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, 17 insertions, 0 deletions

diff --git a/source/slang/slang-ir-lower-existential.cpp b/source/slang/slang-ir-lower-existential.cpp
index c4ee6e6fc..076ed57bd 100644
--- a/source/slang/slang-ir-lower-existential.cpp
+++ b/source/slang/slang-ir-lower-existential.cpp
@@ -131,6 +131,19 @@ struct ExistentialLoweringContext
         processExtractExistentialElement(inst, 2);
     }
 
+    void processIsNullExistential(IRIsNullExistential* inst)
+    {
+        IRBuilder builder(sharedContext->module);
+        builder.setInsertBefore(inst);
+
+        auto rttiElement = extractTupleElement(&builder, inst->getOperand(0), 0);
+        auto isNull = builder.emitNeq(
+            builder.emitGetElement(builder.getUIntType(), rttiElement, 0),
+            builder.getIntValue(builder.getUIntType(), 0));
+        inst->replaceUsesWith(isNull);
+        inst->removeAndDeallocate();
+    }
+
     void processExtractExistentialWitnessTable(IRExtractExistentialWitnessTable* inst)
     {
         processExtractExistentialElement(inst, 1);
@@ -261,6 +274,10 @@ struct ExistentialLoweringContext
         {
             processExtractExistentialWitnessTable(extractExistentialWitnessTable);
         }
+        else if (auto isNullExistential = as<IRIsNullExistential>(inst))
+        {
+            processIsNullExistential(isNullExistential);
+        }
     }
 
     void processModule()