fix ast-lowering of `TransitiveSubtypeWitness` values.

1 files changed, 3 insertions, 0 deletions

diff --git a/source/slang/ast-legalize.cpp b/source/slang/ast-legalize.cpp
index 98a9c2573..4f17369f2 100644
--- a/source/slang/ast-legalize.cpp
+++ b/source/slang/ast-legalize.cpp
@@ -2623,6 +2623,9 @@ struct LoweringVisitor
         if (auto litVal = dynamic_cast<ConstantIntVal*>(val))
             return val;
 
+        // We do not use subtype witness for ast lowering, return it unchanged.
+        if (auto subtypeWitnessVal = dynamic_cast<SubtypeWitness*>(val))
+            return val;
         SLANG_UNEXPECTED("unhandled value kind");
     }