xo-facet: typeseq strongly typed

include/xo/facet/facet.hpp

@@ -70,7 +70,7 @@ namespace xo {
                  "Abstract facet expected to have trivial dtor since no state");
             static_assert
                 (requires(T & facet) {
-                   { facet._typeseq() } -> std::convertible_to<std::int32_t>; },
+                    { facet._typeseq().seqno() } -> std::convertible_to<std::int32_t>; },
                     "Abstract facet must provide a _typeseq() method for safe downcasting");
             return true;
         };

include/xo/facet/typeseq.hpp

@@ -5,6 +5,7 @@
 
 #pragma once
 
+#include <iostream>
 #include <cstdint>
 
 namespace xo {
@@ -15,6 +16,8 @@ namespace xo {
          */
         template<typename Tag = class typeseq_tag>
         struct typeseq_impl {
+            explicit typeseq_impl(int32_t s) : seqno_{s} {}
+
             /** Can't have this be constexpr.
              *  We need ids in shared libraries to be generated
              *  at load time to avoid false positives
@@ -28,7 +31,7 @@ namespace xo {
              *  when using clang.
              **/
             template <typename T>
-            static int32_t id() {
+            static typeseq_impl<Tag> id() {
                 static bool armed = true;
                 static int32_t id = 0;
 
@@ -37,15 +40,40 @@ namespace xo {
                     id = ++s_next_id;
                 }
 
-                return id;
+                return typeseq_impl(id);
+
             }
 
+            int32_t seqno() const { return seqno_; }
+
+        private:
             static int32_t s_next_id;
+
+            int32_t seqno_;
         };
 
         template <typename Tag>
         int32_t typeseq_impl<Tag>::s_next_id = 0;
 
+        template <typename Tag>
+        inline bool
+        operator==(const typeseq_impl<Tag> & lhs, const typeseq_impl<Tag> & rhs) {
+            return lhs.seqno() == rhs.seqno();
+        }
+
+        template <typename Tag>
+        inline bool
+        operator!=(const typeseq_impl<Tag> & lhs, const typeseq_impl<Tag> & rhs) {
+            return lhs.seqno() != rhs.seqno();
+        }
+
+        template <typename Tag>
+        inline std::ostream &
+        operator<<(std::ostream & s, const typeseq_impl<Tag> & x) {
+            s << x.seqno();
+            return s;
+        }
+
         using typeseq = typeseq_impl<>;
     }
 } /*namespace xo*/

utest/objectmodel.test.cpp

@@ -34,7 +34,7 @@ namespace xo {
         using TypeErasedIface = struct IComplex_Any;
 
         /** RTTI: reports unique id# for actual runtime data representation **/
-        virtual int32_t _typeseq() const = 0;
+        virtual typeseq _typeseq() const = 0;
 
         virtual double xcoord(void * data) const = 0;
         virtual double ycoord(void * data) const = 0;
@@ -61,7 +61,7 @@ namespace xo {
 
         // from AComplex
 
-        virtual int32_t _typeseq() const final override { return s_typeseq; }
+        virtual typeseq _typeseq() const final override { return s_typeseq; }
 
         virtual double xcoord(void * data) const final override { return Impl::xcoord(*(DRepr*)data); }
         virtual double ycoord(void * data) const final override { return Impl::ycoord(*(DRepr*)data); }
@@ -70,12 +70,12 @@ namespace xo {
 
         virtual void destruct_data(void * data) const final override { Impl::destruct_data(*(DRepr*)data); }
 
-        static int32_t s_typeseq;
+        static typeseq s_typeseq;
         static bool _valid;
     };
 
     template <typename DRepr>
-    int32_t
+    typeseq
     IComplex_Xfer<DRepr>::s_typeseq = typeseq::id<DRepr>();
 
     template <typename DRepr>
@@ -96,7 +96,7 @@ namespace xo {
      *  such as IComplex_RectCoords or IComplex_PolarCoords.
      **/
     struct IComplex_Any : public AComplex {
-        virtual int32_t _typeseq() const final override { return s_typeseq; }
+        virtual typeseq _typeseq() const final override { return s_typeseq; }
 
         virtual double xcoord(void *) const final override { assert(false); return 0.0; }
         virtual double ycoord(void *) const final override { assert(false); return 0.0; }
@@ -105,11 +105,11 @@ namespace xo {
 
         virtual void destruct_data(void *) const final override { assert(false); }
 
-        static int32_t s_typeseq;
+        static typeseq s_typeseq;
         static bool _valid;
     };
 
-    int32_t
+    typeseq
     IComplex_Any::s_typeseq = typeseq::id<DVariantPlaceholder>();
 
     bool
@@ -190,7 +190,7 @@ namespace xo {
         RComplex() {}
         RComplex(Object::DataPtr data) : Object{std::move(data)} {}
 
-        int32_t _typeseq() const { return Object::iface()->_typeseq(); }
+        typeseq _typeseq() const { return Object::iface()->_typeseq(); }
         double xcoord() const { return Object::iface()->xcoord(Object::data()); }
         double ycoord() const { return Object::iface()->ycoord(Object::data()); }
         double argument() const { return Object::iface()->argument(Object::data()); }