strongdef: don't expose the raw data directly

strongdef.cpp

@@ -13,4 +13,4 @@
 // This instantiation is not meant to be exported, only being used as a local
 // compilation error canary.
 
-template struct cruft::strongdef::index<void,unsigned>;
+template class cruft::strongdef::index<void,unsigned>;

strongdef.hpp

@@ -20,7 +20,8 @@ namespace cruft::strongdef {
     /// A transparent wrapper around a (typically lightweight) type for the
     /// purposes of overload disambiguation. It acts like a typesafe typedef.
     template <typename TagT, typename T = typename TagT::index_type>
-    struct index {
+    class index {
+    public:
         using value_type = T;
         using tag_type   = TagT;
 
@@ -59,7 +60,14 @@ namespace cruft::strongdef {
 
         constexpr auto& operator++ (void)& { ++data; return *this; }
 
-        T data;
+        constexpr T      * operator-> ()        &{ return &data; }
+        constexpr T const* operator-> ()  const &{ return &data; }
+
+        constexpr T      & operator*  ()        &{ return  data; }
+        constexpr T const& operator*  ()  const &{ return  data; }
+
+    private:
+        value_type data;
     };
 
 
@@ -67,7 +75,7 @@ namespace cruft::strongdef {
     std::ostream&
     operator<< (std::ostream &os, index<TagT,T> const &val)
     {
-        return os << +val.data;
+        return os << +*val;
     }
 }
 
@@ -89,7 +97,7 @@ static auto indices (ContainerT const &obj)
 
             iterator& operator++ ()
             {
-                ++idx.data;
+                ++idx;
                 return *this;
             }
 

test/strongdef.cpp

@@ -10,15 +10,8 @@ main (void)
 
     // These tests are less about functional testing, and more about link testing.
     cruft::strongdef::index<void,unsigned> fortytwo (42u);
-    tap.expect_eq (fortytwo.data, 42u, "raw data equality");
-    tap.expect_eq (fortytwo,      decltype(fortytwo) (42u), "passthrough equality");
-
-#if 0
-    // Ensure numeric_limits has been specialised. Unknown types are default initialised, so check if we get non-zero for maximum.
-    tap.expect_eq (std::numeric_limits<decltype(fortytwo)>::max (),
-                   std::numeric_limits<decltype(fortytwo)::value_type>::max (),
-                   "numeric_limits has been specialised");
-#endif
+    tap.expect_eq (*fortytwo, 42u, "raw data equality");
+    tap.expect_eq ( fortytwo, decltype(fortytwo) (42u), "passthrough equality");
 
     return tap.status ();
 }