, context));
             buf.Append (GetTypeNullableSymbol (parameter.ParameterType, isNullableType));
-            buf.Append (" ");
-            buf.Append (parameter.Name);
+            buf.Append (string.IsNullOrEmpty(parameter.Name) ? "" : " " + parameter.Name);
 
             if (parameter.HasDefault && parameter.IsOptional && parameter.HasConstant)
             {
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/CppFormatters/CppFullMemberFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/CppFormatters/CppFullMemberFormatter.cs
index 516c9a93..fbbc9e93 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/CppFormatters/CppFullMemberFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/CppFormatters/CppFullMemberFormatter.cs
@@ -715,7 +715,7 @@ namespace Mono.Documentation.Updater.Formatters.CppFormatters
             return buf.Append (end);
         }
 
-        protected virtual StringBuilder AppendParameter (StringBuilder buf, ParameterDefinition parameter)
+        protected override StringBuilder AppendParameter (StringBuilder buf, ParameterDefinition parameter)
         {
            if (parameter.ParameterType is ByReferenceType)
             {
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/DocTypeFullMemberFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/DocTypeFullMemberFormatter.cs
index 5c370b5d..69a36d02 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/DocTypeFullMemberFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/DocTypeFullMemberFormatter.cs
@@ -1,4 +1,7 @@
-namespace Mono.Documentation.Updater

+using Mono.Cecil;

+using System.Text;

+

+namespace Mono.Documentation.Updater

 {

     class DocTypeFullMemberFormatter : MemberFormatter

     {

@@ -20,5 +23,10 @@
         {

             get { return "+"; }

         }

+

+        protected override StringBuilder AppendParameter(StringBuilder buf, ParameterDefinition parameterDef)

+        {

+            return buf.Append(GetName(parameterDef.ParameterType, useTypeProjection: false, isTypeofOperator: false));

+        }

     }

 }
\ No newline at end of file
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/FSharpFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/FSharpFormatter.cs
index f810f1dd..f4725a6c 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/FSharpFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/FSharpFormatter.cs
@@ -692,7 +692,7 @@ namespace Mono.Documentation.Updater
             return buf;
         }
 
-        private void AppendParameter(StringBuilder buf, ParameterDefinition parameter)
+        protected override StringBuilder AppendParameter(StringBuilder buf, ParameterDefinition parameter)
         {
             bool isFSharpFunction = IsFSharpFunction(parameter.ParameterType);
             if (isFSharpFunction)
@@ -701,6 +701,7 @@ namespace Mono.Documentation.Updater
             buf.Append(typeName);
             if (isFSharpFunction)
                 buf.Append(")");
+            return buf;
         }
 
         protected override string GetPropertyDeclaration(PropertyDefinition property)
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/ILFullMemberFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/ILFullMemberFormatter.cs
index ad30e238..b54e64d9 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/ILFullMemberFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/ILFullMemberFormatter.cs
@@ -440,7 +440,7 @@ namespace Mono.Documentation.Updater.Formatters
             return buf.Append (end);
         }
 
-        private StringBuilder AppendParameter (StringBuilder buf, ParameterDefinition parameter)
+        protected override StringBuilder AppendParameter (StringBuilder buf, ParameterDefinition parameter)
         {
             if (parameter.ParameterType is ByReferenceType)
             {
@@ -599,5 +599,10 @@ namespace Mono.Documentation.Updater.Formatters
 
             return buf.ToString ();
         }
+
+        protected override void AppendFunctionPointerTypeName(StringBuilder buf, FunctionPointerType type, IAttributeParserContext context)
+        {
+            buf.Append("method");
+        }
     }
 }
\ No newline at end of file
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/JsFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/JsFormatter.cs
index dabceb3e..b7f4d25c 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/JsFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/JsFormatter.cs
@@ -136,6 +136,11 @@ namespace Mono.Documentation.Updater.Formatters
             return buf.Append(string.Join(", ", parameters.Select(i => i.Name)));
         }
 
+        protected override StringBuilder AppendParameter(StringBuilder buf, ParameterDefinition parameter)
+        {
+            return buf.Append(parameter.Name);
+        }
+
         protected MethodDefinition GetConstructor(TypeDefinition type)
         {
             return type.GetConstructors()
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/MemberFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/MemberFormatter.cs
index 6e1ca5bd..9e057319 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/MemberFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/MemberFormatter.cs
@@ -1,4 +1,5 @@
 using Mono.Cecil;
+using Mono.Documentation.Updater.Formatters;
 using Mono.Documentation.Util;
 using System;
 using System.Collections.Generic;
@@ -131,6 +132,69 @@ namespace Mono.Documentation.Updater
             return AppendArrayModifiers (buf, (ArrayType)type);
         }
 
+        protected virtual void AppendFunctionPointerTypeName(StringBuilder buf, FunctionPointerType type, IAttributeParserContext context)
+        {
+            buf.Append("delegate*");
+
+            var callingConvention = GetCallingConvention(type);
+            if (callingConvention != MethodCallingConvention.Default.ToString())
+            {
+                buf.Append(" unmanaged");
+                if (!string.IsNullOrEmpty(callingConvention))
+                {
+                    buf.Append("[").Append(callingConvention).Append("]");
+                }
+            }
+
+            buf.Append("<");
+            if (type.Parameters?.Count > 0)
+            {
+                for (int i = 0; i < type.Parameters.Count; i++)
+                {
+                    AppendParameter(buf, type.Parameters[i]);
+                    buf.Append(", ");
+                }
+            }
+            AppendReturnTypeName(buf, type, true);
+            buf.Append(">");
+        }
+
+        private string GetCallingConvention(FunctionPointerType type)
+        {
+            var callingConvention = type.CallingConvention.ToString("D");
+            // Cecil lib uses "9" to stands for "Unmanaged Ext"
+            if (callingConvention != "9")
+            {
+                return NormalizeCallingConvention(type.CallingConvention);
+            }
+            else
+            {
+                StringBuilder buf = new StringBuilder();
+                AssembleCallingConvention(type.ReturnType, buf);
+                return buf.ToString();
+            }
+        }
+
+        private string NormalizeCallingConvention(MethodCallingConvention callingConvention)
+        {
+            if (callingConvention == MethodCallingConvention.C) return "Cdecl";
+            var callConv = callingConvention.ToString().ToLower();
+            return char.ToUpper(callConv[0]) + callConv.Substring(1);
+        }
+
+        private void AssembleCallingConvention(TypeReference type, StringBuilder buf)
+        {
+            if (!(type is OptionalModifierType optionalModifierType)) return;
+
+            var modifier = optionalModifierType.ModifierType.FullName;
+            if (modifier.StartsWith(Consts.CallConvPrefix))
+            {
+                if (!string.IsNullOrEmpty(buf.ToString())) buf.Append(", ");
+                buf.Append(modifier.Substring(Consts.CallConvPrefix.Length));
+                AssembleCallingConvention(optionalModifierType.ElementType, buf);
+            }
+        }
+
         protected virtual bool ShouldStripModFromTypeName
         {
             get => true;
@@ -168,6 +232,11 @@ namespace Mono.Documentation.Updater
                 AppendPointerTypeName (interimBuilder, type, context);
                 return SetBuffer(buf, interimBuilder, useTypeProjection: useTypeProjection);
             }
+            if (type is FunctionPointerType functionPointerType)
+            {
+                AppendFunctionPointerTypeName(interimBuilder, functionPointerType, context);
+                return SetBuffer(buf, interimBuilder, useTypeProjection: useTypeProjection);
+            }
             if (type is GenericParameter)
             {
                 AppendTypeName (interimBuilder, type, context);
@@ -562,15 +631,14 @@ namespace Mono.Documentation.Updater
         }
 
 
-        private StringBuilder AppendReturnTypeName (StringBuilder buf, MethodDefinition method)
+        protected StringBuilder AppendReturnTypeName (StringBuilder buf, IMethodSignature method, bool noTrailingSpace = false)
         {
             var context = AttributeParserContext.Create (method.MethodReturnType);
             var isNullableType = context.IsNullable ();
             var returnTypeName = GetTypeName (method.ReturnType, context);
             buf.Append (returnTypeName);
             buf.Append (GetTypeNullableSymbol (method.ReturnType, isNullableType));
-            buf.Append (" ");
-
+            buf.Append (noTrailingSpace ? "" : " ");
             return buf;
         }
 
@@ -604,6 +672,11 @@ namespace Mono.Documentation.Updater
             return buf;
         }
 
+        protected virtual StringBuilder AppendParameter(StringBuilder buf, ParameterDefinition parameterDef)
+        {
+            return buf;
+        }
+
         protected virtual StringBuilder AppendGenericMethodConstraints (StringBuilder buf, MethodDefinition method)
         {
             return buf;
diff --git a/mdoc/Mono.Documentation/Updater/Formatters/VBFullMemberFormatter.cs b/mdoc/Mono.Documentation/Updater/Formatters/VBFullMemberFormatter.cs
index 6d9761f8..dbe5890b 100644
--- a/mdoc/Mono.Documentation/Updater/Formatters/VBFullMemberFormatter.cs
+++ b/mdoc/Mono.Documentation/Updater/Formatters/VBFullMemberFormatter.cs
@@ -562,7 +562,7 @@ namespace Mono.Documentation.Updater
             return buf.Append(end);
         }
 
-        private StringBuilder AppendParameter(StringBuilder buf, ParameterDefinition parameter)
+        protected override StringBuilder AppendParameter(StringBuilder buf, ParameterDefinition parameter)
         {
             if (parameter.IsOptional)
             {
diff --git a/mdoc/mdoc.Test/FormatterTests.cs b/mdoc/mdoc.Test/FormatterTests.cs
index b39d10c4..0c442f02 100644
--- a/mdoc/mdoc.Test/FormatterTests.cs
+++ b/mdoc/mdoc.Test/FormatterTests.cs
@@ -483,6 +483,35 @@ namespace mdoc.Test
             Assert.AreEqual(expectedSignature, methodSignature);
         }
 
+        [TestCase("UnsafeCombine", "public static R UnsafeCombine<T1,T2,R> (delegate*<T1, T2, R> combinator, T1 left, T2 right);")]
+        [TestCase("UnsafeCombine1", "public static R UnsafeCombine1<T1,T2,R> (delegate* unmanaged[Cdecl]<T1, T2, R> combinator, T1 left, T2 right);")]
+        [TestCase("UnsafeCombine2", "public static R UnsafeCombine2<T1,T2,T3,R> (delegate* unmanaged[Stdcall]<ref T1, in T2, out T3, R> combinator, T1 left, T2 right, T3 outVar);")]
+        [TestCase("UnsafeCombine3", "public static R UnsafeCombine3<T1,T2,R> (delegate* unmanaged[Fastcall]<T1, T2, ref R> combinator, T1 left, T2 right);")]
+        [TestCase("UnsafeCombine4", "public static R UnsafeCombine4<T1,T2,R> (delegate* unmanaged[Thiscall]<T1, T2, ref readonly R> combinator, T1 left, T2 right);")]
+        [TestCase("UnsafeCombine5", "public static void UnsafeCombine5 (delegate* unmanaged[Cdecl]<void> combinator);")]
+        [TestCase("UnsafeCombine6", "public static void UnsafeCombine6 (delegate*<delegate* unmanaged[Fastcall]<string, int>, delegate*<string, int>> combinator);")]
+        [TestCase("UnsafeCombine7", "public static delegate*<delegate* unmanaged[Thiscall]<string, int>, delegate*<string, int>> UnsafeCombine7 ();")]
+        public void CSharpFuctionPointersTest(string methodName, string expectedSignature)
+        {
+            var method = GetMethod(typeof(SampleClasses.FunctionPointers), m => m.Name == methodName);
+            var methodSignature = formatter.GetDeclaration(method);
+            Assert.AreEqual(expectedSignature, methodSignature);
+        }
+
+        [TestCase("UnsafeCombine1", "public static R UnsafeCombine1<T1,T2,R> (delegate* unmanaged<T1, T2, R> combinator, T1 left, T2 right);")]
+        [TestCase("UnsafeCombine2", "public static R UnsafeCombine2<T1,T2,R> (delegate* unmanaged[Cdecl, SuppressGCTransition]<T1, T2, R> combinator, T1 left, T2 right);")]
+        [TestCase("UnsafeCombine3", "public static R UnsafeCombine3<T1,T2,R> (delegate* unmanaged[Stdcall, MemberFunction]<T1, T2, R> combinator, T1 left, T2 right);")]
+        [TestCase("UnsafeCombine4", "public static void UnsafeCombine4 (delegate*<delegate* unmanaged[Cdecl, Fastcall]<string, int>, delegate*<string, int>> combinator);")]
+        [TestCase("UnsafeCombine5", "public static delegate* unmanaged[Cdecl, Fastcall]<delegate* unmanaged[Thiscall, MemberFunction]<string, int>, delegate*<string, int>> UnsafeCombine5 ();")]
+        public void CSharpFuctionPointersUnmanagedExtTest(string methodName, string expectedSignature)
+        {
+            var functionPointersDllPath = "../../../../external/Test/FunctionPointersTest.dll";
+            var type = GetType(functionPointersDllPath, "FunctionPointersTest.FunctionPointers");
+            var method = GetMethod(type, 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/MDocUpdaterTests.cs b/mdoc/mdoc.Test/MDocUpdaterTests.cs
index 6924df61..4f52a7d8 100644
--- a/mdoc/mdoc.Test/MDocUpdaterTests.cs
+++ b/mdoc/mdoc.Test/MDocUpdaterTests.cs
@@ -48,6 +48,18 @@ namespace mdoc.Test
 
             Assert.AreEqual("Mono_DocTest_Generic.GenericBase<U>", parameterType);
         }
+
+        [TestCase("UnsafeCombine", "delegate*<T1, T2, R>")]
+        [TestCase("UnsafeCombineOverload", "delegate*<System.IntPtr, System.UIntPtr, R>")]
+        public void Test_GetDocParameterType_CSharpFunctionPointer(string methodName, string expected)
+        {
+            var method = GetMethod(typeof(SampleClasses.FunctionPointers), methodName);
+
+            string parameterType = MDocUpdater.GetDocParameterType(method.Parameters[0].ParameterType);
+
+            Assert.AreEqual(expected, parameterType);
+        }
+
         [Test]
         public void Test_GetNamespace_IgnoredNamespaceGeneric()
         {
diff --git a/mdoc/mdoc.Test/SampleClasses/FunctionPointers.cs b/mdoc/mdoc.Test/SampleClasses/FunctionPointers.cs
new file mode 100644
index 00000000..9e84c0b8
--- /dev/null
+++ b/mdoc/mdoc.Test/SampleClasses/FunctionPointers.cs
@@ -0,0 +1,31 @@
+using System;
+
+namespace mdoc.Test.SampleClasses
+{
+    public class FunctionPointers
+    {
+        public unsafe static R UnsafeCombine<T1, T2, R>(delegate*<T1, T2, R> combinator, T1 left, T2 right) =>
+    combinator(left, right);
+
+        public unsafe static R UnsafeCombineOverload<R>(delegate*<IntPtr, UIntPtr, R> combinator, IntPtr left, UIntPtr right) =>
+combinator(left, right);
+
+        public unsafe static R UnsafeCombine1<T1, T2, R>(delegate* unmanaged[Cdecl]<T1, T2, R> combinator, T1 left, T2 right) =>
+            combinator(left, right);
+
+        public unsafe static R UnsafeCombine2<T1, T2, T3, R>(delegate* unmanaged[Stdcall]<ref T1, in T2, out T3, R> combinator, T1 left, T2 right, T3 outVar) =>
+    combinator(ref left, right, out outVar);
+
+        public unsafe static R UnsafeCombine3<T1, T2, R>(delegate* unmanaged[Fastcall]<T1, T2, ref R> combinator, T1 left, T2 right) =>
+    combinator(left, right);
+
+        public unsafe static R UnsafeCombine4<T1, T2, R>(delegate* unmanaged[Thiscall]<T1, T2, ref readonly R> combinator, T1 left, T2 right) =>
+combinator(left, right);
+
+        public unsafe static void UnsafeCombine5(delegate* unmanaged[Cdecl]<void> combinator) => combinator();
+
+        public unsafe static void UnsafeCombine6(delegate*<delegate* unmanaged[Fastcall]<string, int>, delegate*<string, int>> combinator) => combinator(null);
+
+        public unsafe static delegate*<delegate* unmanaged[Thiscall]<string, int>, delegate*<string, int>> UnsafeCombine7() => throw null;
+    }
+}
\ No newline at end of file
diff --git a/mdoc/mdoc.Test/mdoc.Test.csproj b/mdoc/mdoc.Test/mdoc.Test.csproj
index ae540c68..422b12fe 100644
--- a/mdoc/mdoc.Test/mdoc.Test.csproj
+++ b/mdoc/mdoc.Test/mdoc.Test.csproj
@@ -16,6 +16,7 @@
   </PropertyGroup>

   <PropertyGroup>

     <RunPostBuildEvent>Always</RunPostBuildEvent>

+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>

   </PropertyGroup>

   <ItemGroup>

     <Reference Include="mdoc.Test.Cplusplus, Version=1.0.6709.28740, Culture=neutral, processorArchitecture=x86">