[libsigc++2] C++11: deduce_result_type.h: Add and use a deduce_result_t<> alias.

[Murray Cumming <murrayc src gnome org>]

commit 0590de0f5232ef9b77cb3e1969035430cf608862
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Aug 13 11:57:06 2015 +0200

    C++11: deduce_result_type.h: Add and use a deduce_result_t<> alias.
    
    This simplifies the code a bit, by replacing use of this:
      typename deduce_result_type<SomeType1, SomeType2>::type
    with this:
      deduce_result_t<SomeType1, SomeType2>
    
    Note that the alias is a C++11 variadic template.
    Bug #753580

 sigc++/adaptors/macros/adaptor_trait.h.m4      |    4 ++--
 sigc++/adaptors/macros/compose.h.m4            |   12 ++++++------
 sigc++/adaptors/macros/deduce_result_type.h.m4 |    4 ++++
 3 files changed, 12 insertions(+), 8 deletions(-)
---
diff --git a/sigc++/adaptors/macros/adaptor_trait.h.m4 b/sigc++/adaptors/macros/adaptor_trait.h.m4
index 3522d7d..a7a0613 100644
--- a/sigc++/adaptors/macros/adaptor_trait.h.m4
+++ b/sigc++/adaptors/macros/adaptor_trait.h.m4
@@ -134,7 +134,7 @@ struct adaptor_functor : public adaptor_base
 #ifndef DOXYGEN_SHOULD_SKIP_THIS
   template <LOOP(class T_arg%1=void, CALL_SIZE)>
   struct deduce_result_type
-    { typedef typename sigc::deduce_result_type<LIST(T_functor, LOOP(T_arg%1,CALL_SIZE))>::type type; };
+    { typedef sigc::deduce_result_t<LIST(T_functor, LOOP(T_arg%1,CALL_SIZE))> type; };
 #endif
   typedef typename functor_trait<T_functor>::result_type result_type;
 
@@ -259,7 +259,7 @@ struct adaptor_trait<T_functor, false>
  * {
  *   template <class T_arg1=void, class T_arg2=void>
  *   struct deduce_result_type
- *   { typedef typename sigc::deduce_result_type<T_functor, T_arg1, T_arg2>::type type; };
+ *   { typedef sigc::deduce_result_t<T_functor, T_arg1, T_arg2> type; };
  *   typedef typename sigc::functor_trait<T_functor>::result_type result_type;
  *   //
  *   result_type
diff --git a/sigc++/adaptors/macros/compose.h.m4 b/sigc++/adaptors/macros/compose.h.m4
index 281acb9..6cd10db 100644
--- a/sigc++/adaptors/macros/compose.h.m4
+++ b/sigc++/adaptors/macros/compose.h.m4
@@ -22,7 +22,7 @@ define([COMPOSE1_OPERATOR],[dnl
   template <LOOP(class T_arg%1, $1)>
   typename deduce_result_type<LOOP(T_arg%1, $1)>::type
   operator()(LOOP(T_arg%1 _A_a%1, $1))
-    { return this->functor_.SIGC_WORKAROUND_OPERATOR_PARENTHESES<typename 
sigc::deduce_result_type<LIST(T_getter, LOOP(T_arg%1,$1))>::type>
+    { return this->functor_.SIGC_WORKAROUND_OPERATOR_PARENTHESES<sigc::deduce_result_t<LIST(T_getter, 
LOOP(T_arg%1,$1))>>
         (get_(LOOP(_A_a%1, $1)));
     }
 
@@ -32,8 +32,8 @@ define([COMPOSE2_OPERATOR],[dnl
   template <LOOP(class T_arg%1, $1)>
   typename deduce_result_type<LOOP(T_arg%1, $1)>::type
   operator()(LOOP(T_arg%1 _A_a%1, $1))
-    { return this->functor_.SIGC_WORKAROUND_OPERATOR_PARENTHESES<typename 
sigc::deduce_result_type<LIST(T_getter1, LOOP(T_arg%1,$1))>::type,
-                                                         typename sigc::deduce_result_type<LIST(T_getter2, 
LOOP(T_arg%1,$1))>::type>
+    { return this->functor_.SIGC_WORKAROUND_OPERATOR_PARENTHESES<sigc::deduce_result_t<LIST(T_getter1, 
LOOP(T_arg%1,$1))>,
+                                                         sigc::deduce_result_t<LIST(T_getter2, 
LOOP(T_arg%1,$1))>>
         (get1_(LOOP(_A_a%1, $1)), get2_(LOOP(_A_a%1,$1)));
     }
 
@@ -90,7 +90,7 @@ struct compose1_functor : public adapts<T_setter>
   template <LOOP(class T_arg%1 = void, CALL_SIZE)>
   struct deduce_result_type
     { typedef typename adaptor_type::template deduce_result_type<
-        typename sigc::deduce_result_type<LIST(T_getter, LOOP(T_arg%1,CALL_SIZE))>::type
+        sigc::deduce_result_t<LIST(T_getter, LOOP(T_arg%1,CALL_SIZE))>
           >::type type; };
 #endif
   typedef typename adaptor_type::result_type  result_type;
@@ -138,8 +138,8 @@ struct compose2_functor : public adapts<T_setter>
   template <LOOP(class T_arg%1=void, CALL_SIZE)>
   struct deduce_result_type
     { typedef typename adaptor_type::template deduce_result_type<
-        typename sigc::deduce_result_type<LIST(T_getter1, LOOP(T_arg%1,CALL_SIZE))>::type,
-        typename sigc::deduce_result_type<LIST(T_getter2, LOOP(T_arg%1,CALL_SIZE))>::type
+        typename sigc::deduce_result_t<LIST(T_getter1, LOOP(T_arg%1,CALL_SIZE))>,
+        typename sigc::deduce_result_t<LIST(T_getter2, LOOP(T_arg%1,CALL_SIZE))>
           >::type result_type; };
 #endif
   typedef typename adaptor_type::result_type  result_type;
diff --git a/sigc++/adaptors/macros/deduce_result_type.h.m4 b/sigc++/adaptors/macros/deduce_result_type.h.m4
index 5d3f4ed..2f5d70c 100644
--- a/sigc++/adaptors/macros/deduce_result_type.h.m4
+++ b/sigc++/adaptors/macros/deduce_result_type.h.m4
@@ -92,6 +92,10 @@ struct deduce_result_type
 
 #ifndef DOXYGEN_SHOULD_SKIP_THIS
 FOR(0,CALL_SIZE,[[DEDUCE_RESULT_TYPE_ADAPTOR(%1,CALL_SIZE)]])dnl
+
+template<typename... T>
+using deduce_result_t = typename deduce_result_type<T...>::type;
+
 #endif // DOXYGEN_SHOULD_SKIP_THIS
 
 dnl #ifdef SIGC_CXX_TYPEOF