From 11fdc52d009565dddb674286647c6042d761d249 Mon Sep 17 00:00:00 2001
From: Marc Zwart <marcdevin@hotmail.com>
Date: Sun, 8 Feb 2026 22:03:20 +0100
Subject: [PATCH] WIP weaktable based function caching

---
 .../CSharp/CSharpTypeConversionRenderer.cs      | 17 ++++++++++++-----
 TypeShim/MarshallArgumentsTable.cs              | 14 ++++++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)
 create mode 100644 TypeShim/MarshallArgumentsTable.cs

diff --git a/TypeShim.Generator/CSharp/CSharpTypeConversionRenderer.cs b/TypeShim.Generator/CSharp/CSharpTypeConversionRenderer.cs
index 681d9873..2c8dbdbe 100644
--- a/TypeShim.Generator/CSharp/CSharpTypeConversionRenderer.cs
+++ b/TypeShim.Generator/CSharp/CSharpTypeConversionRenderer.cs
@@ -104,9 +104,9 @@ private void RenderInlineTypeDownConversion(InteropTypeInfo typeInfo, string acc
         {
             RenderInlineObjectTypeDownConversion(typeInfo, accessorExpressionRenderer);
         }
-        else if (typeInfo.IsDelegateType() && typeInfo.ArgumentInfo is DelegateArgumentInfo argumentInfo) // Action/Action<T1...Tn>/Func<T1...Tn>
+        else if (typeInfo.IsDelegateType()) // Action/Action<T1...Tn>/Func<T1...Tn>
         {
-            RenderInlineDelegateTypeDownConversion(argumentInfo, accessorName, accessorExpressionRenderer);
+            RenderInlineDelegateTypeDownConversion(typeInfo, accessorName, accessorExpressionRenderer);
         }
         else
         {
@@ -226,9 +226,13 @@ private string RenderNullableTaskTypeConversion(InteropTypeInfo targetNullableTa
         return $"{tcsVarName}?.Task";
     }
 
-    private void RenderInlineDelegateTypeDownConversion(DelegateArgumentInfo argumentInfo, string accessorName, DeferredExpressionRenderer accessorExpressionRenderer)
+    private void RenderInlineDelegateTypeDownConversion(InteropTypeInfo typeInfo, string accessorName, DeferredExpressionRenderer accessorExpressionRenderer)
     {
-        _ctx.Append('(');
+        DelegateArgumentInfo argumentInfo = typeInfo.ArgumentInfo ?? throw new InvalidOperationException("Delegate type is missing argumentinfo.");
+        _ctx.Append("MarshallArgumentsTable.GetOrCreate<").Append(typeInfo.CSharpTypeSyntax).Append(">(");
+        accessorExpressionRenderer.Render();
+        _ctx.Append(", () => ")
+            .Append('(');
         for (int i = 0; i < argumentInfo.ParameterTypes.Length; i++)
         {
             if (i > 0) _ctx.Append(", ");
@@ -257,11 +261,13 @@ private void RenderInlineDelegateTypeDownConversion(DelegateArgumentInfo argumen
         {
             invocationExpressionRenderer.Render();
         }
+        _ctx.Append(')');
     }
 
     private void RenderInlineDelegateTypeUpConversion(InteropTypeInfo typeInfo, string varName, DelegateArgumentInfo argumentInfo)
     {
-        _ctx.Append('(');
+        _ctx.Append("MarshallArgumentsTable.GetOrCreate<").Append(typeInfo.CSharpInteropTypeSyntax).Append(">(").Append(varName).Append(", () => ")
+            .Append('(');
         for (int i = 0; i < argumentInfo.ParameterTypes.Length; i++)
         {
             if (i > 0)
@@ -299,5 +305,6 @@ private void RenderInlineDelegateTypeUpConversion(InteropTypeInfo typeInfo, stri
         {
             invocationExpressionRenderer.Render();
         }
+        _ctx.Append(')');
     }
 }
\ No newline at end of file
diff --git a/TypeShim/MarshallArgumentsTable.cs b/TypeShim/MarshallArgumentsTable.cs
new file mode 100644
index 00000000..cc93dd2c
--- /dev/null
+++ b/TypeShim/MarshallArgumentsTable.cs
@@ -0,0 +1,14 @@
+using System.Runtime.CompilerServices;
+
+namespace TypeShim;
+
+public static class MarshallArgumentsTable
+{
+    private static readonly ConditionalWeakTable<Type, ConditionalWeakTable<object, object>> _typeTables = new();
+
+    public static T GetOrCreate<T>(object target, Func<T> factory) where T : class
+    {
+        ConditionalWeakTable<object, object> table = _typeTables.GetValue(typeof(T), _ => new ConditionalWeakTable<object, object>());
+        return (T)table.GetValue(target, _ => factory()!);
+    }
+}
\ No newline at end of file