use whitelist filter on std::hash<> to avoid bad static_assert in multiple std lib implementations

3 files changed, 32 insertions, 16 deletions

diff --git a/Rx/v2/src/rxcpp/operators/rx-distinct.hpp b/Rx/v2/src/rxcpp/operators/rx-distinct.hpp
index c2994ca..784c940 100644
--- a/Rx/v2/src/rxcpp/operators/rx-distinct.hpp
+++ b/Rx/v2/src/rxcpp/operators/rx-distinct.hpp
@@ -29,7 +29,7 @@ struct distinct<T, typename std::enable_if<is_hashable<T>::value>::type>
         typedef rxu::decay_t<Subscriber> dest_type;
         typedef observer<value_type, this_type> observer_type;
         dest_type dest;
-        mutable std::unordered_set<source_value_type> remembered;
+        mutable std::unordered_set<source_value_type, rxcpp::filtered_hash<source_value_type>> remembered;
 
         distinct_observer(dest_type d)
                 : dest(d)
diff --git a/Rx/v2/src/rxcpp/rx-predef.hpp b/Rx/v2/src/rxcpp/rx-predef.hpp
index c4f27a6..6d1a394 100644
--- a/Rx/v2/src/rxcpp/rx-predef.hpp
+++ b/Rx/v2/src/rxcpp/rx-predef.hpp
@@ -261,21 +261,6 @@ struct identity_for
     }
 };
 
-template<typename, typename = void>
-struct is_hashable
-        : std::false_type {};
-
-template<typename T>
-struct is_hashable<T, typename std::enable_if<!!sizeof(std::declval<std::hash<T>>()(std::declval<T>()))>::type>
-        : std::true_type {};
-
-}
-
-// disable std::hash for observable<>
-namespace std {
-    template <class T, class Source> struct hash<rxcpp::observable<T, Source>>;
-    template <class T, class Source> struct hash<rxcpp::connectable_observable<T, Source>>;
-    template <class K, class T, class Source> struct hash<rxcpp::grouped_observable<K, T, Source>>;
 }
 
 #endif
diff --git a/Rx/v2/src/rxcpp/rx-util.hpp b/Rx/v2/src/rxcpp/rx-util.hpp
index 8b87175..cbc4956 100644
--- a/Rx/v2/src/rxcpp/rx-util.hpp
+++ b/Rx/v2/src/rxcpp/rx-util.hpp
@@ -677,6 +677,37 @@ public:
 }
 namespace rxu=util;
 
+//
+// due to an noisy static_assert issue in more than one std lib impl, 
+// build a whitelist filter for the types that are allowed to be hashed 
+// in rxcpp. this allows is_hashable<T> to work.
+//
+// NOTE: this should eventually be removed!
+//
+template <class T, typename = void> 
+struct filtered_hash;
+template <class T> 
+struct filtered_hash<T, typename std::enable_if<std::is_enum<T>::value>::type> : std::hash<T> {
+};
+template <class T> 
+struct filtered_hash<T, typename std::enable_if<std::is_integral<T>::value>::type> : std::hash<T> {
+};
+template <class T> 
+struct filtered_hash<T, typename std::enable_if<std::is_pointer<T>::value>::type> : std::hash<T> {
+};
+
+template<typename, typename C = rxu::types_checked>
+struct is_hashable
+    : std::false_type {};
+
+template<typename T>
+struct is_hashable<T, 
+    typename rxu::types_checked_from<
+        typename filtered_hash<T>::result_type, 
+        typename filtered_hash<T>::argument_type, 
+        typename std::result_of<filtered_hash<T>(T)>::type>::type>
+    : std::true_type {};
+
 }
 
 #define RXCPP_UNWIND(Name, Function) \