Variadic Generics Part 2: IR lowering and specialization. (#4849)

* Variadic Generics Part 2: IR lowering and specialization.

* Update design doc status.

* Update design doc.

* Resolve review comments.

1 files changed, 13 insertions, 1 deletions

diff --git a/source/slang/slang-ast-builder.cpp b/source/slang/slang-ast-builder.cpp
index faf15470f..3a2b2933d 100644
--- a/source/slang/slang-ast-builder.cpp
+++ b/source/slang/slang-ast-builder.cpp
@@ -525,7 +525,19 @@ FuncType* ASTBuilder::getFuncType(ArrayView<Type*> parameters, Type* result, Typ
 
 TupleType* ASTBuilder::getTupleType(List<Type*>& types)
 {
-    return getOrCreate<TupleType>(types.getArrayView());
+    // The canonical form of a tuple type is always a DeclRefType(GenAppDeclRef(TupleDecl, ConcreteTypePack(types...))).
+    // If `types` is already a single ConcreteTypePack, then we can use that directly.
+    if (types.getCount() == 1)
+    {
+        if (isTypePack(types[0]))
+        {
+            return as<TupleType>(getSpecializedBuiltinType(types[0], "TupleType"));
+        }
+    }
+
+    // Otherwise, we need to create a ConcreteTypePack to hold the types.
+    auto typePack = getTypePack(types.getArrayView());
+    return as<TupleType>(getSpecializedBuiltinType(typePack, "TupleType"));
 }
 
 TypeType* ASTBuilder::getTypeType(Type* type)