Support `constref` parameters passing. (#3249)

* Support `constref` parameters passing.

* Fix.

* Fix.

* Add test and diagnostic on mix use of __constref and no_diff.

* check for [constref] on differentiable member method.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/source/slang/slang-ast-type.cpp b/source/slang/slang-ast-type.cpp
index f80de86fd..a29ff9bb3 100644
--- a/source/slang/slang-ast-type.cpp
+++ b/source/slang/slang-ast-type.cpp
@@ -372,6 +372,10 @@ ParameterDirection FuncType::getParamDirection(Index index)
     {
         return kParameterDirection_Ref;
     }
+    else if (as<ConstRefType>(paramType))
+    {
+        return kParameterDirection_ConstRef;
+    }
     else if (as<InOutType>(paramType))
     {
         return kParameterDirection_InOut;