Add partial ref param support

Author: josetr

src/AST/Assembly.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("CppSharp.Generator")]

src/AST/TypeExtensions.cs

@@ -442,5 +442,31 @@ public static long GetSizeInBits(this ArrayType array)
         {
             return array.Size * array.ElementSize;
         }
+
+        internal static bool IsReferenceToPtrToClass(this Type type)
+        {
+            var @ref = type.Desugar().AsLvReference();
+            if (@ref == null)
+                return false;
+
+            var @ptr = @ref.Pointee.Desugar(false).AsPtr();
+            if (@ptr == null)
+                return false;
+
+            var @class = @ptr.Pointee;
+            return @class != null && @class.IsClass();
+        }
+
+        internal static PointerType AsLvReference(this Type type)
+        {
+            var reference = type as PointerType;
+            return reference?.Modifier == PointerType.TypeModifier.LVReference ? reference : null;
+        }
+
+        internal static PointerType AsPtr(this Type type)
+        {
+            var ptr = type as PointerType;
+            return ptr?.Modifier == PointerType.TypeModifier.Pointer ? ptr : null;
+        }
     }
 }

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -3193,6 +3193,17 @@ public void GenerateFunctionCall(string functionName, Function function,
             }
             WriteLine("{0}({1});", functionName, string.Join(", ", names));
 
+            foreach(var param in @params)
+            {
+                if (param.Param.IsInOut && param.Param.Type.IsReferenceToPtrToClass())
+                {
+                    var qualifiedClass = param.Param.Type.Visit(TypePrinter);
+                    
+                    WriteLine($"if ({param.Name} != {param.Param.Name}.__Instance)");
+                    WriteLine($"{param.Param.Name} = {qualifiedClass}.__GetOrCreateInstance(__{param.Name}, false);");
+                }
+            }
+
             foreach (TextGenerator cleanup in from p in @params
                                               select p.Context.Cleanup)
                 Write(cleanup);

tests/CSharp/CSharp.Tests.cs

@@ -1908,4 +1908,21 @@ public void TestFunctionTemplate()
         Assert.That(CSharpTemplates.FunctionTemplate(6f), Is.EqualTo(6 + 4.1f));
         Assert.That(CSharpTemplates.FunctionTemplate(7), Is.EqualTo(7 + 4));
     }
+
+    [Test]
+    public void TestPatialRefSupport()
+    {
+        var myclass = new ClassWithIntValue();
+        var backup = myclass;
+        myclass.Value = 7;
+
+        CSharp.CSharp.ModifyCore(ref myclass);
+        Assert.That(myclass.Value, Is.EqualTo(10));
+        Assert.That(myclass, Is.SameAs(myclass));
+
+        CSharp.CSharp.CreateCore(ref myclass);
+        Assert.That(myclass.Value, Is.EqualTo(20));
+        Assert.That(myclass, Is.Not.SameAs(backup));
+    }
+
 }

tests/CSharp/CSharp.h

@@ -1535,4 +1535,19 @@ DLL_API int TestFunctionToInstanceMethodRefStruct(FTIStruct* bb, FTIStruct& defa
 DLL_API int TestFunctionToInstanceMethodConstStruct(FTIStruct* bb, const FTIStruct defaultValue);
 DLL_API int TestFunctionToInstanceMethodConstRefStruct(FTIStruct* bb, const FTIStruct& defaultValue);
 
-class ClassWithoutNativeToManaged { };
+class ClassWithoutNativeToManaged { };
+
+struct DLL_API ClassWithIntValue {
+    int value;
+};
+
+DLL_API inline ClassWithIntValue* ModifyCore(CS_IN_OUT ClassWithIntValue*& pClass) {
+    pClass->value = 10;
+    return nullptr;
+}
+
+DLL_API inline ClassWithIntValue* CreateCore(CS_IN_OUT ClassWithIntValue*& pClass) {
+    pClass = new ClassWithIntValue();
+    pClass->value = 20;
+    return nullptr;
+}