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, 12 insertions, 1 deletions

diff --git a/source/slang/slang-ast-type.h b/source/slang/slang-ast-type.h
index 50d523cc5..3c50b1899 100644
--- a/source/slang/slang-ast-type.h
+++ b/source/slang/slang-ast-type.h
@@ -552,12 +552,23 @@ class InOutType : public OutTypeBase
     SLANG_AST_CLASS(InOutType)
 };
 
+class RefTypeBase : public ParamDirectionType
+{
+    SLANG_AST_CLASS(RefTypeBase)
+};
+
 // The type for an `ref` parameter, e.g., `ref T`
-class RefType : public ParamDirectionType
+class RefType : public RefTypeBase
 {
     SLANG_AST_CLASS(RefType)
 };
 
+// The type for an `constref` parameter, e.g., `constref T`
+class ConstRefType : public RefTypeBase
+{
+    SLANG_AST_CLASS(ConstRefType)
+};
+
 class OptionalType : public BuiltinType
 {
     SLANG_AST_CLASS(OptionalType)