\end{itemize}
\begin{code}
-mkTupleTy :: Boxity -> Int -> [Type] -> Type
-mkTupleTy boxity arity tys = mkTyConApp (tupleTyCon boxity arity) tys
+mkTupleTy :: Boxity -> [Type] -> Type
+-- Special case for *boxed* 1-tuples, which are represented by the type itself
+mkTupleTy boxity [ty] | Boxed <- boxity = ty
+mkTupleTy boxity tys = mkTyConApp (tupleTyCon boxity (length tys)) tys
unitTy :: Type
-unitTy = mkTupleTy Boxed 0 []
+unitTy = mkTupleTy Boxed []
\end{code}
%************************************************************************