Vendor import of libc++ release_40 branch r292951:

https://llvm.org/svn/llvm-project/libcxx/branches/release_40@292951

include/__config

@@ -103,6 +103,9 @@
 
 #if defined(__clang__)
 #define _LIBCPP_COMPILER_CLANG
+# ifndef __apple_build_version__
+#   define _LIBCPP_CLANG_VER (__clang_major__ * 100 + __clang_minor__)
+# endif
 #elif defined(__GNUC__)
 #define _LIBCPP_COMPILER_GCC
 #elif defined(_MSC_VER)
@@ -111,6 +114,10 @@
 #define _LIBCPP_COMPILER_IBM
 #endif
 
+#ifndef _LIBCPP_CLANG_VER
+# define _LIBCPP_CLANG_VER 0
+#endif
+
 // FIXME: ABI detection should be done via compiler builtin macros. This
 // is just a placeholder until Clang implements such macros. For now assume
 // that Windows compilers pretending to be MSVC++ target the microsoft ABI.
@@ -741,7 +748,7 @@ template <unsigned> struct __static_assert_check {};
 
 #ifdef _LIBCPP_HAS_NO_DECLTYPE
 // GCC 4.6 provides __decltype in all standard modes.
-#if !__is_identifier(__decltype) || _GNUC_VER >= 406
+#if !__is_identifier(__decltype) || _LIBCPP_CLANG_VER >= 304 || _GNUC_VER >= 406
 #  define decltype(__x) __decltype(__x)
 #else
 #  define decltype(__x) __typeof__(__x)
@@ -838,7 +845,7 @@ template <unsigned> struct __static_assert_check {};
 #if defined(__APPLE__)
 # if !defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && \
      defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__)
-#   define __MAC_OS_X_VERSION_MIN_REQUIRED __ENVIROMENT_MAC_OS_X_VERSION_MIN_REQUIRED__
+#   define __MAC_OS_X_VERSION_MIN_REQUIRED __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__
 # endif
 # if defined(__MAC_OS_X_VERSION_MIN_REQUIRED)
 #   if __MAC_OS_X_VERSION_MIN_REQUIRED < 1060

include/string

@@ -818,7 +818,10 @@ public:
     operator __self_view() const _NOEXCEPT { return __self_view(data(), size()); }
 
     basic_string& operator=(const basic_string& __str);
+
+#ifndef _LIBCPP_CXX03_LANG
     template <class = void>
+#endif
     _LIBCPP_INLINE_VISIBILITY
     basic_string& operator=(__self_view __sv)  {return assign(__sv);}
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES