From c40094a532f932bc0ed7af2279161dc4bc72b85d Mon Sep 17 00:00:00 2001
From: Neil MacIntosh <neilmac@microsoft.com>
Date: Tue, 1 Mar 2016 12:11:41 -0800
Subject: [PATCH] Added from-container constructors.

---
 include/multi_span.h        | 18 ++++++-------
 include/span.h              | 50 +++++++++++++++++++++++++++++++------
 include/string_span.h       | 28 ++++++++++-----------
 tests/span_tests.cpp        |  4 +--
 tests/string_span_tests.cpp |  2 +-
 5 files changed, 68 insertions(+), 34 deletions(-)

diff --git a/include/multi_span.h b/include/multi_span.h
index b070f29..5eb9109 100644
--- a/include/multi_span.h
+++ b/include/multi_span.h
@@ -1156,22 +1156,22 @@ namespace details
     };
 
     template <typename T>
-    struct is_span_oracle : std::false_type
+    struct is_multi_span_oracle : std::false_type
     {
     };
 
     template <typename ValueType, std::ptrdiff_t FirstDimension, std::ptrdiff_t... RestDimensions>
-    struct is_span_oracle<multi_span<ValueType, FirstDimension, RestDimensions...>> : std::true_type
+    struct is_multi_span_oracle<multi_span<ValueType, FirstDimension, RestDimensions...>> : std::true_type
     {
     };
 
     template <typename ValueType, std::ptrdiff_t Rank>
-    struct is_span_oracle<strided_span<ValueType, Rank>> : std::true_type
+    struct is_multi_span_oracle<strided_span<ValueType, Rank>> : std::true_type
     {
     };
 
     template <typename T>
-    struct is_span : is_span_oracle<std::remove_cv_t<T>>
+    struct is_multi_span : is_multi_span_oracle<std::remove_cv_t<T>>
     {
     };
 }
@@ -1324,7 +1324,7 @@ public:
     // type-requirements: container must have .size(), operator[] which are value_type compatible
     template <typename Cont, typename DataType = typename Cont::value_type,
               typename = std::enable_if_t<
-                  !details::is_span<Cont>::value &&
+                  !details::is_multi_span<Cont>::value &&
                   std::is_convertible<DataType (*)[], value_type (*)[]>::value &&
                   std::is_same<std::decay_t<decltype(std::declval<Cont>().size(),
                                                      *std::declval<Cont>().data())>,
@@ -1338,7 +1338,7 @@ public:
     // prevent constructing from temporary containers
     template <typename Cont, typename DataType = typename Cont::value_type,
               typename = std::enable_if_t<
-                  !details::is_span<Cont>::value &&
+                  !details::is_multi_span<Cont>::value &&
                   std::is_convertible<DataType (*)[], value_type (*)[]>::value &&
                   std::is_same<std::decay_t<decltype(std::declval<Cont>().size(),
                                                      *std::declval<Cont>().data())>,
@@ -1595,7 +1595,7 @@ template <typename SpanType, typename... Dimensions2, size_t DimCount = sizeof..
 constexpr multi_span<typename SpanType::value_type, Dimensions2::value...> as_span(SpanType s,
                                                                              Dimensions2... dims)
 {
-    static_assert(details::is_span<SpanType>::value,
+    static_assert(details::is_multi_span<SpanType>::value,
                   "Variadic as_span() is for reshaping existing spans.");
     using BoundsType =
         typename multi_span<typename SpanType::value_type, (Dimensions2::value)...>::bounds_type;
@@ -1718,7 +1718,7 @@ constexpr multi_span<T, dynamic_range> as_span(T* begin, T* end)
 
 template <typename Cont>
 constexpr auto as_span(Cont& arr) -> std::enable_if_t<
-    !details::is_span<std::decay_t<Cont>>::value,
+    !details::is_multi_span<std::decay_t<Cont>>::value,
     multi_span<std::remove_reference_t<decltype(arr.size(), *arr.data())>, dynamic_range>>
 {
     Expects(arr.size() < PTRDIFF_MAX);
@@ -1727,7 +1727,7 @@ constexpr auto as_span(Cont& arr) -> std::enable_if_t<
 
 template <typename Cont>
 constexpr auto as_span(Cont&& arr) -> std::enable_if_t<
-    !details::is_span<std::decay_t<Cont>>::value,
+    !details::is_multi_span<std::decay_t<Cont>>::value,
     multi_span<std::remove_reference_t<decltype(arr.size(), *arr.data())>, dynamic_range>> = delete;
 
 // from basic_string which doesn't have nonconst .data() member like other contiguous containers
diff --git a/include/span.h b/include/span.h
index 2d95899..eab2659 100644
--- a/include/span.h
+++ b/include/span.h
@@ -72,12 +72,35 @@
 namespace gsl
 {
 
+template <class ElementType, std::ptrdiff_t Extent = dynamic_extent>
+class span;
+
+
+namespace details
+{
+template <class T>
+struct is_span_oracle : std::false_type
+{
+};
+
+template <class ElementType, std::ptrdiff_t Extent>
+struct is_span_oracle<gsl::span<ElementType, Extent>> : std::true_type
+{
+};
+
+template <class T>
+struct is_span : is_span_oracle<std::remove_cv_t<T>>
+{
+};
+} // namespace details
+
+
 // [views.constants], constants  
 constexpr const std::ptrdiff_t dynamic_extent = -1;
 
 
 // [span], class template span 
-template <class ElementType, std::ptrdiff_t Extent = dynamic_extent>
+template <class ElementType, std::ptrdiff_t Extent>
 class span {
 public:
     // constants and types 
@@ -122,11 +145,25 @@ public:
         : storage_(&arr[0], extent_type<N>())
     {}
 
-#if 0 // TODO
-    template <class Container>
-    constexpr span(Container& cont);
-    template <class Container>
+    // NB: the SFINAE here uses .data() as a incomplete/imperfect proxy for the requirement
+    // on Container to be a contiguous sequence container.
+    template <class Container,
+        class = std::enable_if_t<!details::is_span<Container>::value &&
+        std::is_convertible<Container::pointer, pointer>::value &&
+        std::is_convertible<Container::pointer, decltype(std::declval<Container>().data())>::value>
+    >
+    constexpr span(Container& cont) : span(cont.data(), cont.size()) {}
+
+    // NB: the SFINAE here uses .data() as an incomplete/imperfect proxy for the requirement
+    // on Container to be a contiguous sequence container.
+    template <class Container,
+        class = std::enable_if_t<!details::is_span<Container>::value &&
+        std::is_convertible<Container::pointer, pointer>::value &&
+        std::is_convertible<Container::pointer, decltype(std::declval<Container>().data())>::value>
+    >
     span(const Container&&) = delete;
+    
+#if 0 // TODO
     constexpr span(const span& other) noexcept = default;
     constexpr span(span&& other) noexcept = default;
     template <class OtherElementType, ptrdiff_t OtherExtent>
@@ -231,9 +268,6 @@ private:
         storage_type(pointer data, OtherExtentType ext)
             : ExtentType(ext), data_(data) {}
 
-        //storage_type(pointer data, ExtentType ext)
-        //    : ExtentType(ext), data_(data) {}
-        
         constexpr inline pointer data() const noexcept
         { return data_; }
 
diff --git a/include/string_span.h b/include/string_span.h
index c58cef9..69c3a81 100644
--- a/include/string_span.h
+++ b/include/string_span.h
@@ -297,7 +297,7 @@ public:
 
     // from containers. Containers must have .size() and .data() function signatures
     template <typename Cont, typename DataType = typename Cont::value_type,
-        typename Dummy = std::enable_if_t<!details::is_span<Cont>::value
+        typename Dummy = std::enable_if_t<!details::is_multi_span<Cont>::value
         && !details::is_basic_string_span<Cont>::value
         && !(!std::is_const<value_type>::value && std::is_const<Cont>::value) // no converting const containers to non-const span
         && std::is_convertible<DataType*, value_type*>::value
@@ -309,7 +309,7 @@ public:
 
     // disallow creation from temporary containers and strings
     template <typename Cont, typename DataType = typename Cont::value_type,
-        typename Dummy = std::enable_if_t<!details::is_span<Cont>::value
+        typename Dummy = std::enable_if_t<!details::is_multi_span<Cont>::value
         && !details::is_basic_string_span<Cont>::value
         && std::is_convertible<DataType*, value_type*>::value
         && std::is_same<std::decay_t<decltype(std::declval<Cont>().size(), *std::declval<Cont>().data())>, DataType>::value>
@@ -640,7 +640,7 @@ bool operator==(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -654,7 +654,7 @@ bool operator==(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -694,7 +694,7 @@ bool operator!=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -707,7 +707,7 @@ bool operator!=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -748,7 +748,7 @@ bool operator<(const T& one, gsl::basic_string_span<CharT, Extent> other) noexce
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -762,7 +762,7 @@ bool operator<(gsl::basic_string_span<CharT, Extent> one, const T& other) noexce
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -802,7 +802,7 @@ bool operator<=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -815,7 +815,7 @@ bool operator<=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -854,7 +854,7 @@ bool operator>(const T& one, gsl::basic_string_span<CharT, Extent> other) noexce
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -867,7 +867,7 @@ bool operator>(gsl::basic_string_span<CharT, Extent> one, const T& other) noexce
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -906,7 +906,7 @@ bool operator>=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexc
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
@@ -919,7 +919,7 @@ bool operator>=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexc
 template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_range, typename T,
     typename DataType = typename T::value_type,
     typename Dummy = std::enable_if_t<
-    !gsl::details::is_span<T>::value
+    !gsl::details::is_multi_span<T>::value
     && !gsl::details::is_basic_string_span<T>::value
     && std::is_convertible<DataType*, CharT*>::value
     && std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>, DataType>::value>
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
index e13694c..e68493c 100644
--- a/tests/span_tests.cpp
+++ b/tests/span_tests.cpp
@@ -438,7 +438,7 @@ SUITE(span_tests)
         }
 #endif
     }
-#if 0
+
     TEST(from_container_constructor)
     {
         std::vector<int> v = {1, 2, 3};
@@ -512,7 +512,7 @@ SUITE(span_tests)
 #endif
         }
     }
-
+#if 0
     TEST(from_convertible_span_constructor)
     {
 #ifdef CONFIRM_COMPILATION_ERRORS
diff --git a/tests/string_span_tests.cpp b/tests/string_span_tests.cpp
index cd301a0..6876253 100644
--- a/tests/string_span_tests.cpp
+++ b/tests/string_span_tests.cpp
@@ -46,7 +46,7 @@ SUITE(string_span_tests)
     TEST(TestConstructFromStdVector)
     {
         std::vector<char> vec(5, 'h');
-        string_span<> v = vec;
+        string_span<> v {vec};
         CHECK(v.length() == static_cast<string_span<>::size_type>(vec.size()));
     }