From 99b07566f4e86f70ac2112a097e913ff180c9f20 Mon Sep 17 00:00:00 2001
From: huahang <huahang@users.noreply.github.com>
Date: Tue, 25 Aug 2020 09:14:38 +0800
Subject: [vcpkg] Fix build on old compilers. (#12950)

---
 toolsrc/include/vcpkg/base/expected.h | 3 ++-
 toolsrc/include/vcpkg/base/span.h     | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/toolsrc/include/vcpkg/base/expected.h b/toolsrc/include/vcpkg/base/expected.h
index d8a2cacaa..fcf37bcaf 100644
--- a/toolsrc/include/vcpkg/base/expected.h
+++ b/toolsrc/include/vcpkg/base/expected.h
@@ -4,6 +4,7 @@
 #include <vcpkg/base/stringliteral.h>
 
 #include <system_error>
+#include <type_traits>
 
 namespace vcpkg
 {
@@ -111,7 +112,7 @@ namespace vcpkg
         ExpectedT(S&& s, ExpectedRightTag = {}) : m_s(std::move(s)) { }
 
         ExpectedT(const T& t, ExpectedLeftTag = {}) : m_t(t) { }
-        template<class = std::enable_if<!std::is_reference_v<T>>>
+        template<class = std::enable_if<!std::is_reference<T>::value>>
         ExpectedT(T&& t, ExpectedLeftTag = {}) : m_t(std::move(t))
         {
         }
diff --git a/toolsrc/include/vcpkg/base/span.h b/toolsrc/include/vcpkg/base/span.h
index 221cccc8c..a66205332 100644
--- a/toolsrc/include/vcpkg/base/span.h
+++ b/toolsrc/include/vcpkg/base/span.h
@@ -3,6 +3,7 @@
 #include <array>
 #include <cstddef>
 #include <initializer_list>
+#include <type_traits>
 #include <vector>
 
 namespace vcpkg
@@ -29,7 +30,7 @@ namespace vcpkg
         {
         }
 
-        template<size_t N, class = std::enable_if_t<std::is_const_v<T>>>
+        template<size_t N, class = std::enable_if_t<std::is_const<T>::value>>
         constexpr Span(std::remove_const_t<T> (&arr)[N]) noexcept : m_ptr(arr), m_count(N)
         {
         }
-- 
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