[libsigc++2/variadic] C++14 Remove now-unused deduce_result_t.

[Murray Cumming <murrayc src gnome org>]

commit f2a4c5eb03c56913050e5ffde88772d0aa4522d3
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Jan 8 11:58:12 2016 +0100

    C++14 Remove now-unused deduce_result_t.

 sigc++/adaptors/deduce_result_type.h |   46 +--------------------------------
 1 files changed, 2 insertions(+), 44 deletions(-)
---
diff --git a/sigc++/adaptors/deduce_result_type.h b/sigc++/adaptors/deduce_result_type.h
index 9717a7a..97b6f68 100644
--- a/sigc++/adaptors/deduce_result_type.h
+++ b/sigc++/adaptors/deduce_result_type.h
@@ -4,11 +4,10 @@
 
 namespace sigc {
 
+//TODO: Is this necessary now that we don't need deduce_result_type?
 /** A hint to the compiler.
  * Functors which have all methods based on templates
- * should publicly inherit from this hint and define 
- * a nested template class @p deduce_result_type that
- * can be used to deduce the methods' return types.
+ * should publicly inherit from this hint.
  *
  * adaptor_base inherits from the functor_base hint so
  * derived types should also have a result_type defined.
@@ -22,46 +21,5 @@ namespace sigc {
  */
 struct adaptor_base : public functor_base {};
 
-
-/** Deduce the return type of a functor.
- * <tt>typename deduce_result_type<functor_type, list of arg_types>::type</tt>
- * deduces a functor's result type if @p functor_type inherits from
- * sigc::functor_base and defines @p result_type or if @p functor_type
- * is actually a (member) function type. Multi-type functors are not
- * supported.
- *
- * sigc++ adaptors use
- * <tt>typename deduce_result_type<functor_type, list of arg_types>::type</tt>
- * to determine the return type of their <tt>templated operator()</tt> overloads.
- *
- * Adaptors in turn define a nested template class @p deduce_result_type
- * that is used by template specializations of the global deduce_result_type
- * template to correctly deduce the return types of the adaptor's suitable
- * <tt>template operator()</tt> overload.
- *
- * @ingroup adaptors
- */
-template<class T_functor, class... T_args>
-struct deduce_result_type
-{
-  //The compiler will choose this method overload if T_functor derives from adaptor_base,
-  //and if it has its own deduce_result_type member (which has its own ::type member).
-  template<class U_functor, typename = typename std::is_base_of<adaptor_base, T_functor>::type>
-  static
-  typename U_functor::template deduce_result_type<T_args...>::type
-  test();
-
-  //Otherwise, the compiler will choose this fallback method.
-  template<class U_functor>
-  static
-  typename functor_trait<T_functor>::result_type
-  test();
-
-  using type = decltype (test<T_functor> ());
-};
-
-template<typename T_functor, typename... T_args>
-using deduce_result_t = typename deduce_result_type<T_functor, T_args...>::type;
-
 } /* namespace sigc */
 #endif /* _SIGC_ADAPTORS_DEDUCE_RESULT_TYPE_H_ */