Provide more information in Desc structures

sources/ClangSharp.PInvokeGenerator/Abstractions/FunctionOrDelegateDesc.cs

@@ -13,6 +13,7 @@ internal struct FunctionOrDelegateDesc<TCustomAttrGeneratorData>
         public string EscapedName { get; set; }
         public string EntryPoint { get; set; }
         public string LibraryPath { get; set; }
+        public string ReturnType { get; set; }
         public CallingConvention CallingConvention { get; set; }
         public FunctionOrDelegateFlags Flags { get; set; }
         public long? VtblIndex { get; set; }
@@ -197,6 +198,22 @@ public bool? IsStatic
             }
         }
 
+        public bool NeedsReturnFixup
+        {
+            get => (Flags & FunctionOrDelegateFlags.NeedsReturnFixup) != 0;
+            set => Flags = value
+                ? Flags | FunctionOrDelegateFlags.NeedsReturnFixup
+                : Flags & ~FunctionOrDelegateFlags.NeedsReturnFixup;
+        }
+
+        public bool IsCxxConstructor
+        {
+            get => (Flags & FunctionOrDelegateFlags.IsCxxConstructor) != 0;
+            set => Flags = value
+                ? Flags | FunctionOrDelegateFlags.IsCxxConstructor
+                : Flags & ~FunctionOrDelegateFlags.IsCxxConstructor;
+        }
+
         public Action<TCustomAttrGeneratorData> WriteCustomAttrs { get; set; }
         public TCustomAttrGeneratorData CustomAttrGeneratorData { get; set; }
     }

sources/ClangSharp.PInvokeGenerator/Abstractions/IOutputBuilder.VisitDecl.cs

@@ -31,7 +31,6 @@ internal partial interface IOutputBuilder
 
         void BeginFunctionOrDelegate<TCustomAttrGeneratorData>(in FunctionOrDelegateDesc<TCustomAttrGeneratorData> info,
             ref bool isMethodClassUnsafe);
-        void WriteReturnType(string typeString);
         void BeginFunctionInnerPrototype(string escapedName);
         void BeginParameter<TCustomAttrGeneratorData>(in ParameterDesc<TCustomAttrGeneratorData> info);
         void BeginParameterDefault();

sources/ClangSharp.PInvokeGenerator/Abstractions/StructDesc.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft and Contributors. All rights reserved. Licensed under the University of Illinois/NCSA Open Source License. See LICENSE.txt in the project root for license information.
 
 using System;
+using System.Diagnostics;
 using System.Runtime.InteropServices;
 using ClangSharp.Interop;
 
@@ -12,7 +13,7 @@ internal struct StructDesc<TCustomAttrGeneratorData>
         public string EscapedName { get; set; }
         public string NativeType { get; set; }
         public string NativeInheritance { get; set; }
-        public StructLayoutAttribute Layout { get; set; }
+        public LayoutDesc Layout { get; set; }
         public Guid? Uuid { get; set; }
         public StructFlags Flags { get; set; }
         public CXSourceLocation? Location { get; set; }
@@ -43,7 +44,53 @@ public bool HasVtbl
             }
         }
 
+        public bool IsUnion
+        {
+            get => (Flags & StructFlags.IsUnion) != 0;
+            set => Flags = value ? Flags | StructFlags.IsUnion : Flags & ~StructFlags.IsUnion;
+        }
+
         public Action<TCustomAttrGeneratorData> WriteCustomAttrs { get; set; }
         public TCustomAttrGeneratorData CustomAttrGeneratorData { get; set; }
+
+        public StructLayoutAttribute LayoutAttribute
+        {
+            get
+            {
+                var layout = Layout;
+
+                if (IsUnion)
+                {
+                    Debug.Assert(layout.Kind == LayoutKind.Explicit);
+
+                    StructLayoutAttribute attribute = new(layout.Kind);
+
+                    if (layout.Pack < layout.MaxFieldAlignment)
+                    {
+                        attribute.Pack = (int)layout.Pack;
+                    }
+
+                    return attribute;
+                }
+
+                if (layout.Pack < layout.MaxFieldAlignment)
+                {
+                    return new StructLayoutAttribute(layout.Kind) {Pack = (int)layout.Pack};
+                }
+
+                return null;
+            }
+        }
+
+        public struct LayoutDesc
+        {
+            public long Alignment32 { get; set; }
+            public long Alignment64 { get; set; }
+            public long Size32 { get; set; }
+            public long Size64 { get; set; }
+            public long Pack { get; set; }
+            public long MaxFieldAlignment { get; set; }
+            public LayoutKind Kind { get; set; }
+        }
     }
 }

sources/ClangSharp.PInvokeGenerator/Abstractions/StructFlags.cs

@@ -8,6 +8,7 @@ namespace ClangSharp.Abstractions
     public enum StructFlags
     {
         IsUnsafe = 1 << 0,
-        HasVtbl = 1 << 1
+        HasVtbl = 1 << 1,
+        IsUnion = 1 << 2,
     }
 }

sources/ClangSharp.PInvokeGenerator/CSharp/CSharpOutputBuilder.VisitDecl.cs

@@ -279,6 +279,12 @@ public void BeginFunctionOrDelegate<TCustomAttrGeneratorData>(in FunctionOrDeleg
                     }
                 }
             }
+
+            if (!desc.IsCxxConstructor)
+            {
+                Write(desc.ReturnType);
+                Write(' ');
+            }
         }
 
         private void WriteSourceLocation(CXSourceLocation location, bool inline)
@@ -304,12 +310,6 @@ private void WriteSourceLocation(CXSourceLocation location, bool inline)
                 Write(' ');
         }
 
-        public void WriteReturnType(string typeString)
-        {
-            Write(typeString);
-            Write(' ');
-        }
-
         public void BeginFunctionInnerPrototype(string escapedName)
         {
             Write(escapedName);
@@ -433,15 +433,15 @@ public void EndFunctionOrDelegate(bool isVirtual, bool isBodyless)
 
         public void BeginStruct<TCustomAttrGeneratorData>(in StructDesc<TCustomAttrGeneratorData> info)
         {
-            if (info.Layout is not null)
+            if (info.LayoutAttribute is { } attribute)
             {
                 AddUsingDirective("System.Runtime.InteropServices");
                 WriteIndented("[StructLayout(LayoutKind.");
-                Write(info.Layout.Value);
-                if (info.Layout.Pack != default)
+                Write(attribute.Value);
+                if (attribute.Pack != default)
                 {
                     Write(", Pack = ");
-                    Write(info.Layout.Pack);
+                    Write(attribute.Pack);
                 }
 
                 WriteLine(")]");

sources/ClangSharp.PInvokeGenerator/FunctionOrDelegateFlags.cs

@@ -17,6 +17,8 @@ public enum FunctionOrDelegateFlags
         IsCxxRecordCtxUnsafe = 1 << 9,
         IsMemberFunction = 1 << 10,
         IsStatic = 1 << 11,
-        IsNotStatic = 1 << 12
+        IsNotStatic = 1 << 12,
+        NeedsReturnFixup = 1 << 13,
+        IsCxxConstructor = 1 << 14,
     }
 }