[committed] libstdc++: Fix incorrect preprocessor conditions in <version>

[Jonathan Wakely <jwakely@redhat.com>]

Tested powerpc64le-linux, pushed to trunk.

-- >8 --

The conditions that guard the feature test macros in <version> should
match the main definitions of the macros in other headers.

This doesn't matter for GCC, because it supports all the conditions
being tested here, but it does matter for non-GCC compilers without the
relevant C++20 features.

libstdc++-v3/ChangeLog:

	* include/std/version (__cpp_lib_variant): Fix conditions to
	match <variant>.
	(__cpp_lib_expected): Fix condition to match <expected>.
---
 libstdc++-v3/include/std/version | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index 7dbac23f22d..44b8a9f88b5 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -176,7 +176,7 @@
 # define __cpp_lib_to_chars 201611L
 #endif
 #define __cpp_lib_unordered_map_try_emplace 201411L
-#if !(__cplusplus >= 202002L && __cpp_concepts >= 202002L)
+#if !(__cpp_concepts >= 202002L && __cpp_constexpr >= 201811L)
 // N.B. updated value in C++20
 # define __cpp_lib_variant 202102L
 #endif
@@ -293,7 +293,7 @@
 # endif
 #define __cpp_lib_to_address 201711L
 #define __cpp_lib_to_array 201907L
-#if __cplusplus >= 202002L && __cpp_concepts >= 202002L
+#if __cpp_concepts >= 202002L && __cpp_constexpr >= 201811L
 # define __cpp_lib_variant 202106L
 #endif
 #endif
@@ -306,7 +306,9 @@
 
 #if _GLIBCXX_HOSTED
 #define __cpp_lib_adaptor_iterator_pair_constructor 202106L
-#define __cpp_lib_expected 202202L
+#if __cpp_concepts >= 202002L
+# define __cpp_lib_expected 202202L
+#endif
 #define __cpp_lib_invoke_r 202106L
 #define __cpp_lib_ios_noreplace 202200L
 #if __cpp_lib_concepts
-- 
2.34.1