From 758ae808c0f527bfccd90cec8643dda5fbb60b94 Mon Sep 17 00:00:00 2001
From: Dmitry Anisimov <danston@ymail.com>
Date: Thu, 30 Jul 2020 17:33:00 +0200
Subject: [PATCH] better use of declval

---
 Filtered_kernel/include/CGAL/Lazy.h   | 22 +++++++++++-----------
 STL_Extension/include/CGAL/iterator.h |  8 +++++---
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/Filtered_kernel/include/CGAL/Lazy.h b/Filtered_kernel/include/CGAL/Lazy.h
index f348718c544..33228d1a0fd 100644
--- a/Filtered_kernel/include/CGAL/Lazy.h
+++ b/Filtered_kernel/include/CGAL/Lazy.h
@@ -398,7 +398,7 @@ public:
 };
 
 // Macro helpers to build the kernel objects
-#define CGAL_PARAM(z, n, t) t##n()
+#define CGAL_PARAM(z, n, t) std::declval<t##n>()
 #define CGAL_TYPEMAP_AC(z, n, t) typedef typename Type_mapper< t##n, LK, AK >::type A##n;
 #define CGAL_TYPEMAP_EC(z, n, t) typedef typename Type_mapper< t##n, LK, EK >::type E##n;
 #define CGAL_LEXACT(z,n,t) CGAL::exact( l##n )
@@ -1486,10 +1486,10 @@ struct Lazy_construction_variant {
   operator()(const L1& l1, const L2& l2) const {
     typedef typename result<Lazy_construction_variant(L1, L2)>::type result_type;
 
-    typedef decltype(std::declval<AC>()(typename Type_mapper<L1, LK, AK>::type(),
-                                        typename Type_mapper<L2, LK, AK>::type())) AT;
-    typedef decltype(std::declval<EC>()(typename Type_mapper<L1, LK, EK>::type(),
-                                        typename Type_mapper<L2, LK, EK>::type())) ET;
+    typedef decltype(std::declval<AC>()(std::declval<typename Type_mapper<L1, LK, AK>::type>(),
+                                        std::declval<typename Type_mapper<L2, LK, AK>::type>())) AT;
+    typedef decltype(std::declval<EC>()(std::declval<typename Type_mapper<L1, LK, EK>::type>(),
+                                        std::declval<typename Type_mapper<L2, LK, EK>::type>())) ET;
 
     CGAL_BRANCH_PROFILER(std::string(" failures/calls to   : ") + std::string(CGAL_PRETTY_FUNCTION), tmp);
     Protect_FPU_rounding<Protection> P;
@@ -1534,12 +1534,12 @@ struct Lazy_construction_variant {
   operator()(const L1& l1, const L2& l2, const L3& l3) const {
     typedef typename result<Lazy_construction_variant(L1, L2, L3)>::type result_type;
 
-    typedef decltype(std::declval<AC>()(typename Type_mapper<L1, LK, AK>::type(),
-                                        typename Type_mapper<L2, LK, AK>::type(),
-                                        typename Type_mapper<L3, LK, AK>::type())) AT;
-    typedef decltype(std::declval<EC>()(typename Type_mapper<L1, LK, EK>::type(),
-                                        typename Type_mapper<L2, LK, EK>::type(),
-                                        typename Type_mapper<L3, LK, EK>::type())) ET;
+    typedef decltype(std::declval<AC>()(std::declval<typename Type_mapper<L1, LK, AK>::type>(),
+                                        std::declval<typename Type_mapper<L2, LK, AK>::type>(),
+                                        std::declval<typename Type_mapper<L3, LK, AK>::type>())) AT;
+    typedef decltype(std::declval<EC>()(std::declval<typename Type_mapper<L1, LK, EK>::type>(),
+                                        std::declval<typename Type_mapper<L2, LK, EK>::type>(),
+                                        std::declval<typename Type_mapper<L3, LK, EK>::type>())) ET;
 
     CGAL_BRANCH_PROFILER(std::string(" failures/calls to   : ") + std::string(CGAL_PRETTY_FUNCTION), tmp);
     Protect_FPU_rounding<Protection> P;
diff --git a/STL_Extension/include/CGAL/iterator.h b/STL_Extension/include/CGAL/iterator.h
index dec026e4a43..8395606f4b5 100644
--- a/STL_Extension/include/CGAL/iterator.h
+++ b/STL_Extension/include/CGAL/iterator.h
@@ -659,7 +659,8 @@ class Join_input_iterator_1
 
 public:
   typedef typename std::iterator_traits<I1>::iterator_category  iterator_category;
-  typedef std::decay_t<decltype(std::declval<Op>()(arg_type()))> value_type;
+  typedef std::decay_t<decltype(std::declval<Op>()(std::declval<arg_type>()))>
+                                                                value_type;
   typedef typename std::iterator_traits<I1>::difference_type    difference_type;
   typedef value_type const*                                     pointer;
   typedef value_type const&                                     reference;
@@ -745,7 +746,8 @@ class Join_input_iterator_2
 
 public:
   typedef typename std::iterator_traits<I1>::iterator_category        iterator_category;
-  typedef decltype(std::declval<Op>()(arg_type_1(), arg_type_2()))    value_type;
+  typedef decltype(std::declval<Op>()(std::declval<arg_type_1>(), std::declval<arg_type_2>()))
+                                                                      value_type;
   typedef typename std::iterator_traits<I1>::difference_type          difference_type;
   typedef value_type*                                                 pointer;
   typedef value_type&                                                 reference;
@@ -839,7 +841,7 @@ class Join_input_iterator_3
 
 public:
   typedef typename std::iterator_traits<I1>::iterator_category  iterator_category;
-  typedef decltype(std::declval<Op>()(arg_type_1(), arg_type_2(), arg_type_3()))
+  typedef decltype(std::declval<Op>()(std::declval<arg_type_1>(), std::declval<arg_type_2>(), std::declval<arg_type_3>()))
                                                                 value_type;
   typedef typename std::iterator_traits<I1>::difference_type    difference_type;
   typedef value_type*                                           pointer;