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, 5 insertions, 4 deletions

diff --git a/source/slang/slang-check-conversion.cpp b/source/slang/slang-check-conversion.cpp
index c4efba658..c2cfabcfe 100644
--- a/source/slang/slang-check-conversion.cpp
+++ b/source/slang/slang-check-conversion.cpp
@@ -991,11 +991,12 @@ namespace Slang
             return true;
         }
 
-        if (auto refType = as<RefType>(toType))
+        if (auto refType = as<RefTypeBase>(toType))
         {
-            if (!refType->getValueType()->equals(fromType))
+            ConversionCost cost;
+            if (!canCoerce(refType->getValueType(), fromType, fromExpr, &cost))
                 return false;
-            if (!fromExpr->type.isLeftValue)
+            if (as<RefType>(toType) && !fromExpr->type.isLeftValue)
                 return false;
             
             ConversionCost subCost = kConversionCost_GetRef;
@@ -1016,7 +1017,7 @@ namespace Slang
 
 
         // Allow implicit dereferencing a reference type.
-        if (auto fromRefType = as<RefType>(fromType))
+        if (auto fromRefType = as<RefTypeBase>(fromType))
         {
             auto fromValueType = fromRefType->getValueType();