Special case STGMEDIUM field unmaaged type detection

Author: kant2002

WinFormsComInterop.SourceGenerator/Generator.cs

@@ -390,6 +390,20 @@ private static void GenerateBlittableStructWrapper(IndentedStringBuilder source,
                 source.AppendLine("}");
                 return;
             }
+
+            if (type.ToDisplayString() == "System.Runtime.InteropServices.ComTypes.STGMEDIUM")
+            {
+                source.AppendLine($"struct {type.Name}_native");
+                source.AppendLine("{");
+                source.PushIndent();
+                source.AppendLine($"public System.Runtime.InteropServices.ComTypes.TYMED tymed;");
+                source.AppendLine($"public System.IntPtr unionmember;");
+                source.AppendLine($"public System.IntPtr pUnkForRelease;");
+                source.PopIndent();
+                source.AppendLine("}");
+                return;
+            }
+
             source.AppendLine($"struct {type.Name}_native");
             source.AppendLine("{");
             source.PushIndent();

WinFormsComInterop.SourceGenerator/MethodGenerationContext.cs

@@ -122,9 +122,15 @@ public Marshaller CreateElementMarshaller(IArrayTypeSymbol arrayTypeSymbol, stri
             return marshaller;
         }
 
-        public Marshaller CreateFieldMarshaller(IFieldSymbol fieldSymbol, string prefix, int index)
+        public Marshaller CreateFieldMarshaller(IFieldSymbol fieldSymbol, ITypeSymbol parentType, string prefix, int index)
         {
-            Marshaller marshaller = CreateMarshaller(fieldSymbol.Type, null);
+            UnmanagedType? unmanagedType = GetMarshalAs(fieldSymbol.GetAttributes()).UnmanagedType;
+            if (parentType.ToDisplayString() == "System.Runtime.InteropServices.ComTypes.STGMEDIUM" && fieldSymbol.Name == "pUnkForRelease")
+            {
+                unmanagedType = UnmanagedType.IUnknown;
+            }
+
+            Marshaller marshaller = CreateMarshaller(fieldSymbol.Type, unmanagedType);
             marshaller.Name = prefix + "_" + fieldSymbol.Name;
             marshaller.Type = fieldSymbol.Type;
             marshaller.RefKind = RefKind.Ref;

WinFormsComInterop.SourceGenerator/StructMarshaller.cs

@@ -25,7 +25,7 @@ public override void ConvertToUnmanagedParameter(IndentedStringBuilder builder)
                         continue;
                     }
 
-                    var marshaller = Context.CreateFieldMarshaller(fieldSymbol, LocalVariable, i);
+                    var marshaller = Context.CreateFieldMarshaller(fieldSymbol, Type, LocalVariable, i);
                     builder.AppendLine($"var {marshaller.Name} = {Name}.{fieldSymbol.Name};");
                     marshaller.ConvertToUnmanagedParameter(builder);
                     builder.AppendLine($"{LocalVariable}.{fieldSymbol.Name} = {marshaller.LocalVariable};");
@@ -77,7 +77,7 @@ public override void MarshalOutputParameter(IndentedStringBuilder builder)
                         continue;
                     }
 
-                    var marshaller = Context.CreateFieldMarshaller(fieldSymbol, LocalVariable, i);
+                    var marshaller = Context.CreateFieldMarshaller(fieldSymbol, Type, LocalVariable, i);
                     builder.AppendLine($"var {marshaller.Name} = {LocalVariable}.{fieldSymbol.Name};");
                     marshaller.ConvertToUnmanagedParameter(builder);
                     if (MethodGenerationContext.IsBlittableType(fieldSymbol.Type))