[orc-rt] Prevent RTTIExtends from being used for errors. (#172250)

Custom error types (ErrorInfoBase subclasses) should use ErrorExtends as
of 8f51da3. Adding a static_assert allows us to enforce that at
compile-time.

Author: lhames

orc-rt/include/orc-rt/RTTI.h

@@ -52,8 +52,12 @@
 #ifndef ORC_RT_RTTI_H
 #define ORC_RT_RTTI_H
 
+#include <type_traits>
+
 namespace orc_rt {
 
+class ErrorInfoBase;
+
 template <typename ThisT, typename ParentT> class RTTIExtends;
 
 /// Base class for the extensible RTTI hierarchy.
@@ -107,6 +111,10 @@ class RTTIRoot {
 ///
 template <typename ThisT, typename ParentT> class RTTIExtends : public ParentT {
 public:
+  static_assert(!std::is_base_of_v<ErrorInfoBase, ParentT>,
+                "RTTIExtends should not be used to define orc_rt custom error "
+                "types, use ErrorExtends instead");
+
   // Inherit constructors and isA methods from ParentT.
   using ParentT::isA;
   using ParentT::ParentT;