Make interface types non c-style in Slang2026. (#7260)

* Make interface types non c-style.

* Make Optional<T> work with autodiff and existential types.

* Fix.

* patch behind slang 2026.

* Fix warnings.

* cleanup.

* Fix tests.

* Fix.

* Fix com interface lowering.

* Add comment to test.

* regenerate command line reference

* Add test for passing `none` to autodiff function.

* Fix recording of `getDynamicObjectRTTIBytes`.

* Fix nested Optional types.

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/source/slang/slang-ir-autodiff.cpp b/source/slang/slang-ir-autodiff.cpp
index c8dc3b480..133c257a8 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -1754,7 +1754,19 @@ IRType* DifferentiableTypeConformanceContext::differentiateType(
                     (UInt)diffTypeList.getCount(),
                     diffTypeList.getBuffer());
         }
-
+    case kIROp_OptionalType:
+        {
+            auto primalOptionalType = as<IROptionalType>(primalType);
+            if (auto diffElementType =
+                    differentiateType(builder, primalOptionalType->getValueType()))
+            {
+                return builder->getOptionalType(diffElementType);
+            }
+            else
+            {
+                return nullptr;
+            }
+        }
     default:
         return (IRType*)getDifferentialForType(builder, (IRType*)primalType);
     }