From 26b9a176e08ec6918d6fdebe1d7b586336f6f0fd Mon Sep 17 00:00:00 2001
From: aidanfnv <aidanf@nvidia.com>
Date: Wed, 23 Jul 2025 18:42:24 -0700
Subject: Skip creating transitive witnesses for interface conformances that
 are inherited through structs (#7597)

* Eliminate null-pointer reference in multilevel struct interface inheritance

* Add test

* Replace witness nullptr guard with conformance check to skip the witness

* Update test

* Skip creating transitive witness entirely for struct-struct-interface

* format code (#14)

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

* Removes casts, check for identity witness

---------

Co-authored-by: slangbot <ellieh+slangbot@nvidia.com>
Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>
---
 .../generic/multilevel-inheritance.slang           | 31 ++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 tests/experiments/generic/multilevel-inheritance.slang

(limited to 'tests/experiments')

diff --git a/tests/experiments/generic/multilevel-inheritance.slang b/tests/experiments/generic/multilevel-inheritance.slang
new file mode 100644
index 000000000..f3db67d70
--- /dev/null
+++ b/tests/experiments/generic/multilevel-inheritance.slang
@@ -0,0 +1,31 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -gnone -std 2026
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -gminimal -std 2026
+//TEST:SIMPLE(filecheck=CHECK_LEGACY): -target spirv -gnone -std 2025
+//TEST:SIMPLE(filecheck=CHECK_LEGACY): -target spirv -gminimal -std 2025
+//TEST:SIMPLE(filecheck=CHECK_LEGACY): -target spirv -gnone -std legacy
+//TEST:SIMPLE(filecheck=CHECK_LEGACY): -target spirv -gminimal -std legacy
+
+// CHECK: error 30811
+// CHECK: struct Child : Parent {};
+// CHECK: error 38029
+// CHECK: getObject<Child>();
+
+// CHECK_LEGACY: warning 30816
+// CHECK_LEGACY: struct Child : Parent {};
+// CHECK_LEGACY: error 38029
+// CHECK_LEGACY: getObject<Child>();
+
+interface IFoo {};
+struct Parent : IFoo {};
+struct Child : Parent {};
+
+T getObject<T>() where T : IFoo
+{
+    return T();
+}
+
+[shader("compute")]
+void main()
+{
+    getObject<Child>();
+}
-- 
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