Fix the generated C# for const char*&

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Generators/CSharp/CSharpMarshal.cs

@@ -499,7 +499,7 @@ namespace CppSharp.Generators.CSharp
             var isRefParam = param != null && (param.IsInOut || param.IsOut);
 
             var pointee = pointer.Pointee.Desugar();
-            if (pointee.IsConstCharString() && isRefParam)
+            if (pointee.IsConstCharString())
             {
                 if (param.IsOut)
                 {
@@ -513,13 +513,16 @@ namespace CppSharp.Generators.CSharp
                     MarshalString(pointee);
                     pointer.QualifiedPointee.Visit(this);
                     Context.ArgumentPrefix.Write("&");
+                    return true;
                 }
-                else
+                if (pointer.IsReference)
                 {
+                    Context.Return.Write($@"({typePrinter.PrintNative(
+                        pointee.GetQualifiedPointee())}*) ");
                     pointer.QualifiedPointee.Visit(this);
-                    Context.Cleanup.WriteLine($"Marshal.FreeHGlobal({Context.ArgName});");
+                    Context.ArgumentPrefix.Write("&");
+                    return true;
                 }
-                return true;
             }
 
             var finalPointee = (pointee.GetFinalPointee() ?? pointee).Desugar();

src/Generator/Types/Std/Stdlib.cs

@@ -168,6 +168,7 @@ namespace CppSharp.Types.Std
         public override void CSharpMarshalToNative(CSharpMarshalContext ctx)
         {
             if (ctx.Parameter.Usage == ParameterUsage.Unknown &&
+                !ctx.Parameter.Type.IsReference() &&
                 ctx.MarshalKind != MarshalKind.NativeField &&
                 ctx.MarshalKind != MarshalKind.VTableReturnValue &&
                 ctx.MarshalKind != MarshalKind.Variable)

tests/CSharp/CSharp.Tests.cs

@@ -1255,6 +1255,12 @@ public unsafe class CSharpTests : GeneratorTestFixture
         }
     }
 
+    [Test]
+    public void TestConstCharStarRef()
+    {
+        Assert.That(CSharp.CSharp.TakeConstCharStarRef("Test"), Is.EqualTo("Test"));
+    }
+
     public class Inter : SimpleInterface
     {
         public override int Size => s;

tests/CSharp/CSharp.cpp

@@ -1551,3 +1551,8 @@ char* returnCharPointer()
 {
     return 0;
 }
+
+const char* takeConstCharStarRef(const char*& c)
+{
+    return c;
+}

tests/CSharp/CSharp.cs

@@ -259,7 +259,8 @@ namespace CppSharp.Tests
 
         public override void CSharpMarshalToNative(CSharpMarshalContext ctx)
         {
-            ctx.Return.Write("\"test\"");
+            ctx.Return.Write(ctx.Parameter.Type.Desugar().IsAddress() ?
+                "global::System.IntPtr.Zero" : "\"test\"");
         }
 
         public override void CSharpMarshalToManaged(CSharpMarshalContext ctx)

tests/CSharp/CSharp.h

@@ -1297,3 +1297,4 @@ private:
 
 DLL_API void va_listFunction(va_list v);
 DLL_API char* returnCharPointer();
+DLL_API const char* takeConstCharStarRef(const char*& c);